Graybar 600 Service Notes

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Page 1

RADIO

GRAYBAR

600

SERVICE NOTES and

REPLACEMENT PARTS

......

..,

----=------

-).

GraybaR

ELECTRIC COMPANY

Page 2

AA+

Page 3

CONTENTS

Page

Introduction_

Radiotron Sequence

Service Data Chart....

Replacement Parts

40, 41, 42

PART I -INSTALLATION

Antenna (Outdoor Type)

Antenna (Indoor Type)

Special

Antenna Installations

for Noisy

Locations

Ground

Radiotrons

Receiving Loud Local Stations.

Page

Adjustment for Low Line Voltages__ ___

"Local -Distant" Switch________

.....

....

12'

Jerky Action of Station Selector................._______

Installation of Pilot

......

Phonograph Pick -Up....

Location of Receiver in Room.

Knobs

PART II -SERVICE DATA

Antenna System Failures

Radiotron Sockets

Radiotron Prongs

Loose Volume Control

Broken Condenser Drive Cord

Radiotrons Fail to Light When Operating

Switch Is "On" ___-_____ .....

......

Plates of Radiotron UX-280 Excessively Hot

No Signal-Radiotrons 0 K.

Hum

Low Volume

Audio Howl

Acoustic Howl ..

Distortion in Reproducer Unit Only

Adjustment

of R.F.

Compensating Con -

denser

- 18

Distorted Reproduction Caused by Other

Than Reproducer Unit

- 18

Adjustment of I.F. Transformers

Adjustment of

Oscillator Trimming Con -

Testing

Electrical Alignment

of Tuning

Condensers

Audio Transformer and Receiver By-Pass,

Condensers

Output Condenser, Output Choke and Filter

Condensers

Reproducer Unit ..

Centering Cone of Reproducer Unit

PART III -ELECTRICAL TESTS

Voltage Supply System

Voltage Readings at Terminal Strip

Voltage Readings at Radiotron Sockets

Methods for Continuity Tests

Receiver Assembly Continuity Tests

Socket Power Unit Continuity Tests _

Checking Resistance Values

Testing By -Pass Condensers

Testing

for Grounded Parts in Receiver

Assembly

PART IV -MAKING REPLACEMENTS

Replacing the Volume Control

Replacing R.F. Transformer and Oscillator

Assembly

Replacing Radiotron Gang Sockets

Replacing Main Tuning

Condensers

and

Drive

Replacing Condenser Drive Cord ...........

Replacing R.F. Compensating and Oscillator

Trimming Condensers ... ......

..........

.......

Replacing the Audio Transformer and By -

Pass Condensers

.....

....... _ ......

....... ......

Replacing Perforated Dial Scale

Replacing Power Cable

Replacing Intermediate Transformers

Model No. 600 Receiver

Rear Interior Cabinet View

Top View of Receiver Chassis

Top View of S.P.U.

Radiotron Sequence

Sub -Chassis View of Receiver

Schematic Circuit of No. 600 Receiver

10-11

Dial Screen, Tuning Scale, and Pilot Lamp

Schematic of Phonograph Pick -Up

Tuning Condenser Drive Cord

Non -Metallic Screw Driver

Adjusting Compensating and Oscillator Trim-

ming Condensers

175 K.C. Test Oscillator

Adjusting

I.F.

Tuning and

Neutralizing.

Condensers

22 23 23

Replacing Tapped Resistance Unit in Receiver

Assembly

Replacing Miscellaneous Parts in Receiver

Assembly

Replacing Cone of Reproducer Unit

Replacing Output Transformer

34 Replacing Filter Condensers, Output Con-

denser and Output Choke

Replacing Power Transformer or Filter Re -

Replacing Terminal Strip on S.P.U. or Re -

ceiver Assembly

Replacing Miscellaneous Parts in S.P.U.

Replacing Front Grill Panel or Cloth...._....-...........

ILLUSTRATIONS

36 36 37

38 38

I.F.Condenser Adjusting Screws

Adjusting Oscillator Trimming Condensers

Aligning Tuning Condensers

Aligning Tool

Centering Cone

Schematic of Voltage Supply System

Internal Connections of Audio Transformer

and By -Pass Condensers

Internal Connections of Output Choke, Out-

put Condenser and Filter Condensers .

Cable Connections

Receiver Sub -Chassis Wiring Diagram .........-. .... 28

S.P.U. Wiring Diagram

Removing Reproducer from Cabinet.. 32

Removing Receiver from Cabinet

Removing Grill Panel from Cabinet

Page 4

SOCKET POWER

UNIT

SPARE PILOT

LAMP SOCKET

ANTENNA AND

GROUND

BINDING POSTS

Figure 1-Rear interior cabinet view showing

location of main assemblies

DYNAMIC REPRODUCER

ASSEMBLY

RECEIVER CHASSIS

ASSEMBLY

Page 5

Grayb aR

No. 600 RECEIVER

SERVICE NOTES

INTRODUCTION

The Graybar No. 600 receiver is a seven -tube socket powered console

cabinet model

radio receiver utilizing the Super -Heterodyne circuit in its highest development,

and em-

ploying six UY-227 Radiotrons and the newly developed power amplifier

Radiotron, UX-245.

The Radiotron UX-280 is used in a socket power unit for supplying all

plate, grid, and

cathode voltages as well as supplying a high D.C. voltage for the newly

developed high

voltage, low current dynamic reproducer field used in this receiver.

Incorporated in this

receiver are the latest developments in Super -Heterodyne

engineering in addition to other

perfected features such as one -dial control, complete A.C. operation, power

detection, single

audio amplification stage, with overall balance in sensitivity, selectivity and

tonal quality

that can best be accomplished in a Super -Heterodyne.

Figure 1 illustrates a rear view show-

ing the principal parts.

Figure 2 illustrates the top view of the receiver chassis,

and Figure

3 is a view of the socket poiyer unit.

PERFORAtED

CELLULOID

DIAL

DIAL SCREEN

STATION

SELECTOR DRIVE

ANTENNA AND

GROUND LEADS

PILOT

GANG CONDENSER

A. F. TRANSFORMER AND

LAMP

ASSEMBLY

BY-PASS CONDENSERS

CABLE TO S. P. U.

SERIAL

R. F. COMPENSATING

SERIES OSCILLATOR

PARALLEL OSCILLATOR

PHONOGRAPH PICK-UP

NUMBER

CONDENSER

TRIMMING COND. (600 K. C.)

TRIMMING COND. (1400 K. C)

TERMINAL STRIP

Figure 2-Top view of receiver chassis showing principal parts

The No. 600 receiver is designed to operate on alternating current of

105 to 125 volts,

50 to 60 cycles as used for house lighting.

Connection to D.C. lines or to A.C. lines of

different rating may damage the receiver or the Radiotrons.

This receiver is also made in models designed for alternating current operation

of 105

to 125 volts, 25 to 40 cycles.

In this model the power transformer is different from that

used in the 50-60 cycle models.

All other parts are identical in both models and the Service

Notes apply to each equally well.

The following circuit characteristics are incorporated in the No. 600

receiver:

(a) The six UY-227 Radiotrons and one UX-245 Radiotron are connected in a seven -

tube super -heterodyne circuit with a UX-280 Radiotron in the S.P.U. for plate,

grid, and cathode voltage supply as well as high voltage, low current supply to the

field of the new dynamic speaker.

Page 6

The super -heterodyne circuit consists of one tuned R.F. stage; tuned fitst de-

tector; two intermediate R.F. stages; an oscillator; a second, or power detector;

and the single audio stage using the recently developed power amplifier litictiotron

UX-245.

The Radiotron sequence is shown in Figure 4.

(b) A "Local -Distant" antenna switch is incorporated in this receiver which permits

better control of volume with less distortion, due to the natural condition of over-

loading on extremely loud local signals together with better selectivity on local

stations.

This feature with the use of a high impedance semi -tuned primary induct-

ance of the tuned R.F. stage permits the use of a varying length of antenna without

materially affecting the tuning of the receiver.

mixing of the incoming modulated radio frequency current with that of the local

oscillator is 175 K.C. The audio, or voice, modulation that is present in the radio

frequency is carried on through the first detector and in the mixing is impressed

on the I.F.

After being amplified in two I.F. stages it is detected, or rectified, and

POWER

OUTPUT CHOKE, OUTPUT CONDENSER,.

TRANSFORMER

AND FILTER CONDENSERS

FILTER

REACTORS

TERMINAL

STRIP

A. C. POWER INPUT UNE

UK -280

OPERATING

(PLUG NOT SHOWN)

SOCKET

SWITCH

Figure 3-Socket power unit showing

principal parts

further amplified in the audio amplifier stage using the new Radiotron UX-245.

'I'he use of 175 K.C. for the I.F. prevents serious harmonic disturbance around

550 K.C., which is a distinct asset.

The super -heterodyne circuit owes its superior

selectivity and sensitivity to tuned I.F. amplification, for no matter what the R.F.

frequency may be to which the receiver may be tuned the most part of the over-all

amplification is accomplished by the uniform amplification of the I.F. stages.

These

I.F. stages are also constantly neutralized for 175 K.C.

Neutralization, or preven-

tion of oscillation, is then independent of the broadcast frequency, which is

prac-

tically the ideal condition for radio reception.

The I.F. transformers are sharply

tuned to give improved over-all selectivity.

The tonal quality is maintained by

means of certain refinements in the circuit arrangement, especially at high fre-

quencies.

(d) The second detector operates at 235 volts plate potential with proper grid bias.

The high plate voltage used gives sufficient undistorted output to operate the single

audio power stage using the UX-245 Radiotron directly from the second detector,

thus eliminating any possible distortion that might be caused by an intermediate

audio stage.

(e) Use of the UX-245 Radiotron with the new dynamic speaker permits

an undistorted

output which represents an over-all gain over previous receivers.

It uses the same

Page 7

( f )

(g)

voltage on its filament as the UY-227, and plate and grid voltages that fall within

the supply limits of a UX-280.

The volume control regulates the grid bias on the tuned R.F. stage and the first

I.F. stage. When loud local signals are received the "Local -Distant" switch in the

local position acts very effectively in allowing better control of volume near the

maximum volume control setting without over -loading the receiver.

The volume,

when the over -loading point is reached, will, of course, distort and drop to a small

value. This is entirely natural to the over -loading condition in a vacuum tube, as

is also the two peaked tuning effect, which is obtained when the dial is detuned to

either side of the normal peak setting with resultant less input and hence no over-

The use of a high voltage, low current field in the dynamic loudspeaker employing

the 8 -inch cone makes a sensitive reproducer with a field that is supplied by the total

D.C. voltage output of the UX-280 in the S.P.U., drawing only approximately 46

milliamperes at about 300 volts.

This load together with the receiver Radiotron load

is much below the load limit of the UX-280. The voltages on the plates, as well as

the grid voltages of the R.F. and I.F. Radiotrons, are purposely reduced to make no

over-all difference in amplification, but permitting better S.P.U. regulation and

stabler operation.

Proper cathode voltages are supplied to all the UY-227 Radio -

FROM ANTENNA

POWER

2.20iTPWR.)

OSC.

F. LE I. F.

TUNED IL' TUNED

A. F.

DET.

R. F.

RADIO FREQUENCY CURRENT

-- -

OSCILLATOR

R. F. CURRENT IN INTERMEDIATE STAGES

LOUDSPEAKER

A. F CURRENT

Figure 4-Radiatron sequence

trons to secure quiet operation and insure average Radiotron life.

For the most

part, the series or parallel resistance method of supplying voltages is used.

The

line voltage adjustment switch, common in most receivers, has been discarded to

make necessary a more careful check of the supply line voltage before making any

change. A tap has been provided in the power transformer primary, located under

the S.P.U. for lower than 115 -volt power supply to which a soldered connection can

be made.

This will prevent frequent change -over in the power supply and thus

will lessen the application of excessive filament voltages.

Mechanical and electrical improvements not mentioned above are :-

(a) Use of "Isolantite" for I.F. transformer adjustable condenser and coil mounting,

and also the R.F. compensating and oscillator trimming condenser mounting.

(b) Accessibility of I.F. adjustments.

See Part II, Section 16.

also between socket power unit and receiver chassis.

(d) Simplified construction of the S.P.U. (e) Projection type of dial scale with kilocycle designation is distinctly a new feature.

(f) A terminal strip is provided for convenient use of a phonograph pick-up.

RADIOTRON SEQUENCE

Figure 4 illustrates the Radiotron sequence.

Radiotron No. 1 is a stage of tuned radio

frequency amplification.

It is coupled to the antenna and ground by a high impedance

primary inductive coil.

It is tuned by the first of the gang condensers located at the right

and facing the receiver from the front.

Radiotron No. 2 is the tuned heterodyne detector.

It is tuned by the center of the gang

condensers.

Page 8

Radiotrons No. 3 and No 4 are the first and second intermediate frequency stages re-

spectively. These stages are tuned to a frequency of 175 K.C., giving ample distance between

the two peaks of the oscillator to eliminate any possibility of stations coming in at more than

one point on the tuning dial.

Radiotron No. 5 is the oscillator.

It is tuned by the third of the gang condensers. Two

trimming condensers are provided at the rear of the receiver assembly for adjusting the oscillator circuit to keep the beat note at the correct frequency for the intermediate fre-

quency stages.

Radiotron No. 6 is the second detector.

It operates at a plate potential of 235 volts

with the proper grid bias and does not use a grid leak or condenser.

Its output is sufficient

to drive the power amplifier.

Radiotron No. 7 is the power amplifier. A choke and condenser arrangement couples

this tube to the step-down transformer that matches the impedance of the output circuit to

that of the cone coil of the reproducer unit.

This arrangement gives a quality of repro-

duction not obtainable with the use of an output transformer alone, and prevents flow of the

D.C. plate current of the UX-245 through the output transformer primary.

These various principles incorporated in the No. 600 receiver are illustrated in the

schematic circuit Figure 6.

PART I-INSTALLATION

[ 1

ANTENNA (OUTDOOR TYPE)

Due to the high sensitivity of this receiver the antenna length need be only 25 to 50

feet. In remote districts this length may be extended to secure improved pick-up of distant

broadcasting stations. However, a natural corresponding decrease in selectivity when receiv-

ing from local stations will be experienced with the longer antenna, provided the "Local

Distant" switch is not in the local position.

It should be erected as high as possible and be removed from all obstructions.

The

lead-in should be a continuation of the antenna itself, thus avoiding all splices which might

introduce additional resistance and, in time, corrode sufficiently to seriously affect reception.

If it is absolutely necessary to splice the lead-in to the antenna the joint must be carefully

soldered to insure a good electrical contact.

Clean off all excess flux and tape the connection,

to protect it from the oxidation effects of the atmosphere.

High-grade glass or porcelain insulator supports are required, and at no point should the

antenna or lead-in wire come in contact with any part of the building.

Bring the lead-in

wire from the outside through a porcelain tube insulator to the inside of the house for con-

nection to the receiver.

The antenna should not cross either over or under any electric light, traction, or power

line and should be at right angles to these lines and other antennas. An outdoor antenna should be protected by means of an approved lightning arrester, in accordance with the

requirements of the National Fire Underwriters' Code.

[ 2 ] ANTENNA (INDOOR TYPE)

Where the installation of an outdoor antenna is not practical, satisfactory results may

generally be obtained by using an indoor antenna of 25 to 50 feet of insulated wire strung around the picture moulding or placed under a rug.

In buildings with steel framework or

where metal lathing is employed, satisfactory results are not always possible with this type

of antenna.

However, due to its sensitivity, the No. 600 receiver will generally give entirely

satisfactory reception with an indoor antenna.

[ 3 ] SPECIAL ANTENNA INSTALLATIONS FOR NOISY

LOCATIONS

In line with other receivers, when the No. 600 receiver is installed in some city locations,

such as apartment houses, hotels and office buildings, it is possible that the level of noise

compared with the signal strength of the desired station may be such that the station cannot

be received without an objectionable noise background. This noise may be defined as inductive

interference from electrical devices such as elevator motors, generators, violet ray machines,

professional equipment, etc.

It may have no apparent radio frequency peak, or it may have

a broad peak. The effect of the noise may be divided into the following three general classes :

Page 9

(a) Where the noise level is zero with no antenna or ground, but is equally great on

either an indoor or outdoor antenna.

(b) Where the noise is equally great with the antenna and ground either connected or

disconnected.

an inside antenna is used ; the inside antenna, however, not giving

sufficient pick-up

for satisfactory reception.

In (a) where the noise level is zero with no antenna or ground connected, but equally

great with either an indoor or outdoor antenna, it is at once apparent that the interference

is not being brought into the receiver over the power supply lines.

It has been found in

such cases that an antenna five feet long inside the room picked up as much noise as when

an entire outside antenna lead -in were used.

This indicates that the noise is within the

building and, in the case of the outside antenna, is being picked up on that portion of the

lead-in that enters and goes through the building.

In such cases the receiver should be

located close to the point where the outside lead-in enters the building.

If this is impractical

it can be placed in any location and a copper braid, such as that manufactured by Belden

Mfg. Co. of Chicago, Ill., placed over the inside portion of the lead-in wire.

This braid is

not grounded.

If the noise level is still appreciable a good receiver ground with a short lead

must be obtained. A long lead is not desirable, as it may pick up noise.

R. F. AND OSCILLATOR

COIL ASSEMBLY

GROUND CONNECTION

TO FRAME

ANTENNA

GROUND

LEAD

RESISTOR

DIVIDING RES.

I. F. TRANSFORMERS

RESISTOR

OSCILLATOR

OSCILLATOR SERIES

R. F. BY PASS

UX-245 GRID

GRID CONDENSER FIXED CONDENSER

CONDENSER

BIAS RESISTOR

OSCILLATOR

FILAMENT CENTER -

GRID LEAK

GRID RESISTOR

TAPPED RESISTOR

F. TRANSF.

PRI. RESISTOR

A. F. TRANSF

SECONDARY

CONDENSER

A. F. TRANSF

SEC. SERIES

RESISTOR

BLEEDER

VOLTAGE N2 1 AND N. 2

YE' I. F. PRI. ti

\ VOLUME

Ne 3 I. F.

CONTROL TRANSFORMER

Figure 5--Sub-chassis view of receiver showing principal parts

In (b) the noise is picked up with no antenna or ground connected to the receiver. This

indicates the noise is entering the receiver through the power lines.

In this case filters must

be placed in the power supply at the source of the noise or at the receiver, depending on

conditions.

If the trouble is cleared up in this manner when the antenna and ground are

disconnected, but again appears with the use of the antenna system, the remedies suggested

in (a) must also be applied.

In (c) the noise is greater when the outside antenna is connected than when an inside

antenna is used. The use of the inside antenna, however, does not give sufficient pick-up for

satisfactory reception.

In this case the pick-up is probably occurring on the lead-in wire

between the receiver and the antenna.

Copper braid should be placed over the entire lead-in

from the receiver to the flat portion of the antenna.

Also changing the direction of the

antenna should be tried and the lead-in connected from the end of the antenna that gives

the best results.

The copper braid should not be grounded. The conditions existing in any

locality must be analyzed and placed in its correct category. A little patience and experi-

menting will usually result in a satisfactory installation.

RCA type "A" line filters may be used where the interfering line apparatus draws up

to 2.5 amperes at 110 volts A.C. or D.C.

For larger apparatus drawing current from 2.5

amperes to 5.0 amperes, RCA type "B" line filter may be used.

Page 10

[ 4 ] GROUND

A good ground is quite as important as a good antenna.

No specific recommendations

can be given in this matter as conditions vary in different locations. Water and steam pipes

usually make good grounds. Gas pipes usually make

poor grounds and, as a rule, are to be

avoided. If neither water nor steam pipes

are available, a pipe or metal rod may be driven

into the ground to a depth of several feet. The success of this type of ground depends

upon

the moisture present in the soil.

The ground lead should be as short as possible and con-

nected by means of an approved ground clamp to

a section of pipe that has been scraped and

thoroughly cleaned. The connection should be inspected from time

to time to make certain

that a clean and tight electrical contact exists between the clamp and pipe. The service

man

should experiment with various grounds, and employ the

one giving the best results.

icy

LOCAL -DISTANT

/SWITCH

UY 227

TUNED R f

R F

COMPENSATING

CONDENSER--_

g g

c=i

.___If.

0.5

MFD-

UT 227

DET

GROUND LEAD AND

ALL OTHER GROUND

CONNECTIONS ARE

CONNECTED TO FRAME

0.0008

MFD

3,00011

UT 227

OSC

[ 5 ] RADIOTRONS

A guide shield is provided on all the receiver Radiotron sockets to facilitate the insertion

of the Radiotrons. The six Radiotrons UY-227 are inserted in the five -contact sockets. The

Radiotron UX-245 is placed in the four -contact socket in the receiver assembly, and the

Radiotron UX-280 is placed in the socket power unit.

In placing the receiver into operation, if no signals are heard when tuning to a station

known to be broadcasting, examine the Radiotrons.

Possibly one Radiotron has been dam-

aged in transit.

Interchanging with one or more of the same type known to be in operating

condition will isolate the damaged one.

NoTE.-Socket No. 1 (Figure 4), the tuned R.F. stage, is the most critical for selection

of the Radiotrons.

Place in this socket the tube which gives the loudest signal and does not

go into oscillation throughout the tuning range.

If no tube is found that will not oscillate,

a slight re -adjustment of the R.F. compensating condenser may be necessary, as described in

Part II, Section 14.

PILOT

LAMP

UT-227

UY-227

2'2 I. F

0.5

37511

VOLUME

CONTROL

55011

9011

0.5 MFD.

6,000.n.

LINK

LINK AND CONNECTIONS

FOR

PHONOGRAPH PICK-UP

(LINK OPEN FOR PICKUP

USE, SEE PART 1, SECA()

Figure 6-Schematic circuit diagram of No. 600 receiver

Page 11

Other stages somewhat critical are the oscillator and second detector, sockets No.

5 and

No. 6 respectively. The remaining tubes should be interchanged until a tube is found for the

oscillator that gives the loudest signal on a given station.

The second detector Radiotron

should be selected for its ability to handle large volume.

Select the tube for this socket that

will permit the volume control to be advanced and give the greatest undistorted output with-

out overloading.

The I.F. stages, Radiotrons No. 3 and No. 4, should have tubes chosen for best ampli-

fication. When changing Radiotrons it is advisable to change one at a time, so that no un-

necessary voltage unbalancing will result.

Turn operating switch "Off" when changing

UX-280.

UY.227

2.° (PWR.) DET

0.5 11,11FD.

40,00011 .00016

UX-245

MFD.

PWR. A. F

FIELD

COIL

MAROON

BLUE

2.5

2.5 V A.C.

BLUE

BLACK

+90 V

RED

+ 240 V

GREEN

OUTPUT

RED

OUTPUT

TRANSFORMER

BROWN

+ 220 V

BLACK

+ L. S.F

- YELLOW

BLACK

-L S.F

GREEN

OUTPUT

BLUE

MAROON

RED

YELLO

BROWN

GREEN

4 80011

0.5 MR)

BLUE...

TERMINAL BOARD

including receiver assembly, socket power unit, and reproducer assembly

OUTPUT CHOKE

51511

FILTER

REACTORS UX 280

POWER

TRANSFORMER

120 V

[ 6 1 RECEIVING LOUD LOCAL STATIONS

If excess volume control adjustment is used on local stations the signal will

apparently

have two peaks on the tuning dial. A further advance of the volume control

will decrease

the volume abruptly rather than increase it.

This is entirely normal, and is caused by tube

overloading. The correct method of tuning this receiver on local stations is to reduce

the

volume control to the position where the station will be received at only one position on

the

station selector dial, and then adjust the volume control for the desired volume.

On some stations when tuned in with excessive volume, distortion may be experienced.

The remedy is to reduce the volume control until the distortion disappears.

The "Local -

Distant" switch serves a distinct purpose here also.

See Part I, Section 8.

If a steady whistle occurs with a powerful local (not a heterodyne between two stations

which is a natural condition and impossible to eliminate), it can usually be eliminated or

reduced by slightly detuning the station selector.

Interference from long wave stations is

eliminated in most cases by the new antenna semi -tuned inductance.

110 V.

TAP

105-125 VOLTS

50.60 ti A. C.

o -

OPERATING

SWITCH

Page 12

This tuning procedure should be explained to the owner when an installation is made.

[ 7

ADJUSTMENT FOR LOW LINE VOLTAGES

A lead is provided under the S.P.U. for use when the No. 600 receiver is connected to

lines, the voltage of which never exceeds

115

volts. A good plan is to allow the lead to

remain as connected in manufacture unless unsatisfactory operation is experienced. Should

it be determined by measuring the line voltage at intervals with a good A.C. voltmeter (as

incorporated in Weston Test Set No.

537)

that the line voltage never exceeds

115

volts

adjustment may be made as follows:

(a) Remove S.P.U. as described in Part IV, Section

15.

(b) Connected to the operating switch will be found two soldered connections, one of

which has a transformer lead (black with red tracer), connected to the switch.

Unsolder this connection and tape up the transformer lead so that it will not ground

or short to other parts.

lead.

Clean the end for soldering and solder this lead to the switch connection from

which the black with red tracer transformer lead has been removed.

(d) Replace S.P.U. in reverse manner.

The 110 -volt tap of the transformer is now properly connected and the receiver may be

used on

105-115

volt lines with maximum efficiency.

Figure 25

illustrates the changes to

be made.

PERFORATED SCALE

DIAL SCREEN

AND SUPPORT

APERTURE''

PILOT LAMP

- BRACKET

SUPPORT BRACKET MOUNTED

ON GANG CONDENSER ASSEMBLY

(ASSEMBLY NOT SHOWN)

Figure 7-Dial

screen, tuning scale and pilot lamp

[ 8 ] "LOCAL -DISTANT" SWITCH

The "Local -Distant" switch is an antenna switch, which disconnects the antenna from the receiver when in the local position. When closed it permits distant reception due to the proper normal antenna connection.

The purpose of .this switch is to prevent the strong

carrier of a powerful local station from overloading the tubes, thereby causing distortion and

also permit better radio frequency selectivity for local stations close to each other in kilocycle

assignment. Keep the switch, as a general rule, at the local position unless sufficient pick-up

is not obtained, when the switch may be thrown to the distant position.

[ 9 ] JERKY ACTION OF STATION SELECTOR

Should operation of the station selector be stiff or jerky a little oil dropped on each

condenser bearing will effectively remedy this condition. When experiencing this trouble it

is also well to check the cable tension spring to make sure that suitable tension is being

applied to the condenser drive cable.

[ 10

INSTALLATION OF PILOT LAMP

A projection type of dial lighted by a small concentrated filament lamp is used in this

receiver.

The lamp is mounted so that its rays pass through the pierced scale of the dial

and then project the scale divisions on an amber window on the front of the cabinet.

It is

therefore important to mount the lamp so that its rays will pass through the correct

open-

ings to fully illuminate the scale readings on the window. Figure

shows the general arrange-

ment of the pilot lamp and dial.

Page 13

To install the pilot lamp proceed as follows :

Turn the station selector counter -clockwise to its extreme position so

that the pilot

lamp mounting will be accessible. Remove the socket clamp from its bracket and screw

the

lamp firmly into the socket.

Replace the socket clamp on its bracket.

Now turn the power "On" at the operating switch.

With the station selector in the

extreme counter clockwise position adjust the socket clamp on its

brackets until the zero

mark on the scale projected on the dial screen is about Y4. inch below the index

pointer.

To replace a bulb, pull the socket back from its position and remove the old bulb.

Place

the new one in the socket and screw in tightly.

The socket is then pushed down until the

front window is properly illuminated. There may be a slight variation in the centering

of the

filaments of various lamps which might tend to throw the light too much to one side

of the

window.

If this happens pull the socket out and bend the metal arm that holds the

socket

to one side until the rays of the lamp properly illuminate the scale

window. Now tune in

a station, the dial setting of which is known.

If the dial setting for the station tuned in

is different from that formerly obtained pull the lamp back or push it forward until the dial

reads the same as that previously obtained for that station. The lamp itself may be out

focus due to excessive or too little solder on the base tip connection. This can be remedied

by replacing the lamp with the spare provided, or by taking away a little solder with a

hot

soldering iron.

LOW IMPEDANCE INPUT TRANSFORMER

TO RADIOLA 66

PHONCOGRAPHUP

(1:60 RATIO APPROX.)

2e (PWR.) DET.

VOLUME CONTROL

SINGLE POLE

POTENTIOMETER

DOUBLE THROW

6011

SWITCH

1 3

,00011

Figure 8-Schematic circuit diagram of phonograph pick-up connections

[ 11 ] PHONOGRAPH PICK-UP

Connecting lugs for a phonograph, pick-up are provided and are shown specifically in

the schematic diagram Figure 6.

The proper arrangement of parts and conneotions' for a

low impedance type pick-up are schematically shown in Figure 8.

If a high impedance type

pick-up is used, as is most generally found in the open market, the 1 to 60 step up input trans-

former as shown in Figure 8 should be changed to a 1 :3 input transformer as recommended

by the individual manufacturer. The volume control potentiometer should also be changed to

that recommended by the manufacturer.

It is important to have the resistor connected as

shown to the single -pole double -throw switch for changing over from the audio amplifying

system for phonograph operation (close switch from contact 2 to contact 3), to

that of radio

reception (close switch from contact 2 to contact 1). Contacts and switch arrangements, as

well as the necessary 2000-ohm'resistor, are shown in Figure 8. For phonograph

operation the

receiver volume control should be at extreme minimum setting as well as "Local

-Distant"

switch in "Local" position.

If a high pitched audio frequency whistle occurs with some

types of phonograph pick-ups it is advisable to ground the lower end

of the primary of the

input transformer (end closest to letter P of diagram shown above) and

pick-up sus-

pension arm.

[ 12 ] LOCATION OF RECEIVER IN ROOM

As with other musical instruments, the location of the receiver in the room should be

chosen with care. Various positions should be tried until the most desirable

reproduction is

obtained.

If this position is outside the radius of the connection cord to the A.C. outlet,

an extension cord can be used.

[ 13

KNOBS

The No. 600 receiver uses an improved type of push knob on'the station selector

and

volume control shafts. This knob is removed by simply pulling it off the shaft, and

replaced

by pushing it on. Very little trouble should be experienced, as no set screws or

other parts

that might give trouble are used.

Spacers are provided on the shaft to keep the knobs at

proper distance from the receiver front, and if removed, should

be carefully replaced.

Page 14

PART II-SERVICE DATA

[ 1 ] ANTENNA SYSTEM FAILURES

A grating noise may be caused by poor lead-in connection to the antenna;

or the

antenna touching some metallic surface, such as the edge of a tin roof, drain pipe, etc.

disconnecting the antenna and ground leads the service man

can soon determine whether the

cause of complaint is within or external to the receiver and plan his service work accordingly.

[ 2

RADIOTRON SOCKETS

The sockets used in the No. 600 receiver are

a six -gang UY socket assembly and two

single UX sockets. One of the UX sockets is used in the socket

power unit and is of the

same design as that used in the receiver assembly.

The bakelite Radiotron guide shields used in the receiver assembly will prevent

any pos-

sible shock from contact with high voltages in the socket when inserting the Radiotrons.

Figure 9-Drive cord assembly for gang tuning condensers

The prongs of the tubes fit into this shield opening

very snugly and require only a twist until

the prongs find the correct holes into which they fit. This is especially helpful when inserting

the five -prong tubes into their sockets.

[ 3 ] RADIOTRON PRONGS

Dirty Radiotron prongs may cause noisy operation

or change the resistance of the fila-

ment circuits sufficiently to cause a hum in the loudspeaker.

They should therefore be

cleaned with fine sandpaper periodically to insure good contact. The

use of emery cloth or

steel wool is not recommended.

Before re-inserting the Radiotrons in their sockets wipe

the prongs and base carefully to make certain that all particles of sand

are removed.

If a Radiotron will not fit into a socket without considerable

pressure, look for excessive

solder on one or more of the prongs. Excessive solder

on the prongs may be removed with

a file or knife.

r 4

LOOSE VOLUME CONTROL

A loose volume control arm may cause noisy or intermittent operation.

It should be

bent slightly so that it makes firm contact against the resistance strip.

To do this it

necessary to remove the chassis from the cabinet as described in Part IV, Section 1.

The

volume control is then accessible.

It can be released by removing the two screws that hold

it to the metal frame, after unsoldering connections to its three terminals.

[ 5 ] BROKEN CONDENSER DRIVE CORD

The main tuning condensers are controlled by the station selector knob, the motion of

which is transmitted by means of a rugged fish line to the drum

on the end of the tuning

condensers. Should this cord become broken, and a new

one not be available, a temporary

repair may be made by tying the two ends together by

means of a square knot and then

replacing the cord in its correct position as shown in Figure 9. The shortening caused by the

Page 15

knot can be compensated for by untying the knot at the tension spring end and using a part

of the spare length. The tying of the knot at the ends of the cord should be the last opera-

tion, because the correct amount of tension can then be obtained at the tension spring.

Fig-

ure 9 shows the arrangement of the drive cord over the drums.

This should be followed

when replacing the cord.

See Part IV, Section 5.

[ 6 ] RADIOTRONS FAIL TO LIGHT WHEN OPERATING

SWITCH IS "ON"

Should all Radiotrons fail to light when the operating switch is "ON", look for :

(a) House current switched off; loose connection at convenience outlet; or open A.C.

input leads.

(b) A.C. input plug to S.P.U. not in position.

(d) Lane voltage tap not connected.

(e) Damaged power transformer in S.P.U.

(f) Burned -out filaments in Radiotrons not lighting.

The remedy for (a), (b), (c), (d), and (f) is apparent. Any external cause, such as

D.C. supply, etc., of (e) should be located and eliminated before making replacements.

BAKELITENN

,STEEL BLADE

Figure 10-Dimensions of the

non-metallic screw driver

Figure 11-Method of adjusting compensating and

oscillator trimming condensers in cabinet

[ 7

PLATES OF RADIOTRON UX-280 EXCESSIVELY HOT

Should the plates of Radiotron UX-280 become excessively hot, check the following:

(a) Shorted 2 mfd. filter condenser on high voltage side of filter reactor.

(b) Internal short in power transformer. Test for grounds to shield or to core,

or short

from one winding to another.

[ 8 ] NO SIGNAL-RADIOTRONS O.K.

If the Radiotrons appear to be functioning properly and no signals are heard from the

loudspeaker with the volume control at maximum, check the following:

(a) Inoperative Radiotrons.

Defects other than filament failure are not apparent until

the tubes are tested.

Inoperative Radiotron UX-280 may cause low voltages at the

terminal strip, or at the Radiotron sockets.

(See Part III, Sections 2 and 3, for

voltage readings.)

(b) Antenna grounded or shielded, or some defectively grounded part.

Check receiver wiring by in-

spection for poorly soldered joints, or grounds due to excessive soldering.

Then

resort to continuity tests and ground tests as outlined in Part III, Sections 5 and 9,

to determine defective wiring, or open connections.

(d) Loose connections at S.P.U. terminal strip.

(e) Open movable coil on cone or defective output transformer on reproducer frame.

(See Part III, Section 7.)

(f) Defective S.P.U. Check by means of continuity test.

(g) Open field coil in reproducer unit.

Page 16

[ 9 ] HUM

If a pronounced hum develops during operation check the following:

(a) Low emission Radiotron UX-280. A low emission rectifying tube will cause exces-

sive hum and unsatisfactory operation.

(b) Defective center tapped resistance. A short or open of this resistance will cause

a loud hum and imperfect operation of the receiver.

resistances may cause a certain amount of hum.

These defects will have a pro-

nounced effect on the general operation which will be more noticeable than the

additional hum.

Check by means of the continuity test given in Part III, Sec-

tions 5 and 6.

(d) An open filter condenser in the S.P.U. may cause a hum.

Check by testing con-

densers as outlined in Part III, Section 8.

(e) Shorted filter reactor will cause excessive hum. Check by resistance test.

Part III,

Section 6.

(f) A.C. induction may cause hum due to misplaced leads.

(g) Open by-pass condensers may cause excessive hum.

A mechanical hum caused by vibration of loose laminations in the power transformer

may be corrected by removing the power transformer from the S.P.U. as

described in Part

IV, Section 16, and heating it in a slow oven.

The open end should be kept up and the

compound heated sufficiently to allow it to adhere to the laminations of the transformer.

After heating, the transformer should be allowed to cool for at least 24 hours and then

returned to the S.P.U.

10 1 LOW VOLUME

Low volume may be caused by :

(a) Defective antenna system or defective "Local -Distant" switch when in "Distant"

position. A poor antenna and ground in a shielded locality may cause weak signals.

The suggestions given in Part I, Sections 1, 2, 3 and 4, should be followed if

trouble of this kind is experienced.

(b) Defective Radiotrons. A defective Radiotron in any stage may cause weak signals.

Before checking other causes it is a good plan to check all Radiotrons by interchang-

ing them with ones of a similar type known to be in good operating condition.

If this condenser is badly out

of adjustment it will have the effect of making the receiver very insensitive.

adjust correctly refer to Part II, Section 14.

Open or shorted plate winding will

prevent regeneration.

Refer to continuity tests, Part III, Sections 4 and 5.

(d) Oscillator trimming condensers out of adjustment.

Should the oscillator trimming

condensers be out of adjustment the receiver may be sensitive at certain portions of

the tuning scale and very insensitive at other sections.

Also two tuning points may

be found for the same station.

Should these condensers be badly out of adjust-

ment, only very loud local stations will be heard.

The correct method for adjust-

ment of these condensers is given in Part II, Section 17.

(e) Intermediate transformers not correctly tuned or matched or in themselves de-

fective.

Should the tuning condensers connected across the secondaries of the

intermediate transformers be out of adjustment, weak signals and poor tuning or,

in some cases no signals will result.

Refer to Part II, Section 16, for the correct

method of adjusting the I.F. transformers.

(f) Defective A.F. transformer.

Check by means of the continuity test (also Part II,

Section 19) and make any replacement that is necessary.

(See Part IV, Section 7.)

(g) Low voltage from S.P.U. Check voltages at terminal strip or sockets with readings

given in Part III, Sections 2 and 3. Low voltages may be caused by a low emission rectifying tube or defective resistances in the S.P.U. or receiver.

Check by means

of continuity test.

(h) Open, short or ground of various connections in receiver.

Check by means of con-

tinuity tests or ground tests and make any repair or replacement that is necessary.

Page 17

[ 11 AUDIO HOWL

Audio howl may be caused by :

(a) Incorrect adjustment of the R.F. compensating condenser. A compensating con-

denser adjusted to the verge of oscillation may cause a howl on nearby stations.

Adjust as suggested in Part II, Section 14.

Faint beat notes heard when listening

to loud stations on frequencies of 875 and 700 are not due to incorrect adjustment,

and may be usually avoided by slight detuning until the beat disappears.

(b) A howl may be caused by natural heterodyning of two stations close in frequency.

Distortion will also be produced.

This, of course, is no fault of the receiver.

An open of the A.F. condenser may cause a

howl.

(d) Open by-pass condenser connections.

An open of the connections to the by-pass

condensers may cause a howl.

(e) Defective volume control resistance.

Should there be an open or short in the

volume control or in its adjacent resistances an audio howl may develop.

Figure 12-175 K.C. test oscillator

(f)

175 K.C. and 180 K.C. TEST

OSCILLATORS

The General Radio Co. of Cambridge, Mass.,

can supply the new 175 K.C. Test Oscillator as

illustrated.

This oscillator, Type

360, has

output meter that may be connected directly to

the output terminals in

the No. 600 reee:ver.

The broadcast band oscillator completely covers

the range of 550-1500 K.C. by means of a cali-

brated variable condenser. A pilot lamp

is in-

corporated in the set and all necessary leads and

tools are supplied.

The General Radio Co. will undertake to add

the necessary parts to the 180 K.C. Test Oscil-

lator, Type 320, that any distributors have used

for service on the Graybar Super -heterodyne sets,

to provide for the 175 K.C. drive which is nec-

essary with the No. 600. Type 320, 180 K.C.

Test Oscillator should be forwarded to the Gen-

eral Radio Co. to have these changes made at a

nominal cost.

Vibrating elements in receiver Radiotrons. A gradually developed howl may be

due to the loudspeaker causing the receiver Ra,diotron elements to vibrate. Check

as described in Part II, Section 12.

(g) Poorly soldered or corroded joints.

Any high resistance joint throughout the

receiver may cause a howl.

(h) Defective resistance in S.P.U. or the receiver assembly. An open resistance unit

may cause howl.

Under such conditions it is advisable to turn the set "off" until

the trouble is found, otherwise excessive voltage rise may cause further damage.

(i)

Neutralizing condensers in intermediate transformers out of adjustment.

This may

cause oscillation in the I.F. stages which can be conveniently determined by remov-

ing Radiotron No. 1 and listening for the familiar oscillation sound when tuned to

a loud local station with volume control at maximum setting.

This I.F. oscillation

will result in a howl when a station is tuned in, especially at loud volume.

Adjust

the neutralizing condensers as described in Part II, Section 16.

(j) Open of any of the several ground leads in the receiver.

This may cause some of

the circuits to go into oscillation and result in a howl when a station is tuned "in".

Generally a loud hum will also be present.

The several grounding leads in the

Receiver Assembly and in the Socket Power Unit should be checked and

any open

or poorly soldered joint should be repaired.

(k) Pilot lamp socket being grounded may cause a howl or excessive hum.

[ 12 ] ACOUSTIC HOWL

Acoustic howl is caused by vibration of the elements in the receiver Radiotrons.

This is

amplified in the reproducer unit.

Conditions being favorable the howl

may increase in

intensity and drown out the broadcast signal.

Page 18

The No. 600 receiver assembly, after the shipping blocks are removed, is mounted on rubber cushions to prevent any microphonic action.

Should trouble of this kind be ex-

perienced, examine the rubber cushions in the cushion brackets to make

sure the receiver

assembly is fully resting on rubber.

If this is O.K. the Radiotrons in the receiver should be

interchanged until the howl is eliminated.

[ 13 ] DISTORTION IN REPRODUCER UNIT ONLY

Distortion in the reproducer unit may be due to any of the following causes:

(a) Cone out of alignment.

Refer to Part II, Section 22.

(b) Leads from cone coil broken away from side of cone. Make these leads fast with

a little shellac.

Any loose part in the cabinet

will cause a rattle.

Tighten all loose parts.

(d) Foreign material in core space.

(e) Defective output transformer. Check continuity and resistance, Part II, Section 21.

[ 14 ] ADJUSTMENT OF R.F. COMPENSATING CONDENSER

The radio frequency compensating condenser should not be touched unless it is definitely

ascertained that no other failure exists as a possible cause of receiver insensitivity, which is

the most noticeable indication of the need for adjusting, providing different tubes have been

tried as pointed out in Part I, Section 5.

An oscillating condition of the receiver may be caused by improper adjustment of this

condenser.

A step by step procedure for making proper adjustment follows:

(a) Produre a long, thin, non-metallic screwdriver (See Figure 10). (b) Place receiver in operation in usual manner and tune in a weak station, preferably

at the middle or upper wavelengths.

If only a loud signal is available, place

"Local -Distant" switch in "Local" position.

(d) With the volume control at the position of maximum setting adjust the screw of

the condenser until the receiver goes into oscillation.

This will cause a whistle

whenever a station is tuned "in."

Then turn the screw in the opposite direction

until the set just goes out of oscillation and no howl is experienced when receiving

loud local stations. Now tune in stations throughout the range of the receiver and

note whether oscillations occur.

If they do, it will be necessary to reduce the

setting slightly. This is the correct adjustment for the radio frequency compensat-

ing condenser.

[ 15

DISTORTED REPRODUCTION CAUSED BY OTHER

THAN REPRODUCER UNIT

Under normal conditions the No. 600 receiver will deliver a strong signal of excellent

quality to the loudspeaker.

The high sensitivity makes it undesirable to operate the set

at full volume when receiving from nearby broadcasting stations.

if the normal reproduc-

tion is poor, test the output from the receiver. A pair of phones may be used for this pur-

pose.

Poor quality or distortion may be due to any of the following causes, other than

natural over -loading as explained in Part I, Section 6:

(a) Defective Radiotrons.

Though the receiver may be in operating condition a de-

fective Radiotron in any stage will cause distortion.

This is especially true of

the second detector, audio stage and the rectifier tube.

(b) High or low plate and grid voltages from the Socket Power Unit or a defective

resistor in the Receiver Assembly.

In the Socket Power Unit distortion may be

caused by a defective Radiotron UX-280 or resistance unit.

See Part II, Section 19.

Check by means of con-

tinuity test and replace if necessary.

(d) Trimming condensers out of adjustment.

Should the oscillator trimming con-

densers be out of adjustment the beat signal may not be exactly the frequency to

which the intermediates are tuned.

This will cause weak signals and distortion of

those received.

This condition may or may not be present throughout the tuning

range of the receiver.

Adjust as described in Part II, Section 17.

Page 19

(e) Receiver oscillation.

Should some circuit other than the oscillator be oscillating,

distortion will be experienced when tuning in a station.

This will be accompanied

by a whistle or squeal when the carrier wave of the station is tuned in.

To remedy

trouble of this kind see Part II, Section 11.

(f) Intermediate transformers out of line or not properly matched or in themselves

defective.

This will have the effect of giving distorted reproduction and reduce the

sensitivity of the receiver to a marked degree.

Line up the entire I.F. transformer

assembly as described in Part II, Section 16.

(g) Natural heterodyne between stations caused by being close in frequency.

This is,

of course, no fault of the receiver.

(h) Open by-pass condensers may cause distortion.

Check larger ones by method out-

lined in Part III, Section 8.

Smaller capacities should be replaced, if suspected,

unless a capacity bridge is available.

(i) Defective connections.

Check by continuity and ground tests as outlined in Part

III, Sections 5, 6 and 9.

Figure 13-Method of adjusting I.F. tuning condensers

and neutralizing condensers

While this and other adjustments may be made with the receiver chassis in

the cabinet, better accessibility is obtained by removal from the cabinet.

16 1 ADJUSTMENT OF I.F. TRANSFORMERS

The three I.F. transformers used are of the air core, tuned primary and tuned sec-

ondary type.

The primary condenser is of the fixed type, while the secondary

is adjustable.

Also in I.F. transformers No. 1 and No. 2 an adjustable condenser is provided

for neutral-

izing the I.F. stage. Figure 23 illustrates the internal connections of all the I.F.

transformers.

Should a transformer burn out or its primary fixed condenser change in

capacity it will

be necessary to replace that particular transformer. The correct procedure for

making such a

replacement is contained in Part IV, Section 10.

A simple method of locating a shorted transformer is to use a resistance

bridge or the

resistance measuring method described in Part III, Section 7.

The approximate transformer

primary D.C. resistance is 20 ohms ; secondary 100 ohms.

Due to the circuit

rrangement

(See Figure 6) it will only be possible to get a reading of

50 ohms on the secorldary as the

end connection goes to the neutralizing condenser and the reading must

be made at the cen-

ter tap connection.

This condition is true only of I.F. transformers No. 1 and No. 2.

I.F.

transformer No. 3 has no center tap in its secondary, and

therefore can be measured for

the full secondary resistance of approximately 100 ohms.

After replacing a defective I.F. transformer, or to make adjustments, the

following tun-

ing and neutralizing procedure must be followed for correctly

lining up the various circuits.

This is of utmost importance, as the entire performance

is based on the correct functioning

of intermediate stages.

Page 20

The following equipment is needed:

1. A Test Oscillator (Driver).

See Figure 12.

2. A coupling lead for coupling the output of the Driver to the grid or stator of the

first detector gang condenser (See Figure 13).

3. A non-metallic screw -driver.

4. A "dummy" Radiotron UY-227-A normal tube with one heater prong removed. Preliminary steps to be taken before adjusting the tuning, neutralizing and trimming

condensers:

(a) Remove receiver assembly as described in Part IV, Section 1, but leave all connect-

ing lugs connected to the S.P.U. terminal strip (the terminal strip cover and insu-

lator should be removed).

Place the receiver in the position shown in Figure 13.

(b) Disconnect red leads from output transformer to cone coil binding posts (See Fig-

ure 22).

To these should be clipped the meter terminal leads as shown in Figure

13.

If it is desired to tune to resonance by ear as well as by sight of the meter

(the latter, of course, should be used at all times for accurate settings), do not

disconnect the red leads, but clip the meter leads to the cone coil binding posts on

the loudspeaker frame.

The switch under the meter of the "Driver" should be

thrown to the dynamic ("Dyn") position.

If a General Radio 180 K.C. "Test

Driver," altered for 175 K.C., is used, the brown lead from the receiver should be released from Terminal No. 6 and the 0-2 D.C. milliammeter of the "Test Driver" inserted in series with correct polarities.

If a separate meter is used a 0-5 D.C.

milliammeter should be used, or a 0-2 D.C. milliammeter with 15,000 ohms in series.

oscillator gang condenser assembly.

This places the output of the "Driver" into the

I.F. stages through the first detector (See Figure 13).

This connection is recom-

mended for neutralizing with phones, as will be explained later.

For the tuning

procedure if too much pick-up is obtained the lead with the coupling coil should

be placed under the center coil of the R.F. and oscillator assembly.

(d) Replace all Radiotrons except the oscillator, No. 5, and turn operating switch "On."

(e) Place "Driver" in operation by switching "On," and set switches and vernier

condenser at 175 K.C.

The note from the driver will then be heard in the loud-

speaker if connected.

The I.F. transformer tuning condensers may now be adjusted as follows:

(f) Adjust the tuning condensers successively on the first, second and third I.F. trans-

formers (Figure 14), for maximum signal in the loudspeaker and maximum read-

ing on the milliammeter.

If pointer should go off milliammeter scale reduce the

volume control.

After making one adjustment on the transformers it is

a good plan

to repeat, as slight changes may have occurred in tuning the other circuits.

signal, or a loud howl, indicates neutralizing condensers

are out of adjustment and

they should be readjusted.

If meter swings abruptly off scale it is usually a good

indication that the I.F. stages are in an oscillating condition.

No further tuning

should be attempted until the I.F. stages are correctly neutralized. A maximum

reading, without the last mentioned condition, indicates correct tuning of the inter-

mediate stages.

It is now necessary to check the neutralization of the I.F. stages

as follows:

(g) Leave all adjustments and apparatus in position

on completion of tuning, but sub-

stitute a pair of phones for the loudspeaker by disconnecting the red leads (black

meter leads of "Driver" also),

and connect the phone tips to these terminals by

clip or handy fastener for a good temporary connection.

If greater response is de-

sirsd in the phones, they may be connected to the green (See Figure 22),

output

tratisformer leads when removed from their binding posts.

This connection is not

generally satisfactory, as the A.C. hum for phones at this point is rather-

high to

determine a good minimum neutralizing point.

This connection may also be used

for the meter of the "Driver" in the tuning procedure, with meter switch

thrown

to magnetic speaker position ("Mag"). Proceed then by placing the dummy Radio-

tron in first I.F. socket.

Now adjust the neutralizing condenser on the first I.F.

transformer for the position of minimum or no signal.

This is easily identified and

the adjustment is not critical.

(h) Replace the first I.F. tube and place "dummy" tube in second I.F. stage and

adjust

Page 21

the neutralizing condenser on the second I.F. transformer for position of minimum or no signal as described in the preceding paragraph (g).

Figure 23 illustrates the

internal connections of the I.F. transformers.

The third transformer does not

require neutralizing.

(i)

It is good policy to re -check the tuning of the I.F. transformer stages after neu-

tralization.

See paragraph (f).

After the I.F. transformers are properly tuned and neutralized they should perform

at their maximum efficiency.

It is a good plan to check the adjustments of the two oscillator

trimming condensers (See Figure 11) at this point.

The correct method for doing this

is indicated in Part II, Section 17.

Due to the increased sensitivity of the receiver it may be necessary to reduce the setting

of the R.F. compensating condenser to prevent the tuned R.F. stage from oscillating.

This

can be ascertained by tuning in stations of different wavelengths and

noting if the receiver

oscillates at any point throughout its tuning range.

(See Part II, Section 14.)

[ 17

ADJUSTMENT OF OSCILLATOR TRIMMING

CONDENSERS

Two trimming condensers are provided for adjusting the oscillator circuit so that the

beat note will always be 175 K.C. throughout the tuning range of the receiver.

Net I.F.

NEUTRALIZING CONDENSER

N2 1 I. F.

NEUTRALIZING CONDENSER

N23 I.F.

N22 I.F.

GANG CONDENSER

N21 I.F.

TUNING CONDENSER TUNING CONDENSER

ADJUSTING BUS

TUNING CONDENSER

Figure 14-Condenser adjusting screws for I.F. transformers

The most noticeable symptom of the oscillator trimming condensers being out of adjust-

ment is insensitivity in some sections or throughout the tuning range.

To check the adjust-

ment of the trimming condensers as a possible cause of any noticeable insensitivity in the

receiver proceed in the following manner, making sure the I.F. stages are in correct adjust-

ment (See Part II, Section 16).

(a) Procure the following equipment. A modulated oscillator giving signals at 1,400

and 600 Kilocycles.

The Test Oscillator shown in Figure 12 is suitable for this

purpose as it covers the broadcast band of frequencies 550-1,500 K.C.

A long thin non-metallic screwdriver.

Such a screwdriver is shown in Figure

10 with its dimensions.

With the test oscillator shown, the two red output leads of the receiver chassis

that normally go from the secondary of the output transformer to the cone coil

(See Figure 22) should be removed and connected to the output or meter terminals

of the oscillator with the clips provided and meter switch thrown to dynamic

("Dyn") position. If the test oscillator is not used, a 0-5 D.C. milliammeter or a

0-2 D.C. milliammeter with 15,000 ohms in series should be connected in series

with the brown lead that connects to lug No. 6 (See Figure 22) on the terminal

strip.

This places the meter in series with the plate supply of the second detector

and serves as a very good resonance indicator, as does also the other mentioned

method. The speaker cone coil may be connected at any or all the time if the connec-

tion assists in any way in tuning to the modulated output of the test oscillator.

Page 22

(b) Place in operation with receiver raised by blocks or

the rubber cushion supports

provided, in order to simulate the conditions when mounted

on the cabinet shelf.

Then place the oscillator in operation at 1,400 K.C., and with

the coupling lead

twisted around the antenna lead, tune by adjusting the station

selector until a

maximum deflection caused by the external oscillator is obtained in

the meter, or

resonance indicator.

Always adjust the volume control so that the deflection is

not

beyond the scale of the meter.

on the right, facing rear of the

receiver (Figure 15) with the long, thin, non-metallic screwdriver until

a maximum

deflection is obtained in the milliammeter.

The station selector should be moved

slightly as adjustment is being made in order to keep correct tuning

position, which

is indicated by maximum deflection.

(d) Adjust oscillator for 600 K.C. Tune in again carefully, but

now for 600 K.C. with

station selector and then adjust the trimming condenser

to the left for maximum

deflection of the milliammeter while tuning through signal.

(e) Now readjust at 1,400 K.C. as indicated in (b) and (c).

With this adjustment the trimming condensers

are correctly adjusted for

maximum efficiency, that is, so adjusted that the beat signal

will be 175 K.C.

throughout the tuning range.

(f) If the above fails to line up the trimming condensers,

bearing in mind that the

right trimmer is more critical than the left trimmer for usual

correct adjustment,

look for defective oscillator series condenser,

or defective oscillator coil assembly.

A two -peak effect of meter reading may be due to tuning through

a broadcast station

frequency that is being picked up.

If the speaker is connected this

can readily be

determined.

Figure 15-Method of adjusting oscillator trimming condensers

[ 18 ] TESTING ELECTRICAL ALIGNMENT OF

TUNING

CONDENSERS

The No. 600 receiver uses a three -gang tuning condenser,

one condenser being used for

the oscillator, one for the tuned radio frequency

stage and one for the heterodyne detector.

These condensers are accurately aligned electrically

at the factory and it

is important that

they maintain this electrical alignment.

Condensers not aligned will cause weak signals,

broad tuning and generally unsatisfactory operation.

The following procedure may be used

for checking and aligning the condensers properly.

(a) A small tool such as illustrated in Figure 17 is

necessary.

This may be easily

constructed from an old condenser plate,

a piece of wire and a Bakelite rod.

(b) Tune in a weak station or loud local with minimum volume

control setting at the

upper wavelengths.

Then with the condenser end of the tester, touch the

rotor

plates, see Figure 16, and note if an increase

or decrease of signal is obtained in

the loudspeaker.

Should touching the rotor plates and bring the plate closer

the stator plates increase the signal, then either that particular condenser

is low in

capacity or the coil it tunes is low in inductance.

Should the signal decrease in

volume, then the condenser and coil is either normal

or high in value.

Page 23

show the response, instead of broadcast signal as outlined in

(b), this may be

readily accomplished by connecting and using the Test Oscillator shown in Figure

12, and outlined in Part II, Section 17.

Decrease in signal strength by using the

tool mentioned above will be shown by a decrease in meter reading, after signal of

oscillator has been properly tuned in.

(d) After checking at the upper wavelengths, the procedure should be repeated at the

lower wavelengths.

To check against condensers or coils high in value the other end of the tester which has

the wire ring should be placed inside of the coils or near the end of the coil. This reduces

the inductance and should the coil be high in inductance or the condenser which tunes it

high in capacity, the signal will increase in volume.

By thus checking each condenser and the coil it tunes, a positive check on the electrical

alignment of the condensers and coils can be made.

Should a circuit be found that is high,

the end rotor plate of the particular condenser should be bent farther from the stator plates.

The correct amount can be determined by checking as previously described. If the oscillator

circuit should be out, a check must first be made of the adjustment of the trimming con-

densers.

See Part II, Section 17.

Should it not be possible to align the circuits by bending the plates or the gang con-

denser adjuster (See Figure 16), then the R.F. and oscillator coil assembly is not properly

matched.

In this case this assembly must be replaced as described in Part IV, Section 2.

Figure 16-Aligning gang tuning condensers Figure 17-Aligning tool

[ 19 ] AUDIO TRANSFORMER AND RECEIVER BY-PASS

CONDENSERS

Figure 20 shows the internal connection to external lugs of the single audio transformer

and by-pass condensers as well as the correct color coding of the external leads with their

correct internal connections.

(a) The transformer windings may be checked by the methods described in Part III,

Section 7.

The primary resistance is about 1,000 ohms.

The secondary resistance is about 5,200 ohms.

(b) The by-pass condensers may be checked by the method outlined in Part III, Section

8. Although this method does not give any knowledge as to the exact capacity, it is

a valuable, though rough, service check.

20 ] OUTPUT CONDENSER, OUTPUT CHOKE, AND FILTER

CONDENSERS

Figure 21 shows the internal connections to external lugs of the output condenser, out-

put choke, and filter condensers, together with their respective values.

These should be checked by the methods outlined in Part III, Sections 7 and 8.

Page 24

An open output condenser or an open or shorted choke will cause weak and distorted

reproduction. A defective filter condenser is indicated by excessively hot plates, possibly

showing color, in Radiotron UX-280.

Shorted output condenser will cause distortion.

[ 21 1 REPRODUCER UNIT

The No. 600 receiver uses a new type eight -inch dynamic reproducer rendering excellent

quality of reproduction.

The field coil is a high -voltage, low -current type, being supplied

from the UX-280 in the S.P.U.

This field is efficient in operation and marks a distinct ad-

vance in dynamic reproducer design.

A check on the continuity of the cone coiler field can be made by disconnecting them

from all other terminals and testing for continuity.

An open of either coil will indicate a

defect which must be remedied by replacing the entire cone or the field coil.

The output transformer also can be tested for continuity by applying methods

as outlined

in Part III, Sections 4 and 7.

The connections for the above parts of the reproducer assem-

bly are clearly shown in Figure 22.

Figure 18-Centering cone

Testing the resistance of the cone coil should show approximately 10 ohms for

normal

condition.

Similarly the output transformer primary resistance is 350 ohms, and secondary

is 16 ohms. The field coil drain is about 46 milliamperes at 300 volts D.C.

[ 22

CENTERING CONE OF REPRODUCER UNIT

To properly center a new cone or one out of center

use the following procedure:

(a) Remove reproducer unit from cabinet

as outlined in Part IV, Section 13.

(b) Loosen center screw of cone, but do not remove it.

a visiting card, 1Y2" x Y4." in

size, through the center web of the cone into the

space between the pole pieces and

the cone (Figure 18).

This will give the cone coil the same clearance

on all sides

of the pole piece.

(d) Tighten the center screw holding the web of the

cone and remove the three strips.

The cone is now properly centered.

(e) Replace reproducer unit in reverse order.

Page 25

PART III-ELECTRICAL TESTS

[ 1 ] VOLTAGE SUPPLY SYSTEM

Figure 19 shows the method of obtaining the plate, grid, cathode and heater voltages and

the high voltage field current from the main source.

However, in order to give the service

man a complete continuity picture of the voltage circuits it is not abridged, but drawn

actually

as it is found in the receiver, so that the tracing of voltages and currents

is actually done,

through the various component parts affected, as shown schematically in a straight line

manner.

By study of this schematic, the reason for no plate voltage on one I.F. socket with all

others O.K. is readily apparent, namely, the primary coil of the I.F. in question must be open.

A shorted primary condenser in an I.F. transformer means eliminating the resistance of the

primary coil.

These conditions as well as effects on voltages from shorted bias resistor con-

densers, etc., can be determined with study of this voltage supply schematic.

The correct

values of resistors, condensers, etc., are shown in the ordinary schematic diagram Figure 6.

+ 300 VOLTS D C.

OATS A C

'00000'

FILTER REACTOR

PLATE SERIES RESISTOR --_.r

TU ED

BLEEDER

RESISTOR,,

OLLIME

III

0_ (PM.)

DU.

-11-

cTEM,

CAMPO

TRANSFORmE

RIMARY'

A F.

FILAMENT

CENTER.TAPPED

RESISTOR

II ET

PHONOGRAPH

PICK-UP

TERMINALS

Uq2A5 BIAS

ESISTOR

Figure 19-Schematic circuit diagram of the voltage supply system

[ 2 ] VOLTAGE READINGS AT TERMINAL STRIP

Use D.C. voltmeter with a 0-300 volt scale and at least 1,000 ohms per scale volt such

as incorporated in Weston Model 537, Type 2, test set.

Line volts -120 A.C.-Tap at 120

volt connection.

Terminals

Volts

8 to 7

310

8 to 6

265

Terminals

Volts

8 to 5

275

8 to 4 120

Use a 0-5 volt A.C. voltmeter for the following reading:

Terminal 2 to 3, 2.7 volts A.C.

[ 3 ] VOLTAGE READINGS AT RADIOTRON SOCKETS

The following voltages

taken

at each

Radiotron socket with the receiver in

operating condition should prove

of value when checking with test

sets such as the Weston Model 537, Type 2,

or others giving similar

readings.

The plate currents shown are not necessarily accurate for each tube, as the cable in the test set will cause some circuits

oscillate, due to

its added capacity.

Small variations of voltages will be caused by different tubes and line voltages.

Therefore the following values must be taken as approximately

those that will be found under varying conditions.

The numbers in column

indicate the tube socket numbers shown in Figure 22.

VOLUME CONTROL AT ZERO

120 -Volt Line.

Tap at 120 -Volt Connection

Tube No.

Cathode

Heater

(D.C.)

Volts

Cathode or Filament to

Grid

(D.C.) Volts

-26

-20

-17

-9

-26

-20

-26

- 3

-16

-17

-29

-16*

Cathode or Filament to

Plate

(D.C.) Volts

Plate

(D.C.

Millam

-100

-95

-100

+100

+235

4225

1.6

7.3

8.7

0.7

31t

Filament

Or Heater

i (A.C.)

Volts

2.35

2.40

Page 26

VOLUME CONTROL AT MAXIMUM

120 -Volt Line.

Tap at 120 -Volt Connection

Tube No.

Cathode to

Heater

(D.C.) Volta

Cathode or Filament to

Grid

(D.C.) Volts

Cathode or Filament to

Plate

(D.C) Volts

Plate

(D.C.)

Millam_ps

Filament

or Heater

(A.C.) Volta

-24

-3.0

- 81

4.5

2.35

-17

-7.0

- 77

1.5

2.35

-24

-3.0

- 80

5.0

2.35

-24

-3.0

- 81

4.9

2.35

-16

6.6

2.35

-16

-29

-228

0.7

2.35

-16*

-225

30.51'

2.40

*The reading of 16 volts as herein found is correct.

Actually th's indicates a has voltage of about 44 volts on

the grid of the TJX-245. The actual lower reading is due to the

megohm (250,000 ohms) resistor naturally affect-

ing the scale of the voltmeter.

tThis reading

just off the scale

of the 0-30 milliammeter used in the Weston 537, Type 2, test set. The 0.150

M.A. scale should be used in case of readings in excess of 30.

\\:

\,\\

2 MFD.

0.5 roFD.

MFD.

1 MFD.

Figure 21-Internal connec-

tions of output choke, output

condenser and filter condensers

Figure 20-Internal connections of audio

transformer and by-pass condensers

METHODS FOR CONTINUITY TESTS

In making a continuity test whether it be for the complete receiver,

S.P.U., or individ-

ual parts, as the internal connections and windings of the A.F.

transformer shown in Figure

20, or checking the continuity of the I.F. transformers by

referring to Figure 23 for

schematic representation, the following procedure is recommended:

Disconnect the antenna and ground leads

; the cable connecting the socket power unit to

the receiver and loudspeaker, and the A.C. supply cord

at its outlet.

A pair of headphones with at least 4% volts in series,

or preferably a voltmeter with

sufficient voltage to give a full scale deflection when connected

across the battery terminals

should be used in making these tests, for example,

a 0-50 volt meter with a 45 volt "B" bat-

tery.

The receiver Radiotron socket contacts, numbers and

lugs used in these tests

are

shown in Figure 22.

The receiver continuity wiring diagram is illustrated

in Figure 23.

The S.P.U. terminal numbers are shown in Figures 6

and 24.

The voltage supply schematic

(Figure 19) will also be a help in studying continuity.

Test leads should be of the flexible insulated

type with partially insulated testing tips,

so that false readings will not be obtained through contact with the hands.

Similarly the

hands should not touch the chassis or component

parts.

The contacts of the test equipment should be placed

across the terminals or leads indi-

cated in the following test table under the column marked

"Terminals."

If the results are

negative the cause of such negative effect will be

found in the last column under the heading,

"Incorrect Effect Caused By." The second column indicates

the correct effect.

The third

column indicates the approximate correct resistance

in ohms of most of the circuits tested.

The R.F. and oscillator coil winding lugs

are coded (P) representing primary,' (S)

sec-

ondary, (S') secondary center -tapped, and (T) tertiary

or oscillator plate coil.

Refer to

Figure 23.

To test for grounded conditions refer to Part III,

Section 9.

Page 27

REPRODUCER

UNIT

TO FIELD COIL.

A.C. INPUT PLUG

STATION

SELECTOR.

LOCAL -

DISTANT

SWITCH

ANTENNA

GROUND

OUTPUT CHOKE,

OUTPUT CONDENSER

AND

FILTER CONDENSERS

--OUTPUT TRANSFORMER

GREEN

EI.LOW

TO CONE COIL

BLACK BLACK

FILTER

REACTORS

UX-280

SOCKET

SOCKET POWER UNIT

MAIN GANG TUNING

CONDENSER ASSEMBLY

AND DRIVE \

VOLUME

CONTROL

TE,DN.S,EDDRY.ER

bil

BY-PASS

CONDENSERS

SPLICES

OPERATING

SWITCH

CABLE-.

--CUSHION

MOUNTING

CBAR.

PHONOGRAPH PICK-UP

RECEIVER ASSEMBLY

TERMINAL STRIP

Figure 22-Cable connections, socket contacts, reproducer unit, socket

power unit and receiver assembly

Page 28

PHONOGRAPH PICK-UP

TERMINAL STRIP

TO OUTPUT

TRANSFORMER

(PRIMARY)

zany

an ec

au NJ ea

0 =

LA A-, A"

Z an an =

a--

oC a.

.:.ct

FILAMENT

CENTER

TAPPED --

RESISTOR

(60 11)

GROUND/

TO FRAME

UX-245

GRID .01

BIAS

RESISTOR

(1470.0

VOLUME CONTROL-,

MO XL)

A.F.TRANSFORMERs%N.....

SEC. SERIES RESISTOR F

Ar (VE MEGOHM)

SUS

BROWN

A.F

TRANSF.

SEC. COND.

4.°

NT 3 I.F TRANSF

A.F. TR AN SF.

PRI. RESISTOR

40,000.n. cos

R.E

BY-PASS

COND.

BLACK

.s 3401.F.

PRI. RESISTOR

(30 00 .H.)

BUS

TO STATOR

NOT I. F.)

- OF NO3

TRANSF.

,(GANG COND.(0SC)

OSCILLATOR

GRID LEAK

40,000

BLACK

I I

BLACKA

.A) B.LABCLKACK.i.e)

LLAC:LacK

I =.1

BLUE

I I

BLUE

BLACK

...AU)

OSCILLATOR

GR(I3D0R0E0SAIST)OR

tO4

;OSCILLATOR

/GRID CONDENSER

OSCILLATOR SERIES

FIXED CONDENSER

BUS

BLACK

SERIES OSCILLATOR

TRIMMING CONDENSER

PARALLEL OSCILLATOR

TRIMMING CONDENSER

BLACK

arena

m«rrrtrr rmmrnm

mir..1711.

TO STATOR

OF NE 2

GANG CORO

ID T.)

t' --VOLTAGE DIVIDING RESISTOR

BUS

YELLOW

..... BLEEDER

AND

- RESISTOR

feBLACKeAn, \

RED

(600011)

BLACK

TO ROTOR

OF GANG

COND.

GROUND CONNECTION

{

TO FRAME

PtK BLUE

/RACER

ACK

'NT I

I.F TRANSFORMER

TO STATOR OF Nt I

GANG CONDENSER (R.F.)

TO PILOT

FRAC

- LAMP

149

BLACK

BLAC

NeBLACKI

AABLACK.I

\Re BLACK)

BLACK

I I

BLACK./

R. F. AND OSCILLATOR

COIL ASSEMBLY

BUS

R. F. COMPENSATING

CONDENSER.

Figure 23-Continuity wiring diagram of receiver sub -chassis

EL ACK.e..../

Bus-)

GROUND

TO FRAME

TO GROUND

BINDING POST

LOCAL -

DISTANT

SWITCH

TO ANTENNA

BINDING POST

Page 29

[ 5

RECEIVER ASSEMBLY CONTINUITY TESTS

Remove all

Radiotrons and disconnect cable at terminal strip.

Remove all ground connections.

Remove pilot lamp.

See Figure

22 for cable lugs, terminals, and Radiotron socket contacts.

For convenience coloring of lugs as well as numbers are shown. Code-

Maroon (M), Black (Bla), Blue

(Blu), Red (R), Brown (Br), Yellow (Y), Green (G).

First-Inspect

all

connections to

observe any apparent faulty connection, rosin soldered joint, grounded or shorted lugs.

Any

connection removed or insulated as outlined below should be replaced before the next successive test.

Circuit

Antenna

Grid

Plate

Cathode

and

Filament

Misc.

Terminals

Correct

Effect

Antenna

post

ground

post

switch in "Distant" position.

GI to ground or Lug No.

(M)

G2 to Cl

G2 to ground

G3 to ground

G4 to Lug 8 (Y)

G4 to C4

[ Insulate

volume

control arm. See

LP. HI, S. 9.

G5 to C5

Insulate

volume

G5 to ground

{control arm. See

P. HI, S.

G6 to terminal A or Lug 8 (Y)

(Link closed)

G7 to Lug 8 (Y)

Closed Closed

Closed

Open Closed Closed Closed

Closed

(Weak)

Open

Closed

(Weak)

Insulate volume

P1 to ground

j control arm. See

L P. III, S. 9.

P1 to Lug 4 (Bla)

P2 to Lug 4 (Bla)

P3 to Lug 4 (Bla)

P6 to Lug 6 (Br)

P5 to 'Lug 4 (Bla)

P4 to Lug 4 (Bla)

Cathodes

1, 3

and 4

termi-

nal "C"

Cathodes

2, 5

and 6

Termi-

nal "C"

One filament

contact of Socket

7 to Lug 8 (Y)

Open

Closed

Closed Closed

Closed

Resistance

in ohms

(Approx.)

600

140

40000

If 3000

100

255,000

1050

1023

40000

Open

1.5

3000

Open

Incorrect Effect Caused by

Open antenna

inductance,

or open

"Local -

Distant" switch

Open secondary of

1st R.

F. transformer, or

open connection

Open secondary of 2nd R.

F. transformer, or

open connection

Shorted 0.5 mfd. condenser Open one-half secondary

1st I. F.

trans-

former

Open one-half secondary of 2nd

I. F. trans-

former or open volume control

Open one-half secondary of 2nd

I. F. trans-

former, or 90 -ohm portion of voltage dividing

resistor

Open grid leak or connection Shorted oscillator grid condenser

Open secondary of 3rd

transformer or

open connection

Open secondary of A. F. transformer, =4 meg-

ohm resistor, or connection

Shorted compensating condenser,

or grounded

1st detector primary, or connection

Open primary of 2nd R.

F. transformer or

connection

Open 1st

F. transformer primary coil,

connections

Open 2nd I.

F. transformer primary, or con-

nections

Normal

A. F. Primary condenser shorted

F. primary condenser shorted and primary

winding open

A. F. primary winding open

Open plate coil (Tertiary) of oscillator or con-

nections

Normal

Open primary

coil of 3rd

F. transformer

(Resistance 0. K.)

Shorted primary condenser

Open primary of

3rd I. F.

transformer and

resistor

Closed

Other filament contact of Socket

Closed

7 to Lug 8 (Y)

UNSOLDER ONE END

Lug 2 (Blu)

to one filament

contact Socket 7

Lug 3 (Blu)

to other filament Closed

contact Socket 7

Lug 2 (Blu) to one heater con-

Closed

tact of Sockets

1, 2, 3,

4, 5

and 6

Lug 3 (Blu)

to other

heater

Closed

contact of Sockets

1, 2,

3, 4,

5 and 6

OF FILAMENT

Closed

375

1500

CENTER

Open connection,

or 375 -ohm

section of the

voltage

dividing resistor.

If low resistance

then 0.5 mfd. condenser is shorted.

Open pick-up

winding of

oscillator

coil, or

connections

Open

one-half

of center tapped

resistor, or

UX-245 bias resistor, or

shorted condenser

(across biasing resistor)

if resistance is low

Open other half of center tapped resistor, or

UX-245 bias

resistor, or shorted condenser

(across biasing resistor)

if resistance is low

TAPPED RESISTOR

Open connections Open connections Open connections

G3 to P3

(Disconnect bleeder

resistor)

G4 to P4

(Disconnect bleeder

resistor)

G7 to output

transformer Lug

(G)

Terminal "C" to Lug 8 (Y)

(Open connection

between

vol-

ume control

and voltage

di-

viding resistor)

P6 to C6

C2 to C5

Lug No.

4 (Bla) to Terminal

Open

Closed

(Weak)

Open

Closed

257,000

6000

Open connections

Shorted 1st I.

F. neutralizing condenser

Shorted 2nd I. F. neutralizing condenser

Open resistors, or if closed strong, shorted 0.5

mfd. condenser

Shorted 0.5 mfd. condenser

Open oscillator pick-up coil

Open bleeder resistor

Page 30

'POWER TRANSFORMER CONNECTIONS

SPLICE--i..p4\

110 VOLT TAP

(TAPED LEAD)

UNDERWRITERS

KNOT

PLATE SERIES

RESISTOR

OUTPUT CHOKE.

OUTPUT CONDENSER

AND

FILTER CONDENSERS

YELLOW

REE

RUN

GROWN

ELLOW

UX-280

SOCKET

CABLE.:

+-SPLICES

FILTER REACTOR

CONNECTIONS

OPERATING SWITCH----

GROUND TO

FRAME

2..o

LILAC

TACK

Figure 24-Continuity wiring diagram of socket power unit

A. C. INPUT PLUS

SPLICES

[ 6

SOCKET POWER UNIT CONTINUITY TESTS

Remove Radiotron UX-280-Disconnect Cable at Terminal Strip.

Refer to Figure 24

TERMINAL'

STRIP

Terminals

Correct

Effect

Resistance

In ohms

(Approx.)

Incorrect Effect Caused by

G to P of UX-280 socket

Closed

240

Open high voltage winding of power transformer

Across filament

contacts

of UX-

280 socket

Closed -

Open UX-280 filament winding of power trans -

former

Terminal 2 (Blu) to

Closed

Open 2.5

volt filament winding

Terminal 3 (Blu)

Terminal 4 (M) to

Closed

4800

Open resistor

Terminal 6 (Y)

Terminal 5 (R) to Terminal 7 (Br)

Closed

735

Open output choke one

filter

reactor or con -

nections

Terminal 5 (R) to

Terminal 6 (Y)

Closed

1315

Open output choke, other

filter

reactor, or con -

nections

'Terminal 1 to ground

Closed

Open connection

Terminal 7 (Br) to

Open

Shorted one or more filter condensers

Terminal 8 (G)

Terminal 9 (Blu) to Open

Shorted output condenser

Terminal 5 (R)

Across A. C. input plug terminals

(operating switch on)

Closed

Open primary winding

power

transformer,

defective switch, or connection

Page 31

1 7 1 CHECKING RESISTANCE VALUES

The values of the various resistance units are shown in the schematic diagram, Figure

When testing a receiver for defects the various values of resistance should be checked.

This may be done by a resistance bridge; the voltmeter -ammeter method shown in previous

Service Notes ; or by the following method, the results depending upon the care exercised

in using the prescribed method.

For resistances of low value, 5000 ohms or less, use a voltmeter not greater than 100

ohms per volt.

The rating of 100 ohms per volt means that a meter with 50 volts maximum

scale reading, has a total resistance of 50 times 100, or 5000 ohms, when the 50 -volt scale is

used.

For high values of resistance use a meter of 1000 ohms or more per volt. The Weston

Meters, Type 301 and 280, each have a resistance of 62 ohms per volt and are satisfactory

for low values.

For very low resistances below 100 ohms, it is best to use a dry cell -1/

volt-with the 3 -volt scale of a Weston, Model 280.

For higher resistance up to 5000

and above use sufficient battery to give a good deflection on the meter, for example, a 45 -volt

"B" for a 0-50 unit meter.

Then take two readings, one of the battery alone, and one of

the battery with the unknown resistance in series.

Then apply the following formula:

Reading obtained

of battery alone

Resistance

Unknown

Reading obtained with

of meter

in ohms

Resistance

in ohms

resistance in series

Example-Using a Weston, Type 301, 30 -volt scale, 22Y, -volt "B" battery.

Resistance

of meter equals 30x62 or 1860 ohms.

(

22.5

8.45

)

1860 = 3091, or unknown resistance in ohms approx.

The above method may be used in checking the resistance values of the correct closed

circuits as shown in the Continuity Test Tables in Part III, Sections 5 and 6.

[ 8 ] TESTING BY-PASS CONDENSERS

Proper testing of the 2 mfd., 1

mfd., Y2 mfd., or 0.25 mfd. condensers is accomplished

by charging them with a handy D.C. voltage, as from "B" batteries connected to give 90 to

1.57y2 volts.

If sparking occurs as the charge is applied the condenser is shorted.

After

a few seconds wait, a strong spark (the strength of the spark being greater, of course,

for

the mfd. than the .25 mfd.), should appear when the condenser is discharged by shorting

the terminals with a screwdriver.

If no spark appears the condenser is probably open.

If a

slight spark occurs the condenser is probably leaky. A condenser having one side normally

grounded, as shown in the schematic Figure 6, and tested with the unit in the receiver, if

the opposite terminal is defectively grounded, the test will show a false short.

SmJaller by-pass condensers as used in the No. 600 receiver, in the order of .05 or

.0024 nifd. or less, cannot be successfully tested by the above method except for a shorted

condition.

For other suspected defects,

if unable to measure the capacity, simple trial

replacement is the best method.

[ 9 ] TESTING FOR GROUNDED PARTS IN RECEIVER

ASSEMBLY

Grounded parts may cause various effects, as weak signals or no signals, wrong or no

voltages at Radiotron sockets, etc.

The correct and necessary ground leads in the receiver are shown in Figure 6.

In testing for grounds that occur due to defective wiring or assembly, it is necessary to

remove all the correct grounding connections in order to discover the wrong grounded part.

This can readily be done by temporarily freeing the grounded leads to the frame as indicated

by the broken line the wiring diagram Figure 23, and insulating the rotating arm of the

volume control by slipping a bit of paper between the arm contact and the resistance strip.

Testing for a ground then may be accomplished by using the continuity testing methods

-preferably the method using a D.C. voltmeter with a battery in series. A defective ground

will be truly indicated by a closed continuity test between the frame (ground) and a terminal

of the suspected unit.

Page 32

PART IV-MAKING REPLACEMENTS

The various assemblies and parts of the receiver are readily accessible and replacements

can be easily made.

Figure 5 is a sub -chassis view of the receiver.

The following detailed

procedure outlines the simplest method to be used in making replacements:

[ 1 ] REPLACING THE VOLUME CONTROL

(a) Remove the knobs on the volume control and station selector.

These are of the

push type, and they are removed by simply pulling them off the shafts.

Between

each knob and the cabinet will be found a metal spacer.

These spacers must also

be removed. To replace, merely push the knob on to the shaft, first matching the

knob socket with its flat spring to the shaft, after replacing spacers.

OUTPUT

TRANSFORMER

OUTPUT TRANSFORMER

PRI. CONNECTING POSTS

OUTPUT TRANSFORMER

SEC. CONNECTING POSTS

TO CONE COIL LEADS

BAFFLE BOARD

Figure 25-Removing reproducer from cabinet

(h) Remove rear grill by removing the wing nuts holding it in place.

Then re-

move all cable connections to strip as well as connection to output transformer.

(d) Carefully remove the clamps that hold the cable and antenna wire to the side of the

cabinet.

(e) Remove the antenna and ground wires from their binding posts, and "Local

Distant" Switch.

(f) Pull cable, antenna and ground lead* from the shelf until all leads are c:ear.

(g) Remove the rear two screws and loosen the front two screws that hold the receiver

cushion supports to the shelf.

(h) The receiver assembly may now be lifted clear of the supports and removed from

the cabinet.

See Figure 26.

(i)

Place the volume control up and remove the two screws and nuts that hold it in

place. The soldered connections must also be removed from the three terminal lugs.

(j) Remove the old volume control and fasten the new one in position by means of the

two machine screws and nuts, and resolder the connections.

The correct connec-

tions of these leads are shoWn in Figure 23.

Page 33

(k) Return receiver assembly to cabinet and replace all cables and leads in the reverse

manner of that used to remove them and be sure receiver assembly rests on rubber

supports properly.

(1) Test receiver and if O.K. return shield and insulator to their original position.

[ 2 ] REPLACING R.F. TRANSFORMER AND OSCILLATOR

ASSEMBLY

The two radio frequency transformers and the oscillator coils are mounted on a metal

strip, together with three small adjustable condensers and two fixed condensers.

This assembly must be replaced as a unit-the matching of the coils being an important

point in the operation of the receiver. Use the following procedure :

(a) Remove receiver chassis from cabinet as described in Part IV, Section 1.

(b) Turn chassis on side and unsolder all leads to the assembly being replaced. (c) Remove the three machine screws and lock washers that hold the supporting strip

to the receiver frame.

(d) The assembly may now be removed and the new assembly fastened in position with

the three machine screws and washers previously removed.

(e) Resolder all connections in their correct position on the assembly.

This is shown

in Figure 23.

(f) The receiver assembly may now be returned to the cabinet in the reverse manner

of that used to remove it.

Figure 26-Removing receiver chassis from cabinet

[ 3 ] REPLACING RADIOTRON GANG SOCKETS

One socket assembly on the receiver chassis is of the gang variety, the other being a

single unit.

Both are held in place, together with their shields, by means of rivets which

clamp them on the metal chassis frame.

Use the following procedure when replacing these

sockets :

(a) Remove the receiver assembly from the cabinet as described in Part IV, Section 1.

(b) Unsolder all connections to the particular socket or assembly being removed. The

R.F. transformer assembly should be removed as a unit to provide room for replac-

ing the six -gang Radiotron sockets.

In the case of the

single UX or the gang UY the shield overlaps and will be held in place by the

socket not removed.

(d) Remove the old Radiotron socket and fasten the new one in position by means of

screws, nuts and washers.

Resolder all connections and replace the R.F. assembly

if removed. The correct connections are shown in Figure 23.

(e) Fasten receiver assembly in cabinet, connect cable and test.

If O.K., replace shield

over terminal strip.

Page 34

[ 4 ] REPLACING MAIN TUNING CONDENSERS AND

DRIVE

The main tuning condensers and drive

are replaced in one unit as follows :

(a) Remove receiver assembly from cabinet

as described in Part IV, Section 1.

(b) Remove pilot lamp and lead wires from condenser assembly.

Remove the three

screws, nuts and lock washers that hold the condenser assembly to the metal frame.

as far forward as possible and unsolder the four leads

connected at the rear. Remove the entire assembly by tilting slightly and pulling

clear.

(d) Place the new assembly in the position occupied by the old

one and solder the four

leads to their proper connections.

(e) Fasten the three screws, nuts and lock washers in their

proper position.

Make

sure that the screw that holds the ground connection on the under side of the

chassis makes firm contact.

Replace pilot lamp socket and lead wires.

(f) Return the receiver to the cabinet and replace all connections in the

reverse order

of that used to remove them.

[ 5 ] REPLACING CONDENSER DRIVE CORD

Considerable use may wear and break the condenser drive cord.

(a) To replace this cord it will be necessary to

remove the gang condenser assembly and

drive as explained in Part IV, Section 4.

(b) By following the diagram in Figure 9 tie the two ends of the

new cord together to

form a square knot; the finished looped length should be 103/4 inches

approximately.

rotor plates out) position

against the stop.

This position should not be allowed to change

or slip in the fol-

lowing procedure:

(d) Place cord with knot near the hole

on the drum, holding the cord with the fingers

of the left hand.

(e) By following the drive cord arrangements shown in Figure 9 the

cord may be

replaced. The cord should be started in the first

groove left of center on the drive

cord worm as viewed in Figure 9.

(f) When properly threaded, and with the drum still in its minimum position,

the

portion of the cord near the hole in the drum should be pulled through,

and caught

with the spring.

This will hold the cord in its proper tension.

(g) Rotate station selector to insure cord knot has been

set to run clear.

(h) Replace gang condenser and drive assembly in the

reverse manner removed.

[ 6 ] REPLACING R.F. COMPENSATING AND

OSCILLATOR

TRIMMING CONDENSERS

The R.F. compensating and oscillator trimming condensers

may require replacement.

The R.F. compensating condenser and the series oscillator

trimming condenser are identical,

electrically and mechanically, but the parallel oscillator trimming

condenser, located at the

right end when viewed from rear, is different electrically.

To replace use the following procedure:

(a) Unsolder connections from unit to be removed.

(b) Remove the two small machine screws, fiber washers and

nuts holding unit to R.F.

and Oscillator Coil Assembly metal support.

as shown in

Figure 23.

NOTE.-Care should be used in tightening the bolts holding the "Isolantite"

mounting, as uneven or excessive pressure may break the "Isolantite."

"Isolantite"

has very desirable electrical qualities and should be handled with

care to prevent

breakage.

Be sure to replace the fibre washers removed in (b) above.

Page 35

[ 7 ] REPLACING THE AUDIO TRANSFORMER AND BY-PASS

CONDENSERS

The No. 600 receiver employs one audio transformer and necessary by-pass condensers,

located at the left side of the receiver assembly facing the front.

Should a replacement

become necessary use the following procedure :

(a) Remove receiver assembly as described in Part IV, Section 1.

(b) Place the receiver chassis on its side and unsolder all connections to the audio

transformer and by-pass condenser leads and lugs.

The

new one is then fastened in position.

(d) Resolder the leads from the new transformer and by-pass condensers to their

correct points of connection as indicated in Figure 23.

(e) Fasten the receiver assembly in the cabinet in the reverse order of that used to

remove it.

CUSHION MOUNTING

FOR RECEIVER

BAFFLE BOARD

LOWER SUPPORT

Figure 27-Removing grill panel from cabinet

GRILL CLOTH

PROTECTOR

SCREEN

GRILL PANEL

[ 8 ] REPLACING PERFORATED DIAL SCALE

A step-by-step procedure to make replacement follows :

(a) Open rear grill.

(b) Turn dial so that the two screws that hold the dial in place are toward the rear.

(d) The old dial may now be pulled clear and the new one placed in the position occu-

pied by the old one.

Examine dial screen with pilot lamp lighted from the front

of the receiver to see that the numbers on the dial are in their correct position.

(e) Tighten screws holding dial in place after adjusting image correctly as outlined in

Part I, Section 10.

Replace rear grill.

[ 9 ] REPLACING POWER CABLE

A laced cable is used for connecting the S.P.U. to the receiver assembly and the

reproducer unit.

Should it be necessary to replace this cable use the following procedure :

Page 36

(a) Remove receiver assembly from cabinet as described in Part IV, Section 1.

(b) Turn assembly bottom side up and unsolder all connections to the cable.

all connections.

(d) Return assembly to cabinet in reverse order of that used to remove it.

[ 10 ] REPLACING INTERMEDIATE TRANSFORMERS

The No. 600 receiver has three intermediate frequency transformers.

No. 1 and No. 2

are similar mechanically and electrically, but No. 3 is different.

See Figure 23. These

transformers are mounted on "Isolantite" support board which has very desirable electrical

qualities and therefore should be protected against all damage as mentioned in Part IV,

Section 6.

A step-by-step replacement procedure follows:

(a) Remove receiver assembly from cabinet as described in Part IV, Section 1.

(b) Remove tuning condenser assembly as described in Part IV, Section 4.

Then turn up the

metal tabs on the upper side of the receiver chassis.

The old transformer may now

be replaced by the new one.

Turn over the metal tabs to hold it in place and re -

solder all connections. These are shown in Figure 23.

Be careful not to heat any

connection more than necessary to make a good joint, as excessive heat may change

the capacity of the primary fixed condenser, thus rendering the entire transformer

assembly defective.

(d) After returning the main tuning condensers to the receiver chassis in the reverse

order used in removal, it will be necessary to tune and neutralize the transformer

just connected in position.

The correct procedure for doing this is contained in

Part II, Section 16.

(e) The entire receiver may then be tested and a check made

on the adjustment of the

oscillator trimming condensers as described in Part II, Section 17., After all tests

and adjustments are completed the receiver assembly should be returned to the

cabinet in the reverse order of that used to remove it.

11 ] REPLACING TAPPED RESISTANCE UNIT IN RECEIVER

ASSEMBLY

A tapped resistance unit in the receiver assembly provides the various grid and cathode

voltages. To replace this tapped resistance unit proceed

as follows :

(a) Remove receiver assembly as described in Part IV, Section 1.

(b) Unsolder all connections to the tapped resistance unit.

This will release the unit and the new one can be fastened in place with the

screws,

nuts and washers previously removed.

(d) Solder all the leads to their correct connections.

(See Figure 23.)

(e) Return receiver assembly to cabinet in the

reverse order used to remove it.

[ 12 1 REPLACING MISCELLANEOUS PARTS IN RECEIVER

ASSEMBLY

The parts such as the UX-245 grid bias resistor, center tapped filament resistor,

oscil-

lator resistor, second detector plate to cathode by-pass condenser,

etc., may be easily removed

by unsoldering the connections of the parts themselves.

By observing the wiring diagram in Figure 23 and the photograph in Figure 5,

location

and wiring of any narticular part is readily ascertained for

purposes of removal and replace-

ment.

[ 13 ] REPLACING CONE OF REPRODUCER UNIT

To replace a cone, remove the entire reproducer unit from the cabinet, using

the follow-

ing procedure:

(a) Remove S.P.U. from upper shelf as outlined in Part IV, Section 15.

(b) Disconnect cable lead to output transformer primary.

same time

supporting the reproducer by hand to prevent it falling.

Place the unit in position

convenient for work.

Page 37

(d) Remove the nine nuts and machine screws that hold the cone ring in place.

Re-

move this ring and washers.

(e) Remove the screw and washer that centers the cone.

The cone may now be re-

moved and the new one placed in the position occupied by the old one.

(f) Return the centering screw, the ring, washers and nine scrOws and nuts to position,

but do not tighten.

The cone should now be centered as described in Part II,

Section 22, and all screws tightened.

(g) The unit should now be returned to the cabinet in the reverse manner of that

used to remove it.

[ 14 ] REPLACING OUTPUT TRANSFORMER

Should it be desirable to replace the output transformer, use the following procedure:

(a) Remove complete reproducer unit as outlined in Part IV, Section 13.

(b) Disconnect output transformer leads from their respective parts on the reproducer

frame.

unit will be free from the reproducer.

(d) Replace and connect in the reverse manner (See Figure 22).

[ 15

REPLACING FILTER CONDENSERS, OUTPUT

CONDENSER, AND OUTPUT CHOKE

The filter condensers, output condenser and output choke are enclosed as a unit in a

metal container.

Should replacement be necessary, use the following procedure:

(a) Remove the shield and all connections from the Socket Power Unit terminal strip.

(b) Remove the four machine screws that hold the S.P.U. to the cabinet.

The S.P.U.

may now be lifted clear of the cabinet.

Section 18.

(d) Unsolder all connections to the unit being replaced.

(e) Bend up the tabs that hold the unit to the S.P.U. base.

Remove the old unit and

fasten the new one in position by bending the tabs down so that it is held tightly to

the S.P.U.. base.

(f) Replace and solder all connections. The correct connections are shown in Figure 24.

(g) Return the S.P.U. to the cabinet in the reverse order of that used to remove it.

Replace all connections and test.

If O.K., replace shield over terminal strip.

[ 16 ] REPLACING POWER TRANSFORMER OR FILTER

REACTOR

The power transformer and filter reactors are both held in place by means of tabs which

form a part of their case, being turned over on the under side of the S.P.U. base. A step-

by-step replacement procedure follows :

(a) Remove S.P.U. from cabinet as described in Part IV, Section 15.

(b) To prevent damaging the series plate resistor remove it as described in Part IV,

Section 18.

(d) Bend up the tabs that hold the unit to the S.P.U. base.

(e) The old unit may now be removed and the new one placed in position.

Bend over

the tabs on the new one so that it is fastened tightly to the S.P.U. base.

(f) Solder all connections as shown in Figure 24.

(g) Fasten the S.P.U. in the cainet in the reverse order of that used to remove it.

Page 38

[ 17 ] REPLACING TERMINAL STRIP ON S.P.U. OR

RECEIVER

ASSEMBLY

Should the terminal strip on the S.P.U.

or phonograph pick-up terminal strip require

replacement use the following procedure:

(a) Remove the S.P.U. or receiver assembly from cabinet

as described in Part IV,

Section 1, and Section 15.

(b) Unsolder all leads to the terminal strip. (c) Release two screws holding strip to S.P.U. base,

or receiver assembly.

(d) The strip may now be removed and replaced by

a new one.

(e) Fasten new strip ir, position by

means of two machine screws, lock washers and

nuts previously removed.

(f) Solder all leads to terminal strip.

The color scheme and correct connections are

shown in Figures 23 and 24.

(g) Return S.P.U. or receiver assembly to cabinet in the

reverse order, and connect

cable properly (See Figure 22).

[ 18

REPLACING MISCELLANEOUS PARTS IN S.P.U.

The plate supply resistor and UX-280 socket

may require replacement.

The following

general outline will apply to these units :

(a) Remove S.P.U. from cabinet as described in Part IV, Section 15.

(b) Unsolder leads from defective unit.

nut and

lock washer holding the resistor to the brackets (riveted to S.P.U. base) by

threaded rod.

The UX-280 socket should be removed by drilling out the rivets and

replaced as is explained in Part IV, Section 3.

(.d) Solder leads to new unit as indicated in Figure 24.

(e) Return S.P.U. to cabinet in reverse order of that used to

remove it.

[ 19 ] REPLACING FRONT GRILL PANEL OR CLOTH

Should it be necessary to replace the front grill panel

or cloth the procedure below should

be followed :

(a) Remove S.P.U. as outlined in Part IV, Section 15. (b) Remove reproducer unit as outlined in Part IV, Section 13.

(d) Remove upper shelf by removing the wood

screws holding shelf to cabinet.

Save

screws and keep separate, as different length screws are used in this procedure.

(e) Remove reproducer baffle board by removing the wood

screws holding it in place.

(f) Remove lower baffle support (See Figure 27) by removing wood

screws holding

unit.

The front grill panel or board, which carries the grill cloth, grill cloth

protector,

and escutcheons, may now be removed after removing the wood

screws holding it in

place.

(h) New cloth may be replaced by using clamps

or tacks to hold it in place temporarily

while glue is applied to frame and the cloth lined up square and smoothed

out to

make a permanent job.

Replace front grill panel in reverse manner.

(g)

(i)

Page 39

SERVICE DATA CHART

Before using the following Service Data Chart, when experiencing no reception, low volume, poor

quality, noisy or intermittent reception, howling and fading, first look for defective tubes or a poor

antenna system. If imperfect operation is not due_ to these causes the "Service Data Chart" should be

consulted for further detailed causes. Reference to Part No. and Section No. in the "Service Notes" is also noted for further details.

Indication

Cause

Remedy

No Reception

Defective operating switch Loose volume control arm

Defective power cable

Defective R.F. transformer

Defective I.F. transformer Defective A.F. transformer

Defective Oscillator coil

Defective by-pass condensers

Defective socket power unit

Defective output transformer

Open cone coil of reproducer unit

Repair or replace switch

Tighten volume control arm, P. II, S. 4

Replace power cable, P. IV, S. 9

Replace R.F. and oscillator coil assembly, P. IV,

Replace I.F. transformer, P. IV, S. 10 Replace A. F. transformer, P. IV, S. 7

Replace R.F. and oscillator coil assembly, P. IV,

S. 2

Replace by-pass condensers, P. IV, S. 7

Check socket power unit by means of continuity

test,

and make any repairs

replacements

necessary, P. III, S. 6

Replace output transformer, P. IV, S. 14

Check cone coil and if open replace cone, P. IV,

S 1Z

Low Volume

Compensating condenser out of adjust -

ment

Trimming condensers out of adjustment

I.F. transformers not correctly aligned

Defective power cable

Defective R.F. transformer

Defective I.F. transformer Defective A.F. transformer

Dirty prongs of Radiotrons Defective by-pass condensers

Defective main tuning condenser Low voltages from socket power unit

Defective socket power unit

Adjust compensating condenser correctly, P.

II,

S. 14

Adjust trimming condensers, P. II, S. 17

Align I.F. transformers correctly, P. II,

S. 16

Repair or replace cable, P. IV, S. 9

Replace R.F. and oscillator coil assembly, P. IV,

S. 2

Replace I.F. transformer, P. IV, S. 10 Replace A.F. transformer, P. IV, S. 7

Clean prongs with fine sandpaper, P. II, S. 3

Replace defective by-pass condensers, P. IV, S. 7

Replace defective tuning condensers, P. IV, S. 4

Check socket power unit voltages with high re-

sistance D.C. voltmeter and A.C. voltmeter, P.

III, S. 2

Check socket power unit by means of continuity

tests and make any repairs

or replacements

necessary, P. III, S. 6

Poor Quality

Noisy Reception

Defective A.F. transformer

Defective by-pass condenser

Dirty contact arm of volume control

Dirty prongs on Radiotrons

Volume control advanced too far

Replace A.F. transformer, P. IV, S. 7

Replace defective by-pass condenser, P. IV, S. 7

Clean contact arm on volume control, P. II, S. 4

Clean prongs with fine sandpaper, P. II, S. 3

Reduce setting of volume control, P. I,

S. 6

Howling

Compensating condenser out of adjust-

ment

I.F. Neutralizing condenser out of ad-

justment

Defect in audio system

Open grid circuit in any stage

Microphonic Radiotrons

Adjust compensating condenser correctly, P.

II,

S. 14

Align and adjust I.F. transformers correctly, P.

II, S. 16

Check and repair any defect, P. II, S. 11

Check circuit and repair defect, P. III, S. 5

Interchange Radiotrons

Excessive Hum

Defective center tapped resistance unit

Socket plug position

Line voltage low

Defective S.P.U.

Replace defective resistance unit, P. IV, S. 12

Reverse socket plug

Solder line tap for low line voltage, P. I, S. 7

Check S.P.U. by continuity tests, P. III, S. 6

Radiotrons Fail

to Light

Operating switch not "On"

Defective operating switch

Defective input A.C. cord

Defective power transformer

No. A.C. line voltage

Turn operating switch "On"

Replace operating switch

Repair or replace A.C. input cord Replace power transformer, P. IV, S. 16

Turn A.C. line voltage "On"

Page 40

No. 600 Receiver Replacement Parts

6019

8479

6021

No.

Description

*Price

RECEIVER ASSEMBLIES

2010 Condenser-Fixed

condenser

160 mmfd.-

across secondary of

audio transformer

2015 Switch-Antenna switch

(not illustrated)

2267 Socket-Single Radiotron

socket with bake-

lite protective shield for UX-245

2269 Condenser-Fixed

condenser-Oscillator se-

ries,

oscillator

grid

condenser -740

mmfd.

2270 Resistor -40,000 ohms-Used as

oscillator

grid leak, and across primary of audio

transformer

2332 Knob-Station selector

or volume

control

knob (not illustrated)

2526 Spring-Spiral tension spring

for condenser

drive cord-Package of 5 (not illustrated)

2527 Scale-Tuning condenser

perforated

metal

scale-Package of 5

2531 Socket-Pilot

lamp

socket-Less

flexible

leads-Package of 5

2549 Resistor -1/2 megohm-Carbon type

filter re-

sistor-Package of 5

2560 Screen - Amber

colored

station

selector

screen-Package of 5.

2561 Drive Cord-Condenser drive

cord-Package

of 5

$.50

1.15

.50

.75

1.00

1.65

3.00 .60

1.20

No.

Description

*Price

2562 Pulley-Idler pulley for condenser drive cord

-Package of 5

2563 Resistor-Bleeder resistor 6000 ohms-Pack-

age of

2564 Resistor -1460 ohms-Bias resistor for UX-

245-Package of 5

2595 Spacer-Metal spacer for knobs-Package of

10 (not illustrated)

5806 Condenser-Fixed by-pass audio condenser,

.0024 mfd.-3 condensers in one unit

5809 Resistor-Oscillator resistor, and used across

primary

of 3d

I. F. transformer -3000

ohms

6021 Capacitor Pack in metal container-Compris-

ing five 1/2 mfd., two .05 mfd. condensers,

and 1 audio transformer

6022 Adjustable Condenser-R. F. Compensating

condenser or series trimming condenser

for oscillator

6024 Adjustable

Condenser-Parallel trimming

condenser for oscillator

6025 Resistor-Mid-tapped 60 -ohm filament resis-

tor-Package of 5

6026 Resistor-R.

bias resistor -465 ohms

tapped at 90 ohms

6027 Volume Control -550 ohms-Porcelain base

with 1/2 inch shaft, 2 inches long-Package

of 5

$1.60

3.00

3.30

.50

1.55

.75

18.75

1.00

.90

3.00

1.10

7.20

*Prices subject to change at our option

Page 41

No. 600 Receiver Replacement Parts

1111

7it

No.

Description

*Price

RECEIVER ASSEMBLIES (Cont'd)

6028 Socket -6 -gang,

UY-227

Radiotron

socket

with seven -gang protective shield

6029 Terminal

Strip-With

mounting

brackets,

link, 3 terminals and terminal screws

6030 Cable-Cable from receiver to S.P.U.

No.

Description

*Price

8479 Condensers-Tuning

condenser

assembly-

Comprising 3 condensers, drive, drive cord

$2.00

and spring-screws, washers, and nuts for

mounting dial

scale -2 screws and lock

.75

washers

for mounting screen

support -

2.40

Less scale and screen support

$15.00

8480

6028

2269

6026

2563

5809

8481

8482

5806

6029

6025

/2564

2267

6027

2549

2010

6030

2270

*Prices subject to change at our option

Page 42

No. 600 Receiver Replacement Parts

No.

Description

*Price

No.

Description

8483 Power Transformer -105-125 Volts -60 -cycle

transformer in metal container

*Price

$12.90

RECEIVER ASSEMBLIES (Cont'd)

8480 Coil Assembly-R. F. coil, detector coil, os-

cillator coil assembly, mounted on metal

8484 Power Transformer -105-125 Volts -25 -cycle

transformer in metal container (not illus-

strip

with 2

adjustable trimming

con-

densers and 1

R. F. compensating con-

denser, 1 oscillator series condenser, and 1

oscillator grid condenser

8481 Transformer -1st or 2d

I. F.

transformer

with adjustable condensers in metal con-

$6.60

trated)

8486 Reactor-Filter reactor in metal container...

8487 Filter

Condenser-Comprising

filter

con-

denser, by-pass condenser, output coupling

condenser and choke in metal container

24.90

10.05

14.25

tainer

3.90

8488 Terminal strip with 9 terminals and 7 ter-

8482 Transformer -3rd I. F. transformer with ad-

minal screws

1.30

justable condenser in metal container

4.20

REPRODUCER ASSEMBLIES

S.P.U. ASSEMBLIES

6018 Field Coil -330 -volt

(not illustrated)

6.60

2039 Switch-Power line

operating switch with

6019 Transformer-Output transformer

metal

leads

1.15

container

5.85

2267 Socket-Single Radiotron socket with bake-

8375 Cone -8" Corrugated paper cone with voice

lite protective shield for UX-280

.50

coil

for dynamic speaker

4.50

6031 Resistor -4800 ohms-Glazed porcelain

se-

8376 Ring-Metal

clamping

ring for

holding

ries resistor for plate supply (not illus-

cone (not illustrated)

.90

trated)

6032 Cable-Laced cable for wiring S.P.U.

(not

2.95

8390 Ring-Cardboard

seal

ring-Used between

baffle

board and cone support-Package

illustrated)

2.00

of 10 (not illustrated)

1.60

*Prices subject to change at our option

Page 43

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Page 44

1-H-29-5

GraybaR

QUALITY

Printed in U. S. A.

G. B. B. 67

Page 45

Grayb aR

550 Radio

"AC" Lighting Circuit Operated

GraybaR

QUALITY

INSTRUCTIONS

Grayb aR

ELECTRIC COMPANY

SUCCESSOR TO

Westera Electric

SUPPLY DEPARTMENT

Page 46

10.

0114

-,JSi4=4 c4,7=4

=v.=

-'40.N_MAr

..t;e2-

Page 47

Grayb aR

550 Radio Receiving Set

"AC" Lighting Circuit Operated

INTRODUCTION

The Graybar 550 Radio Receiving Set is a lighting circuit operated, antenna

type, shielded radio receiver, utilizing the new "AC" screen grid Radiotrons and a

new power -amplifier Radiotron introduced by the Radio Corporation of America.

The receiver, power unit, and electro-dynamic loudspeaker are enclosed in a walnut

finished cabinet, the front opening of which is covered with embroidered tapestry.

The circuit used in this

receiver includes two stages of tuned radio -frequency

amplification, a detector, and one stage of audio -frequency amplification.

The two stages of radio -frequency amplification employing "AC" screen grid

Radiotrons, UY-224, give performance equal to that of four tubes used in ordinary

tuned radio -frequency receivers. "AC" Radiotron UY-224 functions as the detector

with a consequent increase in the efficiency of the circuit. Fine quality of repro-

duction and ample volume are insured by the use of the power -amplifier Radiotron,

UX-245, in the single audio -frequency stage.

Radiotron UX-28o is used in the power unit to rectify the "AC" input for the

plate and grid supply for all Radiotrons, also for the loudspeaker field supply.

This receiver has a concentric tuning and volume control thereby insuring ease

of operation. A Lccal-Distant Switch is provided to retain the maximum high quality

operating characteristics of the receiving set for both strong local stations and weak distant stations.

A pilot lamp illuminates the selector dial when the power is on. As the Selector

is rotated, magnified images of the scale markings together with approximate kilo-

cycle (frequency) readings on the selector dial are projected upon a fixed translucent

dial screen. Images of the scale markings pass by a fixed index pointer on the screen.

Excellent sensitivity and selectivity are provided over the broadcast range from

550 to 1500 kilocycles (545 to 200 meters). The powerful built-in electro-dynamic

loudspeaker furnishes excellent reproduction, the quality of which is equally good at

reduced or full volume.

Part I

Installation and Operation

EQUIPMENT

One complete set of Radiotrons, as follows:

Three RCA Radiotrons UY-224. One RCA Radiotron UX-245.

One RCA Radiotron UX-280.

2. Two MAZDA No. 41 pilot lamps (one spare); T-3 bulb, miniature base, concen-

trated filament, 2.5 volts, 0.45 ampere (packed in instruction book envelope).

Antenna and ground equipment (see Part II).

Page 48

INSTALLATION

Preliminary

After unpacking the set remove the rear cover. Unwrap the power

cord and the antenna and ground leads and bring them out through the holes provided

in the bottom of the cabinet, as shown in Fig. 1.

Locate the receiver near an electrical outlet, where the antenna lead-in and ground

connections will be as short as practicable.

Antenna and Ground

Satisfactory operation

is dependent upon proper

installation of the antenna and ground (see Part II).

Connect the antenna lead (blue) of the receiver to the lead-in wire, and the

ground lead (black with blue tracer) to the ground wire (see Figs.

i and 5). Both

connections should be soldered and insulated.

Loudspeaker Make certain that all connections are secure at the loudspeaker

terminals (see Figs. 3 and 5).

Power Supply

Graybar 55o Radio Receiving Set should never be connected

to any circuit supplying other than alternating current, within the rated limits of

voltage and frequency (cycles) specified on the rating plate of the power unit (see

Fig. 3). Failure to observe this may result in damage to the receiver. If there is any

doubt about the rating of the house lighting circuit, consult the Electric

Light

and

Power Company before connecting the receiver.

(See also "'AC' Line Voltage",

Part II.)

No tube protector or line voltage reducer should be used with this receiver.

(See "Tube Protectors", Part II.)

Insert the attachment plug of the power cord in an electrical outlet.

Important-Never apply power to Graybar 550 Radio Receiving Set unless all

the Radiotrons are in the sockets.

Radiotron

Ux-245

Radiotron

UX-280

Fig.

1-Rear View

Spare Pilot

Lamp Socket

-gagazois.

Grid Lead

Caps

Three

Radiotrons

UY-224

_Small Metal

Shields

Antenna

Lead (Blue)

Ground Lead

(Black with

Blue Tracer)

with Cover Removed and Large Metal Shields Removed

Page 49

Metal Shields and Radiotrons-Unscrew the knurled nuts holding the

shield clamp (Fig. 3) in place. Remove the shield clamp and lift out the large metal

shields. Handle these shields carefully.

Insert the five Radiotrons, which

should always be handled carefully, in

the proper sockets as shown in Fig.

I. Fixed

Be sure that the " UX " Radiotrons are

Bracket'

so faced that the two large pins enter the

large holes, and that the base of each

Radiotron rests squarely against the

Pilot

socket. After the Radiotrons are inserted,

Lamp

press the grid lead caps (see Fig.

firmly down over the grid contacts of

the UY-224 Radiotrons.

Set the Power Switch (Fig. 4) to the

Socket

" ON " position, upward. Make sure that

Clamp

the five Radiotrons are lighted. Snap

the Power Switch "OFF", downward.

Push down on

the small metal

shields to make certain that they are

firmly in place. (See Fig. I.)

Replace each large metal shield carefully in its proper compartment. The shield

with one large and one small notch must be placed in the compartment to the left

(facing the rear of the cabinet) and with the large notch next to the selector dial.

After both shields are firmly in place, replace the shield clamp over the clamp bolts,

and replace the knurled nuts. These nuts should be tightened sufficiently to insure

holding the shields firmly in place; but excessive pressure, which may bend the shields,

is to be avoided.

Loudspeaker

Rating

Plate.

Fig. 2-Pilot Lamp Mounting

Showing Method of Installing Pilot Lamp-

Socket Clamp Slides Over Fixed

Bracket

Receiver

Shield

Clamp

Large Metal

Shields

Fig. 3-Rear View with Cover Removed-Large Metal Shields in Place

Page 50

Pilot Lamp-Turn the Selector (Fig. 4) counter -clockwise to the extreme position, so that the pilot lamp mounting will be accessible. Remove the socket clamp from the fixed bracket and screw one of the pilot lamps firmly into the socket (see

Fig. 2). Replace the socket clamp on its bracket. Insert the extra bulb into the spare pilot lamp socket, Fig. i.

Set the Power Switch to the "ON" position, upward. With the Selector in the

extreme counter -clockwise position, adjust the socket clamp on the fixed bracket until the zero mark of the scale, projected on the translucent dial screen (Fig. 4) is

approximately Y4 inch below the index pointer. Then switch off the power and

replace the rear cover.

OPERATION

To operate Graybar 55o Radio Receiving Set refer to Fig. 4 and proceed as follows:

Set the Power Switch to the "ox" position, upward. The pilot lamp should

light. An interval of approximately 3o seconds is required for Radiotrons

UY-224 to heat before satisfactory reception is possible.

Set the Local -Distant Switch to the " DISTANT" position.

Set the Volume Control in approximately the middle position. Then turn the Selector slowly in either direction. If no station is heard at any point,

advance the Volume Control in the clockwise direction slowly, while rotating

the Selector, until a station is heard.

Adjust the Selector for maximum signal strength.

Adjust to the desired volume by means of the Volume Control. Because of

the extreme sensitivity of the Graybar Receiving Set, a more satisfactory

adjustment is obtained, when receiving powerful nearby stations, by setting

the Local -Distant Switch in the "LocAL" position.

When through operating snap the Power Switch to the "OFF" position.

Power

Switch

-Dial Screen

Volume

III

Control

---Selector

Fig. 4-Panel and Controls

(Local -Distant Switch on Side Opposite Power Switch)

Note

If the Volume Control is too far advanced when receiving strong signals,

it may occur that the station can be tuned in over a broad continuous range on the

selector dial. In general, best reception of any station is obtained if the tuning is done

with the Volume Control set at the furthest counter -clockwise position at which the

station can be heard. After the correct setting of the Selector is obtained, the volume may be increased as desired with the Volume Control.

Page 51

Part II

General Information

The following suggestions are offered to assist the user in obtaining the best

performance from Graybar sso Radio Receiving Set.

"AC" Line Voltage-Both 105/125 volt models (5o/6o and 25 /40 cycles) of the

Graybar 55o Radio Receiving Set are originally connected for normal operation on

voltages above 115. The original connection should be left unchanged unless it is defi-

nitely determined, by consulting the Graybar Radio Dealer or the Electric Light and

Power Company, that the supply voltage is normally below this value. Provision is

made for adapting the receiver to voltages below 115 by a simple wiring change

within the receiver. When such a change is required, it should be performed by the

Graybar Radio Dealer.

Tube Protectors-The power transformer in this receiver is designed to supply

correct voltages to the Radiotrons, without the addition of a tube protector or line

voltage reducer. A tube protective device of any kind, used in series with the power

supply, will reduce the voltage supplied to the receiver so that the Radiotrons will

not receive their proper voltages and therefore will not operate at highest efficiency. For this reason it is recommended that no line voltage reducing device be used with

this receiving set.

Power Supply-Reception may possibly be improved by reversing the plug

(Fig. 5) at the electrical outlet.

Metal Shields-Be sure that the metal shields are always firmly in place. Radiotrons-Improved results may sometimes be obtained by rearranging the

UY-224 Radiotrons, all other Radiotrons remaining in their respective sockets.

Before interchanging these Radiotrons, switch off the power. (See "Important ",

Part I.)

Volume-Adequate control of volume can be obtained with the Volume Control

and the Local -Distant Switch. Reduction of volume should never be accomplished

by adjustment of the Selector. The Local -Distant Switch should be set

in the

" LOCAL" position and the Volume Control advanced whenever by so doing the desired

volume can be obtained.

Selector Dial

The Selector scale is arbitrarily graduated from "o" to " ioo".

Approximate kilocycle (frequency) values are indicated on the left side of the scale. The dial settings may be recorded on the Station Log, at the end of this book.

Antenna

(a)

Outdoor Type-A single -wire (No. 14 bare copper is recommended) out-

door antenna 3o to 5o feet long will usually provide good reception. The shorter

antenna is preferable in a locality near high -power broadcast stations. A longer

antenna may give improved results in a locality distant from broadcast stations.

The antenna should be isolated from other objects. It should be erected as high

as possible and at right angles to all electric light and power lines and must not cross

either above or below such lines. The antenna and lead-in should be supported by high-

grade glass or glazed porcelain insulators, and the lead-in should be spaced a foot or

more from the building. All splices should be soldered.

The lead-in and ground connections should be separated from one another and

be as short and direct as practicable. It is preferable that the lead-in wire be a con-

tinuation of the antenna itself, and where brought through the wall or window frame

it should be insulated therefrom by some means, such as a porcelain tube.

An outdoor antenna should be protected by an approved lightning arrester, in

accordance with the requirements of the National Board of Fire Underwriters.

Page 52

Power

Switch

..,--Interchangeable

Black and Red

(110-V. Tap)

Black with Red

Tracer(12 0-V. Lead)

Black

.%Ns

POWER UNIT

LOUDSPEAKER

Black

-Red

Black with

--Green

Yellow Tracer

Attachment

Power Cord

Plug

Local -

Distant

Switch

Yellow

III

ommimme

wfft==

MIN

III

mmmmc

MIM

1111

M111111

lack

000.

Green

UY-224

UY-224 BUY -224

RECEIVER UNIT

Black

Blue Tracer

Fig. 5-Cabinet Wiring of Graybar 550 Radio Receiving Set

I I

ICI

I I

1!I

Ground-.-

Blue

Page 53

(b)

Indoor Type-An indoor antenna is not as effective for distant reception

as a properly installed outdoor antenna. Where installation of an outdoor antenna

not practicable, satisfactory results may be obtained by using 3o to so feet of insulated

wire inside the building. The size of the wire is not particularly important, though

No. i8 bell wire is suggested. In buildings with metal lath, satisfactory results are

not always possible with this type of antenna. Under such conditions, various arrange-

ments of the indoor antenna may be tried.

Ground-A good connection to ground is as important as a well constructed

antenna. Definite instructions cannot be given, as conditions vary in different loca-

tions. Water pipes or steam pipes generally make good grounds. The use of gas pipes

should be avoided. The ground lead should be connected by means of an approved

ground clamp to a section of the pipe that has been scraped thoroughly clean. If

water or steam pipes are not available, a pipe or metal rod may be driven into the

ground to a depth of several feet. The success of this type of ground depends upon

the presence of moisture in the soil.

Part III

Maintenance

Radiotrons-Before inserting or removing Radiotrons always be sure that the

current is switched off. (See "Important", Part I.)

The contact pins of all Radiotrons, also the grid contacts at the top of the UY-221.

Radiotrons, should be inspected periodically and kept clean.

It is a good plan to have available at least one new RCA Radiotron of each type.

Occasionally, the condition of each Radiotron in use should be checked by substituting

a new one and comparing results in reception, both local and distant.

Power Supply-Should the pilot lamp and Radiotrons fail to light with the

Power Switch in the "ON" position, it is probable that the receiver is not properly

connected to the power supply. Make sure that the attachment plug is properly

inserted in the electrical outlet and that the current is not switched off at any point.

Volume Control-If the operation of the Volume Control should at times

produce a grating sound in the loudspeaker, this may be remedied by turning the

control back and forth between the extreme positions a few times in order to remove any foreign material which may have collected on the control resistance.

Antenna and Ground-A decrease in receiving range and volume may be

caused by loose or corroded connections in the antenna and ground circuit, or by

an accumulation of dirt or soot on the antenna insulators.

Pilot Lamp-Renewal bulbs (see "Equipment", Part I) may be purchased

from any Graybar Radio Dealer. Before removing the pilot lamp from its bracket (see "Pilot Lamp", Part I) always switch off the power.

In order that station settings will not be changed when a new bulb is inserted,

the socket clamp should be adjusted so that any one station (the previous setting

for which is accurarely known) is received at the same scale reading as before.

Page 54

Graybar Radio Dealer-The Graybar Radio Dealer is required

to test this

receiver and assure himself that it is in satisfactory operating condition when installed.

This receiver is guaranteed to be free from defects

as outlined on the guarantee

tag accompanying the instrument. Should any part become defective within the

guarantee period, the Dealer will furnish a new part to replace the defective one.

A reasonable charge may be made for installing such parts.

If any service on this receiver is needed, either before or after expiration of the

9o -day guarantee, the Graybar Radio Dealer from whom it was purchased should

be consulted. If this Dealer cannot be reached because of change in location,

or other

reasons, the nearest Graybar Radio Dealer should be consulted. Graybar Radio

Dealers are organized to handle customers' service needs either by their

own service

department or by arrangement with the Graybar distributing house.

IMPORTANT

The Graybar 90 -day guarantee on this Receiver is not effective unless

the Graybar Guarantee Tag is countersigned and dated at time of sale by

the Graybar Radio Dealer from whom it was purchased. If

you have not

received the signed Guarantee Tag, be sure to have the Graybar Radio

Dealer give it to you immediately.

NOTICE

This device is licensed by the Radio Corporation of America only for certain

restricted uses set forth in a notice permanently attached to it.

Page 55

STATION LOG

Date

Call

Letters

Location

Frequency

Kilocycles

Wave_

length

Selector

Dial

Setting

Page 56

Grayb aR

E LE CTRI C COMPANY

SUCCESSOR TO Western Electric SUPPLY DEPARTMENT

Offices in 72 Principal Cities

Akron Denver

Albany Detroit

Asheville Duluth

Atlanta Flint

Baltimore Fort Wayne

Beaumont Fort Worth

Birmingham

Grand Rapids

Boston Hammond

Brooklyn Harrisburg

Buffalo Hartford

Charlotte Houston

Chicago Indianapolis

Cincinnati Jacksonville

Cleveland

Kansas City

Columbus

Knoxville

Dallas

Los Angeles

Davenport

Memphis

Dayton Miami

Milwaukee Minneapolis

Mt. Vernon (N.Y.)

Nashville

Newark

New Haven

New Orleans

New York

Norfolk

Oakland

Oklahoma City

Omaha

Philadelphia

Pittsburgh

Portland

Providence Reading Richmond

Roanoke Rochester

St. Louis

St. Paul

Salt Lake City

San Antonio

San Francisco Savannah Seattle

Spokane Syracuse

Tacoma

Tampa Trenton

Toledo

Wichita

Worcester

Youngstown

GB -R-38

Printed in U.S.A.

Page 57

Grayb aR

Electro-Dynamic Loud Speaker Table

No. 33

INSTRUCTIONS

Grayb aR

ELECTRIC COMPANY

SUCCESSOR. TO

Weston., Electric SUPPLY DEPAATS.NT

Page 58

Grayb aR

Electro-Dynamic Loud Speaker Table

No. 33

Introduction

Graybar Electro-Dynamic Loud Speaker Table No. 33 is designed for use with

any broadcast receiver having a power output stage or a separate power amplifier unit.

Its powerful electro-magnetic field, and its correspondingly large baffle area, provide

unusual sensitivity and permit extraordinary volume without distortion or overloading.

The table itself is so designed that it will accommodate practically any type of

table model cabinet.

The electro-dynamic speaker mechanism complete with step down output trans-

former and junction rectifier field supply unit, is solidly mounted to prevent vibration.

Flexible cords are provided for connecting to the electrical outlet, and to the output of

the radio receiver. A receptacle is provided on the bottom of the table for plugging in

an "AC" operated receiver or power amplifier, or an "AC" operated accessory to a

battery type receiver.

Installation

Unpacking and Assembling:

After removing the cabinet and the unmounted loudspeaker mechanism from the

shipping container, place the table front downward on a rug and remove the back

cover, which is fastened by screws at its sides. Place the mechanism in position on the

front baffle as shown in Figure 3, and fasten by the four supporting Wing -Nut bolts.-

Be sure to tighten these four Wing -Nuts with a wrench or pliers, to make se-

cure and to prevent vibration.

Connect the leads of the cable at the top of the cabinet, either way, to the middle

terminals of the rectifier stacks, as shown in Figure 3 (see that the lead clamped to the

underside at each terminal remains connected). Make sure that the two leads of the

input cord A (Figure 3) are securely connected to the terminals at the lower left portion

of the loudspeaker frame. Unwrap the input and power cord, placing them through

their proper bushings in the bottom of the cabinet.

Replace the back cover of the

cabinet and fasten with the screws.

Connections to Receiver:

After having placed the receiving set on top of the table, connect the two pin

terminals of the Input Cord A (Figure 3) either way to the output pin jacks or binding

posts of the receiver (or separate power amplifier if used).

Page 59

INSTALLATION Continued

No external output transformer is necessary. The step down output transformer

(Figure 3) serves to match the output of the power stage to the low impedance coil

of the loud speaker.

If the receiver is "AC" lighting socket operated, insert the attachment plug of its

power cord in the receptacle "C" (Figure 3) on the

bottom of the baffle board.

If a battery type receiver with a "B" battery eliminator is used, the power cord

of the eliminator should be plugged into receptacle "C" (Figure 3). Trickle chargers

when used with storage batteries should not be connected to this receptacle.

If the loudspeaker No. 33 is operated from an "AC" power amplifier unit, the power

cord of the amplifier should be plugged into the receptacle "C". If the receiver is

entirely battery operated, the receptacle "C" (Figure 3) will not be used.

Connection to Power Supply:

Graybar Electro-Dynamic Loud Speaker Table No. 33 is to be connected to

25 to 60 cycle, 110-125 volt alternating current only-not direct current. Failure to com-

ply with this requirement may result in damage to the unit. If there is any doubt about

the rating of the house lighting current consult the Electric Light and Power Company before connecting Loud Speaker Table. The voltage and frequency rating of the "AC" receiver, power amplifier, or "B" eliminator should conform to the rating of the house

lighting circuit.

Set the switch "B" (Figure 3) to the "off" position.

Insert the attachment plug

of the cord "D" (Figure 3)

in an electrical outlet.

Important - The back

cover should never be re -

Rectifier

moved without first discon-

Stacks

fleeting the power cord from

the electrical outlet.

Step -Down

Output

Transformer

FIGURE 3

Rear view of Graybar Loud Speaker Table No. 33

with back cover removed showing manner of wiring.

Page 60

INSTALLATION Continued

Operation:

Graybar Loud Speaker Table No. 33 is placed in operating condition (field

excited) b> setting the switch "B" to the "on- position.

The switch on the radio

set, if either "AC" or battery type, must also be turned on to obtain reception.

If a

power amplifier or "B" battery eliminator is used, the switch on the receiving set may also control the current to either. This feature varies with the type of equipment used.

Caution- The switch on the loudspeaker table and the switch on the receiving set

operate separately, so that, it is always necessary to place both switches in an "off"

position \ he n no reception is desired. Switch "B" (Figure 3) as connected cannot be

used to control the receiving set or any accessories connected to receptacle "C".

Maintenance

Graybar Loud Speaker Table No. 33 should require no attention.

If it fails to

operate at any time check the following:

I. Be sure the attachment plug is securely plugged into the

electrical outlet,.

2. Be sure the radio set is properly inserted into the receptacle

"C" (Figure 3).

3. Check all connections on Input Cord "A" (Figure 3). I. Be sure all switches are turned "on".

If faulty reproduction should develop, look first for difficulties in the radio receiver

(and power amplifier unit if used). The receiving equipment

may he tested by substi-

tuting another loudspeaker.

If any difficulty arises which is not readily traceable to the power supply

or receiv-

ing, apparatus, the Graybar Radio dealer, from whom you purchased the Loud Speaker Table should be consulted.

License Notice.

This device is licensed by the Radio (:orporation

merica only for certain restricted uses set

forth in a notice permanently attached to it.

Graybar Loud Speaker

Table :Vo. 33 makes a

splendid

combination

with any radio receiv-

ing set of suitable size

to fit on lop.

11 is espe-

cially designed to ac-

commodate the Graybar

330 and Graybar 310.

as pictured.

2 21.?

R t3

Page 61

GRAY

AR RADIO

311

SERVICE NOTES & REPLACEMENT PARTS

Grayb aR

ELECTRIC COMPANY

SUCCESSOR TO Western Electric SUPPLY DEPARTMENT

Page 62

CONTENTS

Page

Introduction

Service Data Chart

PART I -INSTALLATION

Page

Antenna (Outdoor Type) 4

Antenna (Indoor Type) 5

Ground

Radiotrons

Page

Adjustment for Low Line Voltages

Attaching Legs to Cabinet

Refinishing Marred Surfaces

Knobs

Wave Trap

PART II -SERVICE DATA

Antenna System Failures Radiotron Sockets Radiotron Prongs Loose Volume Control and Low Volume

Tuning Condensers Out of Alignment

Hum

Loudspeaker Polarity

Audio Howl

Uncontrolled Oscillation

Adjustment of R.F. Compensating Condenser

Distorted Reproduction

Pilot Lamp

Filter Condenser and Output Condenser and

Choke

PART III -ELECTRICAL TESTS

Voltage Readings

Continuity Tests

Voltage Supply System

PART IV -MAKING REPLACEMENTS

Replacing Volume Control Replacing Radio Frequency Coils

Replacing Radiotron Gang Sockets

Replacing Main Tuning Condensers and Drive

Replacing By -Pass Condenser

Replacing Audio Frequency Transformers

Replacing Condenser Drive Cable

Replacing Tuning Dial

Replacing Filter Condenser, Output Choke and

Condenser Assembly

Replacing Either Power Transformer or Filter

Reactor

PART V -NO. 311 RECEIVER REPLACEMENT PARTS

Receiver Assemblies

S.P.U. Assemblies

Receiver Assemblies Continued

ILLUSTRATIONS

Graybar 311 Set

Top View of Receiver and S.P.U. Chassis

Sub -Chassis View of Receiver and S.P.U.

Schematic Circuit Diagram of 311 Set

Radiotron Sequence

Spade Tool for Testing Alignment of Gang

Condensers

Internal Connections of Condensers

Radiotron Socket Contacts

Schematic Circuit of Voltage Supply System

Wiring Diagram of Receiver

Wiring Diagram of S.P.U.

Gang Tuning Condenser Drive Mechanism and

Cable

311 Receiver Replacement Part, Plate No. 5663

311 Receiver Replacement Part, Plate No. 2515

311 Receiver Replacement Part, Plate No. 2267

19 19

13 14 16

22 23

Page 63

OUTPUT CONDENSER

FILTER

POWER PILOT

TUNING

AND CHOKE AND

REACTORS

TRANSFORMER

LAMP CONDENSERS

FILTER CONDENSERS

R. F:

DETECTOR.

OUTPUT

UX-280

COMPENSATING TRIMMING

R.F. COIL

OPERATING SWITCH

PIN JACKS

SOCKET

CONDENSER

CONDENSER ASSEMBLY

Figures 2 and 3-Top view of receiver assembly and socket

power unit showing location of parts

Page 64

SERVICE NOTES FOR GRAYBAR No. 311

RECEIVER

(105-125 Volts, 50-60 Cycle A. C.)

INTRODUCTION

The Graybar No. 311 is a socket powered six-tube,

tuned radio frequency receiver utilizing

RCA Radiotrons UX-226, UY-227, UX-171A and the full

wave rectifier Radiotron UX-280 in

the Socket Power Unit (referred to in the text

as S.P.U.)

It operates on 105-125 volts, 50 to

60 cycle A.C. lines.

It is also supplied in models designed for 105-125 volts, 25-40 cycle A.C.

lines.

The difference between this model and the 50-60 cycle

is the power transformer. The

Service Notes apply to both models.

Figure 1 illustrates a front view of the cabinet and Fig-

ures 2, 3, 4 and 5 a top and bottom view of the various units in the Receiver Assembly

and

the Socket Power Unit.

The following principles are incorporated in the circuit design-See

Figure 6.

(a) A single control, three -gang condenser is employed

to tune two of the radio fre-

quency circuits and the detector circuit.

(b) An aperiodic antenna

or first R.F. circuit, eliminates the necessity for a separate

an-

tenna tuning control.

to the first R.F. amplifier stage.

This is the most practical method of volume control for

use with A.C. Radiotrons

and gives a smooth control of volume without distortion.

(d) Raw A.C. of the correct voltage is used for filament

heating of all Radiotrons.

(e) The three R.F. stages and the first audio stage receive

a plate voltage of 135 volts

in conjunction with a negative grid bias of 9 volts.

The detector receives 30 volts

plate supply.

The last audio stage receives a plate voltage sufficient to provide

ample

loudspeaker output. The plate and grid voltages

are supplied by means of a built-in

"B" and "C" power supply unit using Radiotron UX-280

as the rectifying device.

Figure 7 illustrates the sequence of the Radiotrons in the

receiver, omitting Radiotron

UX-280 in the socket power unit.

From right to left, when facing the front of the

receiver,

the Radiotron sequence is as follows:

Radiotron No. 1 is an untuned stage of radio frequency

amplification.

It is coupled di-

rectly to the antenna and ground.

Radiotron No. 2 is a stage of tuned radio frequency

amplification, and is tuned by the

first of the gang condensers.

Radiotron No. 3 is the second stage of tuned radio frequency

amplification.

It is tuned

by the second of the gang condensers.

Radiotron No. 4 is the detector and is tuned by the third

of the gang condensers.

Radiotrons Nos. 5 and 6 are respectively, the first and

second stages of audio frequency

amplification.

The last stage, Radiotron No. 6, employs

power amplifier Radiotron UX-171A.

An output filter protects the loudspeaker windings from

any D.C.

The following notes are published for the guidance of

those called upon to locate and

remedy any trouble that may occur.

The text is divided into four parts, Part I-Installa-

tion ;

Part II-Service Data; Part III-Electrical Tests, and Part

IV-Making Replace-

ments.

PART I-INSTALLATION

[1] ANTENNA ( Outdoor Type)

Due to the high sensitivity of the No. 311 receiver the

antenna length need only be

approximately 25 to 50 feet.

It should be erected as high as possible and be removed from all

obstructions.

The lead-in should be a continuation of the antenna itself, thus

avoiding all

Page 65

splices which might introduce additional resistance and in time corrode sufficiently to seri-

ously affect reception.

If it is absolutely necessary to splice the lead-in to the antenna, the

joint must be carefully soldered to insure a good electrical contact.

Clean off all excess flux

and tape the connection to protect it from the oxidation effects of the atmosphere.

High grade glass or porcelain insulator supports are required and at no point should the

antenna or lead-in wire come in contact with any part of the building.

Bring the lead-in

wire through a porcelain tube insulator to the inside of the house for connection to the re-

ceiver.

The antenna should not cross either over or under any electric light, traction or power line

and should be at right angles to these lines and other antennas.

An outdoor antenna should

be protected by means of an approved lightning arrester, in accordance with the requirements

of the National Fire Underwriters' Code.

[2] ANTENNA ( Indoor Type)

Where the installation of an outdoor antenna is not practical, satisfactory results may gen-

erally be obtained by using an indoor antenna of about 20 to 40 feet of insulated wire strung around the picture moulding or placed under a rug.

In buildings where metal lathing is em-

ployed, satisfactory results are not always possible with this type of antenna.

Under such

conditions various arrangements of the indoor antenna should be tried to secure satisfactory

results.

An indoor antenna is not as efficient as a properly installed outdoor antenna.

[3] GROUND

A good ground is quite as important as the antenna. No specific recommendations can be

given in this matter as conditions vary in different locations.

Water and steam pipes usually

make good grounds.

Gas pipes usually make poor grounds and, as a rule, are to be avoided.

If neither water nor steam pipes are available, a pipe or metal rod may be driven into the

ground to a depth of several feet.

The success of this type of ground depends upon the mois-

ture present in the soil.

The ground lead should be connected by means of an approved

ground clamp to a section of pipe that has been scraped and thoroughly cleaned.

The connection should be inspected from time to time to make certain that a clean and tight electrical contact exists between the clamp and pipe.

The service man should experiment with various

grounds, and employ the one giving the best results.

[4] RADIOTRONS

Four Radiotrons UX-226, one UY-227, one UX-171A and one UX-280 are used.

The lo-

cations of these Radiotrons are plainly designated on each socket.

Be careful not to insert a

Radiotron UX-226 in the UX-171A socket, as immediate filament burn -out will result when

the current is turned "ON."

Connect the loudspeaker to the output pin terminals and insert the A.C. input plug into a

socket outlet of correct voltage and frequency. Turn "ON" the operating switch. After about 30 seconds the Radiotron UY-227 will glow dimly, indicating that the receiver is in operat-

ing condition.

If no signals are heard when tuning to a station known to be broadcasting,

examine the Radiotrons.

Possibly one Radiotron has been damaged in transit.

Interchanging

with one or more known to be in operating condition will isolate the damaged one.

If there is an excessive hum present during operation :

(a)Reverse the A.C. input plug at the socket outlet.

(b) Interchange the Radiotrons UX-226 in the R.F. stages with the one in the first A.F.

stage, and use the combination that gives least hum. Then interchange the three in

the R.F. stages for the best results while tuned to a broadcast station.

[5] ADJUSTMENT FOR LOW LINE VOLTAGES

A lead is provided on the side of the S.P.U. for use when the No. 311 receiver is connected

to lines, the voltage of which never exceeds 115 volts. A good plan is to allow the lead to re-

main as connected in manufacture unless unsatisfactory operation is experienced.

Should

such adjustment be necessary, however, proceed as follows:

(a) Remove top from metal cabinet.

Page 66

(b) Connected to the operating switch will be found two taped connections, one of

which has a transformer lead (black with red tracer) connected to a black switch

lead. Untape and unsolder this connection and then tape up the black with red

tracer lead so that it will not ground or short to other parts.

Untape this lead and

clean the end for splicing.

(d) Splice this lead just untaped to the black lead from the switch that has been re-

leased. Solder and tape securely.

The 110 -volt tap of the transformer is now properly connected and the receiver may be

used on 105-115 volt lines with maximum efficiency.

Figure 15 illustrates these changes to

be made.

GRID AND PLATE

SUPPLY RESISTOR

CLAMP FOR HOLDING

A. F. BY-PASS

INPUT LEAD

CONDENSER

A. F.

TRANSFORMERS

CENTER TAPPED

BY-PASS

DETECTOR

VOLUME

RESISTORS

CONDENSERS

SERIES RESISTOR PLATE RESISTOR CONTROL

Figures 4 and 5-Sub-chassis view of receiver and socket power unit showing location of

parts

[6] ATTACHING LEGS TO CABINET

Four legs are provided with the No. 311 receiver that must be attached by the dealer

the purchaser.

The following step-by-step procedure may be used:

(a) Remove the cover and place the cabinet upside down

on a soft blanket or rug in a

place convenient for work.

(b) Place the hollow leg section over the foot

on the cabinet so seam is toward back.

so one side with design faces

toward the front.

(d) Thread long bolt through center of casting and leg and

screw tightly into threaded

section provided in cabinet foot.

(e) Insert metal plug, flanged side inward, into hole

over bolt head and tap lightly to

secure it.

(f)

Repeat the procedure on each leg.

[7] REFINISHING MARRED SURFACES

Should the surface of the No. 311 cabinet become scratched

or marred either when in-

stalling or after use, it may be easily refinished in the

same manner that wood is refinished.

In other words, it may be stained, lacquered, varnished and polished.

Page 67

[8] KNOBS

The No. 311 set uses an improved type of push knob on the

station selector similar to that

used on the Graybar No. 330 and two pendant type push knobs on

the operating switch and

volume control.

These knobs may be removed by simply pulling them from

their shafts and

replaced by pushing them on.

Care should be taken when replacing the knobs to make sure

the small dielecto spacing washers are placed over the

shaft before the knob is put on so

the knob will not bind against the cabinet.

[9] WAVE TRAP

Due to wide variations in broadcast receiving

conditions in different sections of the

country, the performance of any radio receiver in any

given location depends upon the local

receiving conditions existing at that point.

,VOLUME CONTROL

THREE -GANG TUNING CONDENSER -A

COUPLING

UX-226

Ie TUNED R.F.

II VIP TUNED R.F

UX-226

=. f=a

L.7.-

DETECTOR

RIMMING

CONDENSER

DETECTOR

.0012 MPS.

UV -227

30,000.n.

0 0

IS! A.F.

PWR.

'FILTER REACTOR

U X-226

5111111111111

OUTtUT

1.00016

MFD.

.5 MFD.

R.F.

COMPENSATING

CONDENSER.

PILOT

LAMP

IOUTPUT 0

5 MED.

CHOKE

&WAWA.

1600.n.

1 MED

MED.

1900 XL

POWER

TRANSFORMER

MED.

440IL

110 VOLT

LEAD

OPERSTING

SWITCH

S.C. INPUT

PLUG

Figure 6-Schematic circuit diagram of receiver and socket power

unit-all grounds are

connected to frame and metal cabinet

Receivers located in the vicinity of powerful broadcasting stations

receive the signal

from such stations with great intensity over a large number of scale

divisions of the receiver.

If it is desired to receive a relatively distant station whose frequency

assignment is compara-

tively close to that of the local station, it is impossible to do so without

interference.

To satisfy the No. 311 set user located in districts where bad

receiving conditions exist, a

Wave Trap has been designed and will be carried by Graybar

Distributing Houses as an

accessory.

The function of the wave trap is to absorb a large portion of the energy

of the powerful

local signal picked up by the antenna, thereby reducing the effect of the

powerful local signal

to a value comparable with that of more distant stations.

This wave trap is very efficient in design, is neat in appearance,

and is simple to install

and adjust.

It may be adjusted to absorb a strong signal at any point on the

No. 311 dial

scale.

After it has once been adjusted to absorb the strong local signal

causing interference

at a particular location, it needs no further adjustment or

attention.

It is intended that this Wave Trap shall be located on the top of the

chassis frame at

the extreme left end viewing the set from the front.

Installation can be made in five or ten

minutes without removing the chassis from the cabinet.

Complete installation and adjust-

ment instructions accompany each unit.

Page 68

PART II -SERVICE DATA

[1] ANTENNA SYSTEM FAILURES

A grating noise may be caused by a poor lead-in connection to the

antenna or the antenna

touching some metallic surface, such as the edge of

a tin roof, drain pipe, etc.

By disconnect-

ing the antenna and ground leads the service

man can soon determine whether the cause of

complaint is within or external to the receiver and plan his service

work accordingly.

[2] RADIOTRON SOCKETS

The sockets in No. 311 receiver are the standard gang UT. and UY type. Care

must be exer-

cised when inserting Radiotrons in their sockets.

A socket contact may not be in its cor-

rect position and forced insertion of a tube will bend

or break it.

If care is exercised and

the Radiotron inserted gently, little trouble will be experienced with socket

contacts. A bent

one will be noticeable on inspection and may be corrected by inserting a narrow instrument

in the socket hole and pushing the contact into its correct position. A badly

bent or broken

socket contact should be replaced.

A.F.

TO LOUDSPEAKER

DETECTOR

TO ANTENNA

3RD

2No

SST

R.F.

RADIO FREQUENCY

AUDIO FREQUENCY

Figure 7-Radiotron

sequence in No. 311 Receiver

The bakelite Radiotron guide shields

used in No. 311 set will prevent

any possible shock

from contact with high voltages in

the socket when inserting the Radiotrons.

The prongs of the tubes fit into this

shield opening very snugly and require only

a twist

until the prongs find the correct holes

into which they fit.

[3] RADIOTRON PRONGS

Dirty Radiotron prongs

may cause noisy operation or change the resistance of the fila-

ment circuit sufficiently to

cause a hum in the loudspeaker. They should therefore be cleaned

with fine sandpaper periodically to insure

good contact.

The use of emery cloth

or steel wool is not recommended.

Before reinserting Radio-

trons in their sockets wipe the

prongs and base carefully to make certain that all particles

of sand are removed.

Care should be exercised to

see that the two large pins and two small pins of the Radio-

trons match the socket holes.

The UY-227 Radiotron has five

prongs, all of the same size,

and will fit in the socket only

one way.

If a Radiotron will not fit into

a socket without con-

siderable pressure, look for excessive solder

on one or more of the prongs. Excessive solder on

the prongs may be removed with

a file or knife.

[4] LOOSE VOLUME CONTROL

AND LOW VOLUME

A loose volume control contact

arm may cause noisy or intermittent operation.

It should

be bent slightly so that it makes firm contact

against the resistance strip.

To do this it is

necessary to remove the receiver assembly and S.P.U. from the

cabinet as described in Part

IV, Section 1.

The volume control is then accessible.

It can be released by removing the

two screws that hold it to the metal frame.

Page 69

[5]

Low volume even on local stations may b e due to one of the following causes:

(a) Defective antenna and ground system. A poor antenna and ground system or one in

a shielded locality may cause weak signals.

The suggestions given in Part I, Sec-

tions 1, 2 and 3 should be followed if trouble of this kind is experienced.

(b) R.F. compensating condenser out of adjustment.

If this condenser is badly out of

adjustment it will have the effect of making the receiver very insensitive. To adjust

correctly refer to Part II, Section 10.

Should the R.F. transformers become damaged so that

they do not properly match, weak signals may be the result.

(d) Defective A.F. transformer.

An open or short in the A.F. transformers may cause

weak signals and distorted reproduction.

TUNING CONDENSERS OUT OF ALIGNMENT

If the tuning condensers are out of alignment, line up as follows :

(a) Procure or construct a tool as illustrated in Figure 8.

(b) Remove the receiver assembly and S.P.U. from the cabinet as described in Part IV,

Section 1, and place in operating condition.

Tune in a signal, either broadcast or a

modulated oscillator of about 1400 K.C. and adjust the volume control so that the

signal is very weak.

condensers and note if an increase of signal is experienced.

If the condensers are

in alignment the signal should decrease.

If the signal increases, that particular

condenser is slightly low in capacity, which can be corrected by bending the two end

rotor plates toward their adjacent plates slightly until the test with the "paddle"

gives a decrease rather than an increase in signal.

(d) After checking the condenser for low capacity they may be checked for high capacity

by taking the ring of the tool and inserting it successively in the center of the three

R.F. coils.

This should give a decrease of signal.

If it increases then the end rotor

plate of the condenser that tunes the coil should be bent away from its adjacent

rotor plate.

This should be bent until inserting the ring 'in the coil will give a

decrease of signal rather than an increase.

The detector tuning condenser is pro-

vided with a small trimming condenser for aligning this circuit.

Instead of bend-

ing the plate of the condenser adjustment should be first attempted at the trimming

condenser.

In most cases this will cover all aligning adjustments required in the

detector stage.

(e) After checking at 1400 K.C. a station or oscillator signal about 600 B.C. should

be tuned in and the condensers completely checked at this frequency.

Any addi-

tional necessary adjustments should be made.

(f) After completion of all tests, return the receiver to its cabinet in the reverse manner

of that used to remove it.

[6] HUM

Part I, Section 4, describes the method to eliminate ordinary hum in a No. 311 receiver

when making an installation.

If a pronounced hum develops during operation check the

following :

(a) Low emission Radiotron UX-280. A low emission rectifying tube will cause exces-

sive hum and unsatisfactory operation.

(b) Shorted filament condenser.

There are two .1 mfd. condensers hooked in series

across the UX-226 filaments with the center tap grounded.

A short of either of

these condensers will cause loud hum and imperfect operation of the receiver.

A short or open in any of the center tapped

resistances connected across the various filament supplies will cause a loud hum.

(d) Any open of the several grounding connections in the receiver or defective voltage

supply resistances may cause a certain amount of hum.

These defects will have a

pronounced effect on the general operation of the receiver which will be more notice-

able than the additional hum.

Check by means of the continuity test given in Part

III, Section 3.

Page 70

A mechanical hum caused by vibration of loose laminations in the power transformer

may be corrected by removing the power transformer from the S.P.U. as described in Part IV, Section 10, and heating it in a slow oven.

The open end should be kept up and the com-

pound heated sufficiently to allow it to adhere to the laminations of the transformer.

After

heating, the transformer should be allowed to cool for at least 24 hours and then returned

to the S.P.U.

[7] LOUDSPEAKER POLARITY

The use of an output filter in the No. 311 receiver makes unnecessary any adjustment for

polarity of the output current. Any type of loudspeaker (either horn, magnetic type cone or

dynamic type cone) can be connected in the manner that gives the most pleasing reproduction.

5' APPROX.

BAKELITE"

HEAVY WIRE RING)

----OLD CONDENSER PLATE

Figure 8-Tool for testing electrical

alignment of gang tuning condensers

[8] AUDIO HOWL

Audio howl may be caused by :

(a) Open A.F. condenser connections. An open connection to either

of the A.F. con-

densers, one connected from plate to cathode of the detector

and the other from

grid to filament of the first A.F. tube, may cause a howl.

(b) Open by-pass condensers. An open .5 mfd. by-pass condenser

connected across the

detector plate resistor connection may cause a howl.

A gradually developed howl is prob-

ably due to the loudspeaker causing the receiver Radiotron elements

to vibrate.

overcome this condition, interchange the

Radiotrons in the receiver or change the

relative angle between the loudspeaker and the receiver.

In extreme cases it will

be necessary to increase the distance between the receiver and the

loudspeaker.

[9] UNCONTROLLED OSCILLATION

Uncontrolled oscillations in any part of the tuning range may be

caused by :

(a) Poor ground.

Install ground system as indicated in Part I, Section 3.

(b) An open connection in any of the several ground leads in

the receiver.

Any high resistance joint throughout the re-

ceiver may cause oscillation.

(d) A defect in the R.F. coil system. A short in any of

the concentrated primary coils

or the condenser shunted around them may cause

the receiver to oscillate.

(e) Incorrect adjustment of compensating condenser. The correct

procedure for adjust-

ing the compensating condenser is given in Part II,

Section 10.

[10] ADJUSTMENT OF R. F. COMPENSATING

CONDENSER

The R.F. compensating condenser in the No. 311 receiver is

provided to allow adjustment

of the receiver to compensate for variations of tube

characteristics and thereby allow the re-

ceiver to function in its most sensitive condition.

Before readjusting this condenser, the

Radiotrons should be interchanged and satisfactory operation

secured by this means if pos-

sible.

The interchanging of tubes should be made with the idea

of getting a tube in socket

No. 2 that will not go into oscillation and gives the loudest

signal on a weak station.

satisfactory sensitivity cannot be secured by this means an

adjustment of the compensating

condenser may be made as follows :

(a) Put receiver in operation in usual manner and tune in a

station preferably at the

middle or upper wave lengths.

Page 71

(b) Locate the compensating condenser adjusting screw which is accessible through the

hole near the center at the back of the receiver cabinet.

the right until the set goes into oscillation.

Then turn the screw to the left until

all oscillation and howl is eliminated with the volume control at maximum.

some cases interchanging the tubes in the R.F. stages

will facilitate this adjustment.

(d) Tune in stations with maximum volume and note if the receiver goes into oscilla-

tion at any wavelength.

If it does, turn the screw still further to the left.

(e) When the adjusting screw has been turned to the right as far as possible without

oscillation occurring at any wavelength, the correct adjustment has been found for

best sensitivity.

*t;);'

Figure 9-Internal connections of output con-

denser and choke and filter condensers

[11] DISTORTED REPRODUCTION

Under normal conditions the No. 311 receiver will deliver a strong signal of good quality

to the loudspeaker.

The high sensitivity of this set makes it undesirable to operate the set at

full volume when receiving from a nearby broadcasting station.

The volume control should

be adjusted to secure best quality, with the desired volume.

If the loudspeaker reproduction is

poor, test the loudspeaker output from the

receiver. A pair of phones or loudspeaker of known

quality may be used for this purpose.

If the loudspeaker is 0. K. poor quality or distortion

may be due to any of the following causes:

(a) Defective Radiotrons.

Though the receiver may be in operating condition a defect-

ive Radiotron in any stage will cause distortion.

This is especially true of the

detector, 1st and 2nd audio stages and the rectifier tube.

(b) High or low plate and grid voltages from the Socket Power Unit.

The cause may

be a defective Radiotron UX-280 or resistance unit.

Replace the Radiotron

,may

with one of known quality and check the various resistances for a possible

short

or open.

The cause of noisy operation and intermittent signals with periods of hum or no recep-

tion may be traced in the following manner :

(a) Disconnect the antenna and ground leads.

If reception becomes quiet and sig-

nals from local stations, though weak, are received the trouble is in the antenna

system, or is caused by nearby interfering electrical apparatus.

In the first case

repair the antenna system and in the second case place radio frequency chokes on

any offending nearby apparatus. The location

of interfering electrical machinery

will require patience, skill and experimenting.

(b) If disconnecting the antenna and ground does not eliminate the noise, the trouble

is in the receiver.

A defective tube, one having poorly welded elements 'will cause

a disturbance of this kind, and this point

should be checked by interchanging the

Radiotrons in the receiver with others of the same type.

If it is definitely established

Page 72

that the Radiotrons are O.K. the Radiotron prongs and the socket contacts should

be examined for dirt or poor contact.

The volume control should be examined for

poor contact between the contact arm and the resistor strip.

[12] PILOT LAMP

The No. 311 set is equipped with a small pilot lamp operating from the UX-171A filament

winding.

Its purpose is to illuminate the tuning dial and act as a current supply indicator.

The latter use is quite important because the time required for Radiotron UY-227 to develop normal operation, which is approximately 30 seconds, can be checked.

The pilot lamp is mounted on a small lever that can be pulled clear of the dial for

inserting the lamp and then pushed in place to give proper illumination to the translucent

dial.

If the lamp is not in its proper place,

insufficient illumination of the dial will be

experienced.

[13] FILTER CONDENSER, AND OUTPUT CONDENSER AND CHOKE

The output choke and condenser and the two filtering condensers are located in one con-

tainer in the S.P.U.

Figure 9 shows the internal connections.

The procedure for testing

this unit is to "click test" the choke for an open, and charge and discharge the condensers

individually by shorting their terminals with a screwdriver. A condenser that will not retain

UX-280

POWER

TRANSFORMER

OUTPUT CONDENSER

AND CHOKE

AND

FILTER.CONDENSERS

FILTER

REACTORS

Figure 10-Diagram showing location of Radiotron socket contacts

its charge is defective.

Approximately 200 volts D.C. should be used when making this test.

An open output condenser or an open or shorted choke will cause weak and distorted

reproduction.

A defective filter condenser is

indicated by excessively hot plates, possibly

showing color, in Radiotron UX-280.

PART III -ELECTRICAL TESTS

[1] VOLTAGE READINGS

Voltage readings of the No. 311 set may best be checked at individual tube sockets with

a Weston Model 537, Type 2, test set or others giving similar readings.

The following read-

ings taken at the sockets are correct when connected to a 120 -volt A.C. line.

There is no

voltage between the detector heater and cathode in this receiver.

[2] VOLTAGE SUPPLY SYSTEM

It is well to understand the various voltage supply systems incorporated as they differ

somewhat from the systems normally used. Generally speaking, the No. 311 receiver uses what is known as the series resistance method of obtaining its various voltages.

This series arrange-

ment makes it possible to use small filter condensers.

Figure 11 shows the schematic circuit.

The grid bias voltages are obtained by using the drop across a resistance connected in the

plate return lead.

With this arrangement the correct grid or plate voltage is dependent on the Radiotrons

being in good condition.

A low emission tube will cause the voltage to rise on all tubes.

Page 73

Tube No.

1 2

5 6

Filament to

Grid Volts

9 9

Filament or

Cathode to Plate

Volts

130

130 130

130 135

Plate Current

Milliamperes

4.5

2.0

4.5

17.0

Filament

Voltage

1.5

2.5

1.5

5.0

FILTER

REACTORS

OUTPUT

CHOKE

.5 MFD.

UX-171-A

-\\

- OUTPUT

1 MFD.

Figure 11-Schematic circuit diagram of voltage supply system

is important to note that when interchanging Radiotrons all tubes should be in their respective sockets before turning "on" the current supply.

[3] CONTINUITY TESTS

The following tests will show complete continuity for the receiver assembly (Figure 12)

and the Socket Power Unit (Figure 13).

Disconnect the antenna and ground leads and

the A.C. supply cord at its outlet.

A pair of headphones with at least 4Y2 volts in series or a voltmeter with sufficient volt-

age to give a full scale deflection when connected directly across the battery terminals should

be used in making these tests.

The receiver sockets, numbers and lugs used in these tests

are shown in Figure 10.

The S.P.U. terminals are shown in Figure 13.

PART IV -MAKING REPLACEMENTS

The various assemblies and parts of the No. 311 receiver are easy of access and replace-

ments can be made quickly.

[1] REPLACING VOLUME CONTROL

The following procedure should be used when replacing the volume control.

(a) Remove the eight screws that hold the receiver assembly and S.P.U. to the bottom

of the cabinet.

(b) Remove the metal lid and release the screw holding the ground lead to the back

of the cabinet.

All the knobs are of the push type and can be

removed by simply pulling off.

Page 74

ANTENNA

GROUND

VOLUME

CONTROL

BLACK

R. F. COIL ASSEMBLY ------

A. F.

COND.

DET. PLATE

RESISTOR -A'

GROUND

TO FRAME

GRID COND

A.F.

BY-PASS

COND.

BLACK

`BLACK

GRID

LEAK

CABLE

BUS

BUS_

.4 ",1'

11111

DETECTOR TRIMMING CONDENSER -4r'

BUS

R. F. COMPENSATING CONDENSER

DETECTOR SERIES

/RESISTOR

BY-PASS

CONDENSERS

BUS

FFFF

BLACK=,

BLACK

BLACKWITH..YELLOW.TRACER

BLACK.WITH.-YELLOW.TRACER

BLUE

INTERNAL CONNECTIONS

2 1

`-tNak'irN

5 MFD.

.1 MFD.

LEAD CLAMP

GREENS

GREEN

'41=

RED

SLACK*WITHGREEN.TRACER

M AROON.AND.RED.

SOCKET,'

POWER UNIT

Figure 12---1Viring diagram of receiver assembly --grid leak in some models is connected

from grid of socket No. 4 to ground connection of frame instead of as shown

Page 75

RECEIVER ASSEMBLY AND S. P. U. CONTINUITY TESTS

Remove All Radiotrons and Disconnect A. C, Input Plug

Circuit

Terminals

CorrectEffect

Incorrect Effect Caused by

Grid

Antenna to ground

Antenna to G1

G2 to Gnd. G3 to Gnd.

Stator condenser No. 3 to

Gnd.

G4 to Gnd.

G5 to Gnd. G6 to Gnd.

Closed

Closed Closed Closed

(Very

Weak)

Closed Closed

Open volume control

Open volume control or contact arm

Open secondary of 1st R.F. trans-

former

Open secondary of 2d R.F. trans-

former

Open secondary of 3d R.F. trans -

former

Open grid leak or if loud, shorted

grid condenser

Open secondary of 1st A.F. trans-

former

Open secondary of 2d A.F. trans-

former

Plate

P1 to P6

P2 to P6

P3 to P6

P4 to P6

P4 to Ground

P5 to P6

P6 to either UX-280 fila-

ment contact

Closed

Open primary of 1st R.F. trans-

former, 1,600 ohm resistor or out-

put choke

Open primary of 2d R.F. trans-

former,

concentrated

primary

coil, 1600 ohm resistor or output

choke

Open primary of 3d R.F. concen-

trated primary coil, 1600 ohm

resistor or output choke

Open primary of 1st A.F. trans-

former, 30,000 ohms resistor or

output choke

Open primary of 1st A.F. trans-

former or 15,000 ohm 'plate re-

sistor

Open primary of 2d A.F. trans-

former, 1600 ohm resistor or out-

put choke

Open output choke, filter reactor

UX-280 filamerit winding

Filament

Across filament contacts of

sockets

Nos. 1,

2, 3

and 5*

Across heater contacts of

socket No. 4*

Across filament contacts of

socket No. 6*

Closed

Open UX-226 filament winding of

power transformer and center

tapped resistor or wiring

Open UY-227 heater winding of

power transformer and center

tapped resistor or wiring

Open UX-171A filament winding

of power transformer and center

tapped resistor or wiring

* In making these tests if the filaments light, the center tapped resistances should be

checked by releasing all connections to them.

An open center tapped resistor is generally

indicated by excessive hum.

Page 76

BLOCK

vy..001NAIEO.VLCER

TO PILOT LAMP

GREEN

OBEEN

4..,BLAC KWITII.YELLOW.TRA

CfR

4.111.ACK-W1714,1ELLOW.TRACER

BLUE

.0E.RED

.11IBLACK.WITIOGREEN.TRACER

4.....MAROON.AND.RED

RECEIVER.

ASSEMBLY

CIMB5LACK

GROUND TO METAL CABINET

OPERATING

-SPLICES

REVERSE THESE LEADS

FOR 110 -VOLT OPERATION

BLACK.ANDRED

110 -VOLT TAPED LEAD

TO POWER TRANSFORMER\

41.7)

;c::::::tD1

c,'

PC E li

ip.

a Y.o

In.1_il

CENTER

TAPPED

RESISTORS;

--a

1111

,,,,

TO FILTER

REACTOR.

-01

GRID AND PLATE

..;

RESISTANCE UNIT. 4,

''' GROUND TO ':"

.13LAC

111'

FRAME

LUE...

I, ,

4 .

: 1111!! 1

111

Ili

BLACK WITH

YELLOW

7GTE

%*-

TRACER'

)0V,

BLUE

BLACK

AP -

G%.

A OUTPUT

JACKS

,,,

.2161

.E;,

"- '

....

<2:NF

131.110( MTH

GREEN TRACER.

-1-

..f

.s MFi1,

UX-280 SOCKET

BLACK

RED

MAROON.AND.RED

........4.

CONDENSER AND CHOKE

AND

FILTER. CONDENSERS ---

Figure 13-Wiring diagram of socket power unit

RECEIVER ASSEMBLY AND S.P.U. CONTINUITY TESTS-Con'd

Circuit

Terminals

Correct

Effect

Closed

Incorrect Effect Caused by

Across

UX-280

filament

contacts

Open UX-280 filament winding

Across A.C. input plug

with

operating

switch

Closed

Open primary of power transformer

"On"

S.P.U.

G to P of UX-280 socket

Closed

Open high voltage winding of power

transformer

Either F5 to Ground

Closed

Open 440 -ohm bias resistance

Either F6 to Ground

Closed Open 1900 -ohm bias resistance

P6 to one output pin ter-

Open

Shorted .5 mfd. output condenser

minal (next to rear of

cabinet)

Page 77

(d) Remove the collar that holds the switch to the front of the cabinet.

The switch

should now be pulled clear of the cabinet.

(e) Pull the input A.C. cord through the large hole in the bottom of the cabinet and

let it hang over the cabinet side so that it will be clear when the receiver assembly

and S.P.U. are removed.

Pull the antenna and ground leads clear.

(f)

Grasping the receiver assembly by the tuning condenser assembly and the S.P.U.

by the power transformer or filter re actor, lift the two assemblies clear of the cabi-

net.

The S.P.U. can be lifted straight up, but the receiver assembly must first be

pulled back slightly so the volume control and tuning control clear the front of the

cabinet.

Place the two assemblies on a suitable support for work.

(g) Unsolder the leads to the volume control.

(h) Remove the two screws that hold the volume control to the metal chassis.

It may

now be removed and the new one fastened in place.

The connections should be

soldered to the new volume control.

These connections are shown in Figure 12.

(i)

The receiver is now reassembled in the reverse manner of that already given.

[2] REPLACING RADIO FREQUENCY COILS

The three radio frequency transformers together with small fixed condensers across the

concentrated primary coils and R.F. compensating and detector trimming condensers are

mounted on one strip and must be replaced as a unit.

The following procedure is used:

(a) Remove the chassis assembly from the cabinet as described in Part IV, Section 1.

(b) Unsolder all connections to the three transformers. (c) Remove the three screws that hold the mounting strip to the metal chassis.

The

entire assembly can now be removed.

The new assembly is placed in the position

occupied by the old one.

(d) Replace the screws that hold the mounting strip to the metal chassis.

(e) Replace and resolder all leads to the three transformers.

These connections are

shown in Figure 12.

When making this replacement be careful not to disturb the

two condensers connected across the c oncentrated

coils.

Placing these condensers

closer to the coils than their normal position will affect the inductance of the coil

with a resulting decrease of sensitivity.

(f) Return chassis assembly to cabinet and replace all screws and knobs.

Adjust the

compensating condenser to the correct position as indicated in Part II, Section 10.

Also adjust the detector trimming condenser as described in Part II, Section 5.

[3] REPLACING RADIOTRON GANG SOCKETS

The Radiotron sockets of the No. 311 receiver are of the gang variety, using one detector

socket; two A.F. socket strips, and one three -gang socket strip for the radio frequency ampli-

fying tubes.

There is a small Bakelite shield placed over all sockets.

This shield is supplied

separately and does not come with the socket.

The sockets are riveted to the metal chassis.

To replace them, drill out the old rivets and use screws, nuts and lock washers for securing

the new sockets. A step by step procedure follows :

(a) Remove chassis assembly from cabinet as described in Part IV, Section 1.

(b) Remove all leads to the terminals of the sockets.

In some cases

it may be necessary to loosen the R.F. transformer assembly in order to slip the

socket strips out.

(d) The socket assembly is now removed and the new one placed in the position occupied

by the old one.

(e) Fasten new socket in place by using small round head machine screws, nuts and

lock washers in place of the rivets previously removed.

(f)

Replace connections as indicated in Figure 12 for the correct socket connections.

(g) Return chassis to cabinet.

[4] REPLACING MAIN TUNING CONDENSERS AND DRIVE

The main tuning condensers and the driving mechanism are replaced as one complete

unit.

The step by step procedure follows:

Page 78

(a) Remove chassis assembly from housing as described in Part IV, Section 1.

(b) Unsolder four connections to condensers.

that holds the assembly to the frame.

(d) The assembly may now be removed and the new assembly placed in the position

occupied by the old one.

Be sure and connect the ground wire previously con-

nected under the nut and washer to one screw.

(e) Replace the three screws, nuts and lock washers and resolder the leads. (f) Replace chassis assembly in cabinet.

[5] REPLACING BY-PASS CONDENSER

This condenser, located on the under side of the chassis frame is held in place by four

metal tabs that are a part of the condenser case and are bent over on the upper side of the

Figure 14-Gang tuning condenser drive

mechanism and cable

metal chassis.

A step by step procedure for making this replacement follows:

(a) Remove chassis from cabinet as described in Part IV, Section 1.

(b) Remove tuning condenser assembly from chassis

as described in Part IV, Section 4.

(d) The four tabs holding the condenser to the chassis may now be bent up with a

screw -driver and the old condenser replaced by the new one. Insert the tabs in the

holes and bend them over on the upper side of the chassis assembly.

Resolder the

leads and resistors to their correct terminals.

The connections are shown in Fig-

ure 12.

(e) Replace the tuning condenser assembly as described in Part IV, Section 4.

(f) Return chassis assembly to cabinet in reverse order of that used to remove it.

[6] REPLACING AUDIO FREQUENCY TRANSFORMERS

The audio transformers are built together in one unit. In making a replacement the

following procedure should be used:

Page 79

(a) Remove chassis from cabinet as described in Part IV, Section 1.

(b) Unsolder all leads to the audio transformers.

chassis frame and remove it.

(d) Place the new transformer in the position occupied by the old one, bend over the

tabs and resolder all connections.

The correct connections are shown in Figure 12.

(e) Replace chassis in cabinet in the reverse order of that used to remove it.

[7] REPLACING CONDENSER DRIVE CABLE

The condenser drive cable is of rugged fishline and should give good service.

If replace-

ment becomes necessary proceed as follows:

(a) Remove the chassis from the cabinet as described in Part IV, Section

1. Place

chassis on table with controls to the front.

(b) Remove the old cable from large drum and grooved drums completely.

the old one.

(d) Re -assemble the receiver in the reverse manner of that used to disassemble it.

[8] REPLACING TUNING DIAL

After considerable use a tuning dial may become dirty or illegible and a new scale desired.

A step by step procedure for making replacement follows:

(a) Open lid of cabinet.

(b) Turn dial so that the small clamp that holds the dial in place is on top.

(d) Replace old dial with new one and clamp in place. (e) Close lid of cabinet.

[9] REPLACING FILTER CONDENSER, OUTPUT CHOKE AND

CONDENSER ASSEMBLY

The filter condensers, together with the output choke and condenser, are all contained

in one metal container and must be replaced as a unit.

The replacement procedure follows:

(a) Remove the receiver assembly and S.P.U. as described in Part IV, Section 1.

(b) Unsolder the connections to the filter condenser unit.

The

entire assembly may now be removed and the new one placed in the position occu-

pied by the old one.

(d) Clamp the assembly in place by turning the tabs over on the under side of the base.

Solder the connections as indicated in Figure 13.

(e) Return the S.P.U. to the cabinet and re -assemble in the reverse order of that used

to remove it.

[10] REPLACING EITHER POWER TRANSFORMER OR FILTER

REACTOR

The power transformer and the filter reactor are each encased in a metal container.

Either unit may be replaced in the following manner :

(a) Remove receiver assembly and S.P.U. from cabinet as described in Part IV, Sec-

tion 1.

(b) Unsolder the leads of the unit being replaced.

resistance unit in order to bend all the tabs. The particular assembly being re-

placed may now be removed and the new assembly placed in the position occupied

by the old one.

(d) The tabs on the new assembly should be bent so as to properly fasten the unit to

the S.P.U. base.

(e) Connect all the leads from the assembly to the points of connection as in Figure

13 which should be followed exactly when any S.P.U. parts are replaced.

(f) Return to cabinet in the reverse order, and connect to receiver assembly.

Page 80

SERVICE DATA CHART

Before using the following Service Data Chart, when experiencing no signals, weak sig-

nals, poor quality, noisy or intermittent reception, howling and fading, first look for defective

tubes, or a poor antenna system.

If imperfect operation is not due to these causes the "Service

Data Chart" should be consulted for further detailed causes.

Reference to Part No. and Section

No. in the "Service Notes" is also noted for further details.

Indication

Cause

Remedy

No signals

Defective operating switch

Loose volume control arm

Defective R.F. transformer

Defective A.F. transformer

Defective By-pass condenser

Defective socket power unit

Repair or replace switch

Tighten volume control arm, P. II, S. 4

Replace R.F. transformer assembly, P. IV, S. 2 Replace A.F. transformer assembly, P. IV, S. 6

Replace By-pass condenser, P. IV, S. 5

Check socket power unit by means of continuity

test and make any repairs or replacements

necessary, P. III, S. 3

Weak Signals

Compensating condenser out of ad-

justment Defective R.F. transformer Defective A.F. transformer Dirty prongs of Radiotrons

Defective By-pass condenser Defective main tuning condensers Low voltages from socket power unit

Defective socket power unit

Adjust compensating condenser correctly, P. II,

S. 10

Replace R.F. transformer assembly, P. IV, S.

Replace A.F. transformer assembly, P. IV, S. 6

Clean prongs with fine sandpaper, P. II, S. 3

Replace defective By-pass condenser, P. IV, S. 5

Replace defective tuning condensers, P. IV, S. 4

Check socket power unit voltages with high re-

sistance D.C. voltmeter and A.C. voltmeter,

P. III, S. 1

Check socket power unit by means of continuity

test

make any repairs or replacements

necessary, P. III, S. 3

Poor Quality

Defective A.F. transformer

Defective By-pass condenser

Dirty prongs on Radiotrons

Defective output condenser or choke

Replace A.F. transformer assembly, P. IV, S. 6

Replace defective By-pass condenser, P. IV, S. 5

Clean prongs with fine sandpaper, P. II, S. 3

Replace output condenser and choke, P. IV, S. 8

Howling

Compensating condenser out of ad-

justment

Defect in audio system

Open grid circuit in any stage

Receiver in oscillation

Adjust compensating condenser correctly, P. II,

S. 10

Check and repair any defect, P. III, S. 3 Check circuit and repair defect

Correct cause of oscillation, P. II, S. 9

Excessive Hum

Defective center tapped resistance

unit

Socket plug position

Line voltage low

Defective filter condenser

Replace defective resistance unit

Reverse socket plug, P. I, S. 4

Reconnect transformer for low line voltage, P. I,

S. 5

Replace defective condenser

Radiotrons fail

to light

Operating switch not "On"

Defective operating switch Defective input A.C. cord

Defective power transformer

No A.C. line voltage

Turn operating switch "On"

Replace operating switch

Repair or replace A.C. input cord

Replace power transformer, P. IV, S. 10 Turn A.C. line voltage "On"

Page 81

PART V

No. 311 Receiver Replacement Parts

No.

Description

*Price

No.

RECEIVER ASSEMBLIES

2006 Radiotron socket contact-Package of 10

$0.50

2010 Condenser-Fixed condenser 160 mmfd. con-

nected across concentrated coil and second.

ary of 1st audio transformer and used as

grid

condenser ...

Description

*Price

2240 Resistor-Series

resistor for detector plate

supply --30,000 ohms-Carbon type

$0.70

2349 Knob-Station selector-Push-on

type with

holding spring to fit

1/4" shaft .

2394 Shield-Insulating

shield (black)

for UX

.50

Radiotron socket ..

2011 Grid leak -4 Megohm-Carbon type

.70

2012 Condenser --Fixed condenser .0012 mfd. con-

nected to primary of 1st audio transformer

2027 Radiotron socket-UY-227 type

2032 Antenna and ground leads -5 feet long-One

set .

switch knob-Push-on pendant type with

.60

bolding spring-To fit 14" shaft . .50

.60

.50

2513 Cord-Gang condenser drive cord . .50

2514 Knob-Volume control or rotary operating

2515 Cable-Laced

wiring cable from receiver

.50

chassis to S. P U

1.50

* These prices are subject to change at our option without notice.

Page 82

No. 311 Receiver Replacement Parts

No.

Description

*Price

No.

Description

*Price

RECEIVER ASSEMBLIES-Continued

5995 Scale-Translucent

dial

scale with

spring

clamp-Package of 5

$1 80

5662 Sockets -3 -Gang UX Radiotron sockets

$0.75

5996 Condenser-Tapped-Comprising one 1/2 and

5663 Sockets -2 -Gang UX Radiotron sockets

.55

three .1 mfd. condensers-Has one terminal

board containing 1 terminal and a second

5667 Transformers -2 -Audio transformers-lst and

2d stage-In metal container

. . .

6.75

terminal board containing 4 terminals

3.00

5807 Condenser-Detector trimming condenser

1.20

8463 R. F. Coil Assembly-Comprising 3 coils, 2

fixed condensers, 2 concentrated coils and

5818 Resistor -14300 ohms-Detector plate supply

2 adjustable condensers mounted on a metal

resistor

strip

5 40

5843 Condenser-R. F. compensating condenser

1.20

5901 Volume control -2000 ohms -1/2" shaft-For

8464 Condensers -3 -Gang tuning condensers with

drive, cord, pilot lamp socket and bracket

pushon type knob

1 95

-Less scale, scale clamp and lamp

. .

11.25

These prices are subject to change at our option without notice.

Page 83

No. 311 Receiver Replacement Parts

No.

Description

*Price

No.

Description

*Price

S. P. U. ASSEMBLIES 2518 Switch-Rotary operating switch with two 8"

leads

$1 10

2242 Resistance Unit-3940ohm resistor tapped at

1600, 1900 and 440 ohms-Has 2 mounting

8333 Output choke and condenser and 2 filter con

brackets and 5 soldering terminals-Plate

densers in metal container

. . . .

7.40

and grid supply (Not illustrated)

. . $0.80

8335 Power Transformer-60cycle, 110

volts-In

2243 Resistance

Unit -3

Resistance

units mid-

tapped-Mounted on S. P. U. base under

power transformer (Not illustrated)

. . 1.25

metal container

. . .

8336 Choke Coil in metal container .

12.90

10.05

2267 Socket-Single UX Radiotron socket without

8340 Power Transformer-25cycle, 110 volts-In

protective shield

metal container (Not illustrated)

. 18.75

* These prices are subject to change at our option without notice.

Page 84

1.D.2q-5

Grayb

QUALITY

Printed in U. S. A.

R 52

Page 85

GRAYBAR

Grayb

340

Service Notes and

------------.

Replacement

RADIO

Parts

ELECTRIC

SUCCESSOR

COMPANY

10 Western Electric SUPPLY

DEPARTMENT

Page 86

Page 87

CONTENTS

Page

Introduction

Service Data Chart

PART I -INSTALLATION

Page Knobs

Antenna (Outdoor Type)

Antenna (Indoor Type)

Ground

Radiotrons

Line Switch

Receiving Loud Local Stations

Distortion Due to Loud Signals

Pick -Up from Long Wave High Power Sta-

tions

Location of Receiver in Room

Shipping Bracket for Reproducer Unit

PART II -SERVICE DATA

Antenna System Failures

Radiotron Sockets

Radiotron Prongs

Loose Volume Control

Adjustment for Slack Drum Control

Broken Condenser Drive Cable

Hum

Distortion in Reproducer

Low Volume and Weak Signals

Audio Howl

Distorted Reproduction

Adjustment of Oscillator Trimming

Condensers

PART III -

Adjustment of R.F. Compensating Condenser

Adjustment of I.F. Transformers

13 13

Output Condenser and Choke, Output Trans-

former and Filter Condensers

Voltage Supply System

Voltage Readings

Checking Resistance Values

Testing Disc Rectifier

Reproducer Unit 21

Centering Cone of Reproducer Unit

Graybar 340 Continuity Tests 22

15 Voltage Readings at Radiotron Sockets 27

MAKING REPLACEMENTS

Replacing the Volume Control

Replacing R.F. Transformer and

Oscillator

Assembly

Replacing Radiotron Gang Sockets

Replacing Main Tuning Condensers and Drive

Replacing By -Pass Condensers

Replacing the Audio Transformer

Replacing Condenser Drive Cable

Replacing Dial Scales

Replacing Power Cable

Replacing Intermediate Transformers

28 Replacing Tapped Resistance Unit in Receiver

Assembly 32

Replacing Cone of Reproducer Unit 33

Replacing Filter Condensers

and By -Pass

Condensers 33

Replacing Power Transformer or Filter

Reactor

Replacing Terminal Strip 34

Replacing Miscellaneous Parts in S.P.U. 34

Replacing Coupling Unit 35

Replacing Condenser Bank of Field Supply

Unit

Replacing Rectifier Stack

PART IV -REPLACEMENT PARTS

Receiver Parts

36-37

Field Supply Unit

Socket Power Unit

Reproducer Assembly 8" Cone

ILLUSTRATIONS

Graybar 340

Rear Interior View of Graybar 340

Socket Power Unit Field Supply Unit

Radiotron Sequence

Schematic Circuit Diagram of Graybar 340

Long Wave Interference Filter

Dimensions of Non -Metallic Screw Driver

Adjusting Trimming and Compensating Con-

densers

180 K.C. Test Oscillator

Location of Neutralizing, Trimming, Tuning

and Compensating Condensers

Adjusting Neutralizing Condensers

Internal Connections of I.F. Transformers

Cable Connections to S.P.U. and Field Supply

Terminal Strips

1 Schematic Circuit of Voltage Supply System

Internal Connections of

Filter and By -Pass

Condensers

Internal Connections of Coupling Unit 20

Internal Connections of Condenser Bank in

Field Supply Unit

Centering Cone 21

Location of Radiotron Sockets and Other

Parts 22

S.P.U. Continuity Wiring 23

Receiver Continuity Wiring

Field Supply Continuity Wiring

Receiver Sub -Chassis Assembly 28

Removing Receiver from Cabinet

Removing Field Supply Unit from Cabinet

10 12

Page 88

# #

It' #

##:

# 4

irr

. ),

GRAYBAR 340

Figure 1-Rear interior view of Graybar 340, showing Receiver

Chassis at top, Reproducer below shelf and S.P.U. at bottom left

and Field Supply Unit at bottom right

Page 89

GRAYBAR 340

(105-125 Volts. 50-60 Cycle A. C.)

SERVICE NOTES

INTRODUCTION

Graybar 340 is an eight -tube socket powered radio receiver employing seven UY-227

Radiotrons and one UX-171A Radiotron. One Radiotron UX-280 is used in a socket power

unit for supplying all grid and plate voltages.

A dry disc type rectifier furnishes direct

current of the correct voltage to the field of the reproducer unit.

Graybar 340 is

fundamentally

a console cabinet model of Graybar 330, utilizing a new type dynamic reproducer and having

such circuit changes as are necessary for use with a speaker of this type. Figure 1 illustrates

a rear view showing the principal parts.

Figure 2 illustrates the socket power unit and Figure

3 shows the field supply unit.

FILTER AND BY-PASS

FILTER

POWER

CONDENSERS

REACTORS

TRANSFORMER

LINE VOLTAGE

ADJUSTMENT

SWITCH

TERMINAL

STRIP

INPUT PLUG

TO FIELD

TO SERIES

SUPPLY UNIT

TAPPED RECEPTACLE

Figure 2

Socket

poi( cr unit

Graybar 310 is designed to operate on aLernating current of 105 to 125 volts, 50 to 60

cycles, such as is used for house lighting. Connection to D. C. lines or to A. C. lines of

different rating may damage the receiver or the Radiotrons.

Graybar 340 is also made in models designed for 105-125 volts, 25-40 cycles A. C. opera-

tion.

In this model the power transformer is

different from that used in the 50-60 cycle

models and the condenser shunted across the output of the disc rectifier has a capacity of 6 mfd.

instead of 4 mfd., as used in the 50-60 cycle sets.

All other parts are identical in both models

and the Service Notes apply to each equally well.

Page 90

The following circuit characteristics are incorporated in Graybar 340:

(a) As already stated, Graybar 340 uses seven Radiotrons UY-227 and one Radiotron UX-

171A connected up in an eight -tube super -heterodyne circuit with a UX-280 in the

S. P. U. for grid and plate supply.

(b) A new type dynamic reproducer unit is used, the field current for this unit being

obtained from a dry disc type of rectifier, thus keeping the load on the Radiotron

UX-280 at a minimum value.

heterodyne detector, two intermediate R.F. stages, an oscillator, a second detector and

a power amplifier.

COUPLING

UNIT

TERMINAL

STRIP

CONDENSER BANK

Figure 3-Field supply unit

(d) The second detector, operated at 160 volts plate potential with grid bias, changes the

radio frequency current of the intermediate stages into audio frequency current. This

gives sufficient output to operate the power tube directly from the second detector,

thus eliminating any distortion that might be present if an intermediate audio stage

were used.

(e) The volume control regulates the grid bias on all radio and intermediate frequency

amplifying stages, giving a positive control of volume, even on nearby local stations,

without distortion.

(f) By means of a baffle board mounted several inches from the front of the cabinet, all

cabinet resonance effects are eliminated, thus making the output even and natural.

Figure 4 illustrates the sequence of the Radiotrons in the receiver, omitting Radiotron

UX-280 in the socket power unit.

From right to left, when facing the front of the receiver,

the Radiotron sequence is as follows:

Radiotron No. 1

is an untuned stage of radio frequency amplification.

It is coupled

directly to the antenna and ground across a 2000 -ohm resistance and functions as a coupling tube to the antenna system.

Radiotron No. 2 is a stage of tuned radio frequency amplification. It is tuned by means

of the first of the gang condensers.

DISC RECTIFIER

Page 91

Radiotron No. 3 is the tuned heterodyne detector.

It is tuned by the center of the gang

condensers.

Radiotrons No. 4 and No. 5 are the first and second intermediate frequency stages. These

stages are tuned to a frequency of 180 K.C., giving ample distance between the two peaks of the

oscillator to eliminate any possibility of stations coming in at more than one point on the tun-

ing dial.

Radiotron No. 6 is the oscillator.

It is tuned by the third of the gang condensers. Two

trimming condensers are provided at the rear of the receiver assembly for adjusting the oscil-

lator circuit to keep the beat note at the correct frequency for the intermediate stages.

Radiotron No. 7 is the second detector.

It operates at a plate potential of 160 volts with

the proper grid bias and does not use a grid leak or condenser.

Its output is

sufficient to

drive the power amplifier.

Radiotron No. 8 is the power amplifier. A choke and condenser arrangement couples this

tube to the step-down transformer that matches the impedance of this output circuit to that of

the cone coil of the reproducer unit.

This arrangement gives a quality of reproduction not

obtainable with the use of an output transformer alone.

LOUDSPEAKER

TUNED 13I

:TUNED

DET.

iR.F.

RADIO FREQUENCY CURRENT

OSCILLATOR CURRENT

R.F.CURRENT IN INTERMEDIATE STAGES

A. F. CURRENT

Figure 4-Radiotron sequence

ANT.

STAGE

These various principles incorporated in Graybar 340 and illustrated in the schematic

.circuit Figure 5, provides a radio receiver of advanced design, excellent performance and good

tone quality.

PART I-INSTALLATION

[1] ANTENNA (Outdoor Type)

Due to the high sensitivity of Graybar 340 the antenna length need only be approximately

25 feet.

It should be erected as high as possible and be removed from all obstructions.

The

lead-in should be a continuation of the antenna itself, thus avoiding all splices which might

introduce additional resistance and, in time, corrode sufficiently to seriously affect reception.

If it is absolutely necessary to splice the lead-in to the antenna the joint must be carefully

soldered to insure a good electrical contact.

Clean off all excess flux and tape the connection,

to protect it from the oxidation effects of the atmosphere.

High-grade glass or porcelain insulator supports are required, and at no point should the

antenna or lead-in wire come in contact with any part of the building. Bring the lead-in wire

from the outside through a porcelain tube insulator to the inside of the house for connection

to the receiver.

The antenna should not cross either over or under any electric light, traction, or power

line and should be at right angles to these lines and other antennas.

An outdoor antenna

should be protected by means of an approved lightning arrester, in accordance with the re-

quirements of the National Fire Underwriters' Code.

Page 92

UY-227

INPUT

UY-2/7

R F

S=T.

NED

UY-221

IS] DET

.UY-227

05C

S.=>

REPRODUCER

OPERATING

SWITCH

105-125 VOLTS

50.60- A C

DISC TYPE

RECTIFIER

FIELD

SUPPLY

TERMINAL

STRIP

20 03

4 MID

.11.110.

.114FD

----448

OUTPUT

TRANSFORMER

,Q00-0(1-0,

'0000001

5 MN/

OUTPUT

COND

Sco-H--'

UY-227

V 10

IUQ.Of

OUTPUT

'CHOKE

POWER

TRANSFORMER

.5 WO

1000i

UY-227

2ND I. F

UV -22/

2t*DET

35 MFD

35II

MFD

VOLUME

CONTROL

UX-171-A

PWR. AMP

PILOT

LAMP

NOT

USED)

TERMINAL

STRIP

FILTER _

REACTOR*:-.'

UX-280

ounn0000kooDooupoo

1.1010T

I I I 1111111i I I

I I I

I I I I I I I I

I I I I I

OLD SUPPLY TERMINAL STRIP

LINE VOLTAGE

-ADJUSTMENT

SWITCH

Figure 5-Schematic circuit diagram of Graybar 340

Page 93

[2) ANTENNA (Indoor Type)

Where the installation of an outdoor antenna is not practical, satisfactory results may

generally be obtained by using an indoor antenna of about 25 feet of insulated wire strung

around the picture moulding or placed under a rug.

In buildings where metal lathing is em-

ployed, satisfactory results are not always possible with this type of antenna. However, due

to its sensitivity, Graybar 340 will generally give entirely satisfactory reception with an indoor

antenna.

[3) GROUND

A good ground is quite as important as a good antenna.

No specific recommendations

can be given in this matter as conditions vary in different locations.

Water and steam pipes

usually make good grounds.

Gas pipes usually make poor grounds and, as a rule, are to be

avoided. If neither water nor steam pipes are available, a pipe or metal rod may be driven

into the ground to a depth of several feet.

The success of this type of ground depends upon

the moisture present in the soil.

The ground lead should be connected by means of an

approved ground clamp to a section of pipe that has been scraped and thoroughly cleaned.

The connection should be inspected from time to time to make certain that a clean and tight

electrical contact exists between the clamp and pipe. The service man should experiment with various grounds, and employ the one giving the best results.

A spark will occur if the power supply is "on" when making the ground connection.

This action is normal, being caused by the discharge of one of the .1 mfd. condensers con-

nected across the power input to the disc rectifier.

No current is consumed as no load is

being drawn through the condenser.

[4) RADIOTRONS

A guide shield is provided on all the receiver Radiotron sockets to facilitate the insertion

of the Radiotrons.

The seven Radiotrons UY-227 are inserted in the five -contact sockets.

The

Radiotron UX-171A is placed in the four -contact socket in the receiver assembly, and the

Radiotron UX-280 is placed in the socket power unit.

In placing Graybar 340 into operation, if no signals are heard when tuning to a station

known to be broadcasting, examine the Radiotrons.

Possibly one Radiotron has been dam-

aged in transit.

Interchanging with one or more of the same type known to be in operating

condition will isolate the damaged one.

Socket No. 2 (Figure 4), the tuned R.F. stage,

is the most critical for selection of the

Radiotrons.

Place in this socket the tube which gives the loudest signal and does not go into

oscillation throughout the tuning range.

If no tube is found that will not oscillate, a slight

readjustment of the R.F. compensating condenser may be necessary, as described in Part II,

Section 13.

Other stages somewhat critical are the oscillator and second detector, sockets No. 6 and

No. 7, respectively.

The remaining tubes should be interchanged until a tube is found for the

oscillator that gives the loudest signal on a given station.

The second detector Radiotron

should be selected for its ability to handle large volume.

Select the tube for this socket that

will permit the volume control to be advanced and give the greatest output without overloading.

[5) LINE SWITCH

A two-way switch is provided in the S.P.U. for adjustment to line voltages.

A shield

over the terminal strip holds this switch in the 120 -volt position.

Unless it is definitely known

that the line is always below 115 volts the switch should be left in its original position.

It is a

good plan to leave this switch at the 120 -volt position on all lines unless unsatisfactory opera-

tion is experienced.

If the switch is set at the 110 -volt position on supply lines exceeding 115

volts the Radiotrons in the receiver will be damaged.

[6) KNOBS

Graybar 340 uses an improved type of push knob on the station selector and volume con-

trol shafts.

This knob is removed by simply pulling it off the shaft, and replaced by pushing it

on. Very little trouble should be

experienced, as no setscrews or other parts that might give

trouble are used.

Page 94

When placing this knob on its shaft care must be exercised not to push it tight against

the washer between the knob and cabinet, as then it will bind.

Sometimes in handling new

sets the knob will have become pushed against the washer and bind.

The remedy is merely

to pull the knob out until it does not bind.

[73 RECEIVING LOUD LOCAL STATIONS

If excess volume control adjustment is used on local stations the signal will apparently

have two peaks on the tuning dial.

A further advance of the volume control will decrease

the volume rather than increase it.

This is entirely normal, and is caused by tube overloading.

The correct method of tuning Graybar 340 on local stations is to reduce the volume control to

the position where the station will be received at only one position on the station selector dial, and then adjust the volume control for the desired volume.

On some stations when tuned in with excessive volume a howl may be experienced.

The

remedy is to reduce the volume control until the howl disappears.

This tuning procedure should be explained to the set owner when an installation is made.

ANTENNA

Q GROUND

TO GROUND

AND GROUND

BINDING POST

GRAYBAR 300

COUPLING COILS

Figure 6-Long wave interference filter

[8) DISTORTION DUE TO LOUD SIGNALS

In some localities extremely close to powerful broadcasting stations, reproduction may

be distorted when reducing volume to a point satisfactory to the listener. When installing

a set, determine by a listening test whether this condition exists or not and apply the follow-

ing remedy if the reproduction is distorted.

Procure a single -pole single -throw switch (any type will do) and connect it in series with

the antenna lead of the receiver. The switch may be located either inside or outside the

cabinet in any convenient position.

Opening the

switch

will disconnect

the

antenna and

allow satisfactory reception on signals that would otherwise be distorted. The switch should

be closed for reception from other stations.

[9) PICK-UP FROM LONG WAVE HIGH POWER

CODE STATIONS

Should Graybar 340 be installed very close to long wave, powerful code stations, it is pos-

sible that a certain amount of pick-up and interference from them will be experienced. Trouble of this kind may be eliminated in the following manner:

(a) Procure the following equipment:

Two Graybar 300 antenna coils (Stock No. 5658).

One .0002 Mfd. fixed condenser.

(b) Connect as shown in Figure 6.

in a separate unit and placed in any convenient location. It acts as a filter, allow-

ing frequencies of the broadcast band only to reach the receiver.

TO ANTENNA

BINDING

POST

TO ANTENNA

Page 95

[10) LOCATION OF RECEIVER IN ROOM

As with other musical instruments, the location of Graybar 340 in the room should be

chosen with care.

Various positions should be tried until the most desirable reproduction is

obtained.

If this position is outside the radius of the connection cord to the A.C. outlet, an

extension cord can be used.

[11) SHIPPING BRACKET FOR REPRODUCER UNIT

Graybar 340 is shipped with a metal yoke and wooden support to hold the reproducer unit

in place during shipment.

This wooden block and the metal yoke holding it should be re-

moved when placing receiver into operation as it may resonate at audible frequencies and

affect the reproducing qualities of the set.

The front flange of the reproducer offers ample

support for the reproducer unit on all occasions except when shipping.

PART II-SERVICE DATA

[1) ANTENNA SYSTEM FAILURES

A grating noise may be caused by a poor lead-in connection to the antenna; or the

antenna touching some metallic surface, such as the edge of a tin roof, drain pipe, etc. By

disconnecting the antenna and ground leads the service man can soon determine whether the

cause of complaint is within or external to the receiver and plan his service work accordingly.

[2) RADIOTRON SOCKETS

The sockets used in Graybar 340 are a six -gang UY socket assembly, a single UY socket,

and two single UX sockets.

One of the UX sockets is used in the socket power unit and is of

a different design than that used in the receiver assembly.

The bakelite Radiotron guide shields used in the receiver assembly will prevent any pos-

sible shock from contact with high voltages in the socket when inserting the Radiotrons.

The prongs of the tubes fit into this shield opening very snugly and require only a twist until

the prongs find the correct holes into which they fit. This is especially helpful when inserting

the five -prong tubes into their sockets.

[3) RADIOTRON PRONGS

Dirty Radiotron prongs may cause noisy operation or change the resistance of the fila-

ment circuits sufficiently to cause a hum in the loudspeaker. They should therefore be cleaned

with fine sandpaper periodically to insure good contact. The use of emery cloth or steel

wool is not recommended.

Before re-inserting the Radiotrons in their sockets wipe the prongs

and base carefully to make certain that all particles of sand are removed.

If a Radiotron will not fit into a socket without considerable pressure, look for excessive

solder on one or more of the prongs. Excessive solder on the prongs may be removed with

a file or knife.

[4) LOOSE VOLUME CONTROL

A loose volume control arm may cause noisy or intermittent operation.

It should be

bent slightly so that

it makes firm contact against the resistance strip.

To do this it is

necessary to remove the chassis from the cabinet as described in Part III, Section 1.

The

volume control is then accessible.

It can be released by removing the two screws that hold

it to the metal frame.

[5) ADJUSTMENT FOR SLACK DRUM CONTROL

The main tuning condensers are controlled by a cable and drum arrangement giving a

smoothly acting vernier movement that has no back lash.

Page 96

After considerable wear or extreme changes of temperature the cable may become slack. To

take up this slack open lid of cabinet and turn the cable adjusting screw with clamp until

the cable is taut. This screw may become seated after several adjustments are made, thus allow-

ing no further tightening of the cable.

When this condition occurs it

will be necessary to

slip the cable a half turn on the grooved drum.

To make this adjustment it

is necessary

to remove the chassis from the cabinet as described in Part III,

Section

Remove the

cable adjusting screw and clamp.

This cable will then have approximately one inch slack. By

removing the tapered pin holding the front grooved drum to

its

shaft and replacing it on

the opposite side (180 degrees) the one inch slack in the cable can be taken up by using the new position of the pin for anchoring the cable.

It will be noted that the tapered pin in the

new position cannot be inserted_ as far as originally.

However, it can be inserted far enough

to lock the grooved drum to the control shaft and clear the metal housing.

If the cable

again is stretched to the maximum adjustment of the cable adjusting screw the tapered pin

can be returned to its original position and an additional half turn

slipped on the drum

which will provide for taking up all slack.

A sufficient number of grooves are provided on

the drum for this purpose.

BAKELITE,,,

STEEL BLADE

3i2"

Figure 7-Dimensions of the

non-metallic screw driver

[6) BROKEN CONDENSER DRIVE CABLE

A broken condenser drive cable can be replaced in the manner described in Part III,

Section 7.

However, if a new cable is not immediately available a temporary repair can

be made in the following manner, provided the break in the cable is not in that section that

passes over the small grooved drums.

Splice and solder the two ends together.

Splicing consists of interweaving the strands,

as with rope, and not just twisting

the cable ends together as in an electrical wiring splice.

Splicing gives greater strength and forms a smaller body on the cable.

When soldering use

plenty of flux and a small amount of solder.

Heat sufficiently so that the solder adheres to

all the strands of the cable.

Placing the splice in an alcohol or bunsen flame affords sufficient

heat and allows excess solder to drip away.

This is but a temporary repair to be used only

until a new cable can be procured.

[7) HUM

If a pronounced hum develops during operation check the following:

(a) Low emission Radiotron UX-280.

A low emission rectifying tube will cause exces-

sive hum and unsatisfactory operation.

(b) Defective center tapped resistance.

A short or open of either of these resistances

will cause a loud hum and imperfect operation of the set.

resistances may cause a certain amount of hum.

These defects will have a pro-

nounced effect on the general operation of the receiver which will be more notice-

able than the additional hum.

Check by means of the continuity test given in Part

II, Section 22.

(d) Use of Radiotron UX-171 instead of Radiotron UX-171A may cause an increase of

hum.

It is recommended that only Radiotron UX-171A be used as a power amplifier

in Graybar 340.

(e) Defective disc rectifier or condenser across output of rectifier may cause excessive

hum and faulty operation.

A check of this condition can be made as described in

Part II, Section 19.

Page 97

(f) Antenna and ground leads reversed. Reversing these leads opens the condenser center

ground connection in the field supply unit and causes hum.

A mechanical hum caused by vibration of loose laminations in the power transformer

may be corrected by removing the power transformer from the S.P.U. as described in Part

III, Section 14, and heating it

in a slow oven.

The open end should be kept up and the

compound heated sufficiently to allow it

to adhere to the laminations of the transformer.

After heating, the transformer should be allowed to cool for at

least 24 hours and then

returned to the S.P.U.

0) DISTORTION IN REPRODUCER UNIT

Distortion in the reproducer unit may be due to any of the following causes:

(a) Cone out of alignment.

Refer to Part II, Section 21.

(b) Leads from cone coil broken away from side of cone.

Make these leads fast with

a little shellac.

Any loose part in the cabinet will cause

A rattle.

Tighten all loose parts.

Figure 8-Method of adjusting trimming and compensating condensers

(9) LOW VOLUME AND WEAK SIGNALS

Low volume or weak signals may be caused by:

(a) Defective antenna system.

A poor antenna and ground or one in a shielded locality

may cause weak signals.

The suggestions given in Part I, Sections 1, 2 and 3, should

be followed if trouble of this kind is experienced.

(b) Defective Radiotrons.

A defective Radiotron in any stage may cause weak signals.

Before checking other causes it is a good plan to check all Radiotrons by inter-

changing them with ones of a similar type known to be in good operating condition.

If this condenser is badly out of

adjustment it will have the effect of making the receiver very insensitive.

To adjust

correctly refer to Part II, Section 13.

(d) Oscillator trimming condensers out of adjustment.

Should the oscillator trimming condensers be out of adjustment the receiver may be sensitive at certain portions of the tuning scale and very insensitive at other sections.

Should these condensers be

badly out of adjustment, only very loud local stations will be heard.

The correct

method for adjustment of these condensers is given in Part II, Section 12.

(e) Intermediate transformers not correctly tuned or matched.

Should the tuning con-

densers connected across the secondaries of the intermediate transformers be out of

adjustment, weak signals and poor tuning or, in some cases, no signals will result.

Refer to Part II, Section 14, for the correct method of adjusting the I.F.

trans-

formers.

Page 98

(f)

Defective A.F. transformer or output condenser and choke. A defect in any of these

parts will cause weak signals and abnormal operation.

Check by means of the con-

tinuity test and make any replacement that is necessary.

(g) Low voltage from S.P.U.

Check S.P.U. voltages at terminal strip with readings

given in Part II, Section 17.

Low voltages may be caused by a low emission recti-

fying tube or defective resistances in the S.P.U. or receiver.

Check by means of

continuity test.

(h) Open or short of various connections in receiver.

Check by means of continuity tests

and make any repair or replacement that is necessary.

Figure 9-180 K.C. Test Oscillator

[10) AUDIO HOWL

Audio howl may be caused by:

(a) Incorrect adjustment of R.F. compensating condenser.

A compensating condenser

adjusted to the verge of oscillation may cause a howl on nearby stations.

Adjust as

suggested in Part II, Section 13.

(b) Open A.F. condenser connections.

An open of the A.F. by-pass condenser may cause

a howl.

An open of the connections to the large

by-pass condensers may cause a howl.

(d) Defective volume control resistance.

Should there be an open or short in the volume

control or in its adjacent resistances an audio howl may develop.

Page 99

(e) Vibrating elements in receiver Radiotrons. A gradually developed howl may be due

to the loudspeaker causing the receiver Radiotron elements to vibrate. To over-

come this condition, interchange the Radiotrons in the receiver, especially the second

detector.

(f) Poor ground.

Install ground system as suggested in Part I, Section 3.

(g) Poorly soldered or corroded joints.

Any high resistance joint throughout the set

may cause a howl.

(h) Defective resistance

in S.P.U. or the receiver assembly.

An open resistance unit

may cause howl. Under such conditions it

is advisable to turn the set "off" until

the trouble is found, otherwise excessive voltage rise may cause further damage.

(i)

Neutralizing condensers in intermediate transformers out of adjustment. These con-

densers being out of adjustment might cause an I.F. stage to oscillate which will

result in a howl when a station is tuned in, especially at loud volume. Adjust the

neutralizing condensers as described in Part II, Section 14.

(j) Open of any of the several ground leads in the set. This may cause some of the

circuits to go into oscillation and result in a howl when a station is tuned "in".

Generally a loud hum will also be present.

The several grounding leads in the

Receiver Assembly and in the Socket Power Unit should be checked and any open or poorly soldered joint should be repaired.

[11) DISTORTED REPRODUCTION

Under normal conditions Graybar 340 will deliver a strong signal of excellent quality to

the loudspeaker.

The high sensitivity of the set makes it undesirable to operate the set at

full volume when receiving from nearby broadcasting stations.

If the loudspeaker production

is poor, test the output from the receiver.

A pair of phones may be used for this purpose.

Poor quality or distortion may be due to any of the following causes:

(a) Defective Radiotrons.

Though the receiver may be in operating condition a defective

Radiotron in any stage will cause distortion. This is especially true of, the second

detector, audio stage and the rectifier tube.

(b) High or low plate and grid voltages from the Socket Power Unit or a defective

resistor in the Receiver Assembly.

In the Socket Power Unit distortion may be

caused by a defective Radiotron UX-280 or resistance unit.

(c)

Defective A.F. transformer.

Check by means of

continuity

test

and replace

necessary.

(d) Trimming condensers out of adjustment.

Should the oscillator trimming condensers

be out of adjustment the beat signal may not be exactly the frequency to which the

intermediates

are tuned.

This

will cause weak signals and distortion of those

received.

This condition may or may not be present throughout the tuning range

of the receiver.

Adjust as described in Part II, Section 12.

(e) Receiver oscillating.

Should some circuit other than the oscillator be oscillating,

distortion will be experienced when tuning in a station.

This will be accompanied

by a whistle or squeal when the carrier wave of the station is tuned in.

To remedy

trouble of this kind see Part II, Section 10.

(f)

Intermediate transformers out of line or not properly matched.

This will have the

effect of giving distorted reproduction and reduce the sensitivity of the receiver to

a marked degree. Line up the entire I.F. transformer assembly as described in

Part II, Section 14.

[12) ADJUSTMENT OF OSCILLATOR TRIMMING

CONDENSERS

Two trimming condensors are provided for adjusting the oscillator circuit so that the

heat note will always be 180 K.C. throughout the tuning range of the receiver.

The most noticeable symptom of the oscillator trimming condensers being out of adjust-

ment is insensitivity of the receiver in some sections or throughout the tuning range.

check the adjustment of the trimming condensers as a possible cause of any noticeable insen-

sitivity in the receiver proceed in the following manner:

Page 100

(a) Procure the following equipment:

A modulated oscillator giving signals at 1,400 and 600 Kilocycles.

The test

oscillator shown in Figure 9 is

suitable for this purpose.

A long, thin, non-metallic screwdriver.

Such a screwdriver is shown in Figure

7 with its dimensions.

A 0-10 milliammeter.

Connect the milliammeter in series with the red lead

that turns to the receiver assembly as it enters the braided cable and connecting to

lug No. 2 of the S.P.U. terminal strip.

This places the meter in series with the plate

supply of the second detector.

(b) With the set in operation, place the oscillator in operation at 1,400 K.C. close to

the antenna lead and tune the set by adjusting the station selector until a deflection

caused by the external oscillator is obtained in the milliammeter.

Adjust volume

control so that deflection is not beyond scale of meter.

TRIMMING CONDENSE/RS

COMPENSATING COND.

A.F.

Vi° DEL

OSC.

I.F.

IST D E T

F -3!T 1.Fri

F-214°

r -Is.! 1.F,

TRANS.'

TRANS.

® ®Nr\

TUNING CON1?.

NEUTRALIZING COND.

ON\

CO4E4SER

R.F.

ANTENNA

COUPLING

STAGE

Figure 10-I.F. neutralizing and tuning condensers, oscillator

trimming condensers, and R.F. compensating condenser

340 (Figure 8) with the long, thin, non-metallic screwdriver until a maximum deflec-

tion is obtained in the milliammeter.

(d) Adjust oscillator for 600 K.C.

Tune in the set with station selector and then adjust

the trimming condenser to the left for maximum deflection of the milliammeter.

(el Now readjust at 1,400 K.C. as indicated in (b) and (c).

With

this

adjustment the

trimming condensers

are

correctly

adjusted

for

maximum efficiency, that

is, so adjusted

that the beat

signal will

be 180 K.C.

throughout the tuning range.

[13) ADJUSTMENT OF R. F. COMPENSATING CONDENSER

The radio frequency compensating condenser should not be touched unless it is definitely

ascertained that no other failure exists as a possible cause of receiver insensitivity, which is

the most noticeable indication of the need for adjusting the compensating condenser.

An oscillating condition of the receiver may be caused by improper adjustment of this

condenser.

A step by step procedure for making proper adjustment follows:

(a) Procure a long, thin, non-metallic screwdriver (see Figure 7). (b) Place receiver in operation in usual manner and tune in a weak station, preferably

at the middle or upper wavelengths.

If only a loud signal is available, disconnect

the antenna.

Graybar 600 Service Notes

Specifications and Main Features

Frequently Asked Questions

User Manual