General Radio Company 1110-A Service Manual

D

MAINTENANCE

OPERATING AND MAINTENANCE

l

NSTRUCTIONS

for

TYPE

INTERPOLATING

FREQUENCY

Form

July,

1110-A

ST'ANDARD'

678-C

1953

PRINTED

IN

U.S.A.

GENERAL RADIO COMPANY

CAMBRIDGE

NEW YORK CHICAGO LOS ANGELES

39

U.

s.

MASSACHUSETTS

A.

Panel View

and

of

the

the

Type

1110-A Interpolating Frequency Standard

Type

1110-PI Multivibrator

SPECIFIC

Frequency Range:

1110-A Interpolating Frequency Standard is from
to 1010 kc. The output frequencies of the 1110-PI
Multivibrator Unit are 1.0- and 0.1-Mc fundamentals

with harmonics up to 200 or more.

Calibration

1000 divisions corresponding to 0.001 per cent or 10
parts per million per division.

A list of check settings is provided on the panel. This
check can be made at any time by simply plugging a
set of headphones into the jack or binding posts provided
on the panel. A trimmer control on the panel provides
for adjusting the oscillator to agreement with the crystal.

To facilitate conversion of the dial readings from
their basic percentage or parts per million values of
frequency increment to fractions of a megacycle or of

0.1 Mc (100 kc), a table listing the number of dial divi­sions for frequency increments of 1.0 Mc and 0.1 Mc at
each harmonic from 100 to 220 is given on the panel. A
simple slide-rule ratio then gives the desired frequency
increment.

Crystal Oscillator:

within

1

temperature. It should be reliable to within
per million at ordinary room temperatures. The crystal
frequency can be checked and adjhstedin terms of stand­ard frequency transmissions from

part in a million of correct frequency at room

The output frequency range of the

:

The variable frequency oscillator dial has

The crystal oscillator is adjusted to

f

10 parts

WWV

using an

1000

external receiver, maintaining the variable oscillator at
exactly 50 kc in terms of the crystal.

Accuracy of Measurement:

measurement is
lator dial directly.
in terms of the crystal, the over-all accuracy is limited
principally by the error of the crystal.

Vacuum Tubes:

2

-

6AC7
4 - 6SN7-GT 1 - 5R4GY
1 - 6557

1 - 6SA7 1 - 2LAP-430 (Bridge Circuit Lamp)

Power Supply:

cycles.

Power Input:

Mounting:

(attached to 1110-A hy cable) small metal cabinet.

Accessories Supplied:

1110-PI Multivihrator Unit with connecting cable.

Accessories Required
Dimensions:

behind panel, (length)

inches. 1110-P1 (length)
inches.

Net Weights:

TYPE 1110-P1 Multivihrator Unit,

+Z5 parts per million using the oscil-

If

the oscillator is carefully trimmed

The following tubes are supplied:

3

-

6J5GT /G

1

-

9001

Either 105-125 or 210-250 volts, 50-60

85 watts from 115-volt, 60-cycle line.

TYPE 1110-A Relay Rack; TYPE 1110-P1

:

1110-A Panel (length) 19 x (height) 8%;

Type 1110-A assembly, 40 pounds;

The over-all accuracy of

Line connector cord, and TYPE

Head t,elephones.

17% x (height) 8% x (depth) 14

9%

x (height)

5%

x (depth)

735 pounds.

5%

Manufactured and sold under United States Letters Patent:

United States Letters

Patent owned or controlled by American Telephone and Telegraph

Company, and under all patents and patent applications of Dr.

piezo-electric crystals and their associated circuits.

G.

W.

Pierce pertaining to

OPERATING INSTRUCTIONS

for

Type

The Type 1110-A Interpolating Frequency Standard

is

designed as a means to improve greatly the accuracy
of frequency measurements made with the heterodyne­frequency meters, such as the Types 720-A and 620-A.

The Type 1110 -A Interpolating Frequency Standard

comprises a standard frequency source having a range of

1

per cent, from 1000 to 1010 kc, and

Type

1110-PI, a harmonic generator of the multivibrator

type which generates multiples of
adjustment of the frequency
coverage

1

Mc harmonics and above lOMc, using 100 kc harmonics.

Standard

1010 kc, and isthe sum of a crystal oscillator frequency
of

950

50 to 60 kc. The oscillator
1000 divisions.

is

obtained at frequencies above 100 Mc, usirg

The output of the Type 1110-A Interpolating

is

a

single frequency, lying between 1000 and

kc and of a bridge-type tuned-circuit oscillator of

1110-A

1Mc and 100kc. By

of the standard, complete

is

controlled by a

Interpolating Frequency Standard

is

used with the

PRINCIPLES OF OPERATION

dial

having

SECTION 1.0

INTRODUCTION

SECTION 2.0

Thus integral standard frequencies can be generated for
calibration
can he generated to match any desired frequency,

the approximate range of measurement
200 Mc. With the Type 720-A Heterodyne Frequency
Meter, the range
setting for zero beat
damental or harmonic,
on the heterodyne frequency meter. The
Interbolating Frequency Standard provides a means of
evaluating more precisely the frequency to which the dial

is

set.

trol the

Unit. The multivibrator fundamental frequencies are 1.0
MC and 100 kc. A large number of harmonics are avail­able but in
utilized

quency Meters,

purpses, or an accurately known frequency

With the Type 620-A Heterodyne Frequency Meter,

is

from 10 Mc to

is

from 100 Mc to 2000 Mc. The dial

with

the unknown signal, either fun-

is

obtained in the usual manner

Typ 1110-A

of

The output frequency

multivibrators of the

particular the range from the 100th to 200th

with

the Typs 720-A and 620-A Heterodyne Fre-

the standard

Type

1110-P1 Multivibrator

is

used to con-

is

CRYSTAL

OSCILLATOR

950

kc

fc

-

-

d

L- C

OSCILLATOR

50-60

8

SUPPLY

kc

-

fo

m

------------------

MODULATOR

MAIN

ASSEMBLY

Figure

*

FILTER

/fc + fo

fc

Jc - fo

1.

Block Diagram

and Type 1110-P1

I

I

I

I

I

fc + fo

1

I

)

!

+

MULTNBRAm

/

1Mc

I

I I

I

I

.*

I

I

I

I

I

I

'

_1

for

Type 1110-A

I

I

MULTNIBRATOR

1

100

I

1110-PI

I

MULTIVIBRATOR

I------J

UNIT

kc

I

I

1

I

I
I

I

<I

-1

I

I

Mc

100

yc

720A

HET

0.1

10

M

c

620A

HET. FREQ. METER

I

HARMONICS

200

IIIII

FREQ.

METER

HARMONICS

IIIIII

lqc

20

Mc

GENERAL RADIO COMPANY

Figure
Interpolation

66

sliding harmonics." This process

1

is

a block diagram of the system.

is

accomplished by the method of

is

illustrated in Fi-

gure 2. When the dial of the interpolating frequency

standard

fs,

When n

is

that
the range

dial

difference,

UlAL

isset

at

zero, harmonics d the output frequency,

are spaced at frequency intervals fs in the spectrum.

is

100, the available

1%

range of variation of fs

just sufficient to cover the range from nfs to (n+l)fs,

is,

Af

is

equal to f

is

therefore 2fs. To measure a frequency, the

is

advanced to move nfs to

A,

from which

ADVANCED;

Af

f,

I

=

=

A

IN

DIAL DIVISIONS

DIVISIONS

nf, + Af

s.

At the 200th harmonic (n=230),

riffs,

giving a scalc

A£

can be calculated.

I

PER

MEGACYCLE

I

I

100

<n

I

5

I

<

200

Figure 2.

As the oscillator control

scale, the outplt frequency of the standard

1000 to 1010 kc, a range

harmonics of the

multivibrators controlled by these out-

put frequencies are similarly changed by

100th harmonic, the increase

times the original

is

moved through the range from 100' to

1

Mc multivibrator, or from 10.0 to 10.1 Mc for the 100

fundam

of

1%.

mtal;

is

moved from zero to

is

varied from

The frequencies of the

1%.

of

1%

gives a frequency 101

that

is,

the 100th harmonic

101

Mc for the

full

At the

kc multivibrator. For
variation

is

greater than the fundamental frequency so
that complete coverage
above that of the

While complete coverage

quencies below that

is

coverage
each harmonic
coverage
the coverage
Mc. And

often very useful. The range covered at

is

is

readily estimated. For example, at 95 Mc

is

again,

at 67 Mc the coverage

all

higher harmonics the range of

is

obtained at

all

100th harmonic.

is

not obtained at fre-

d

the 100th harmonic, the substantial

I%, so

0.95 Mc, that

that

the extent of the available

is,

from 95,00 Mc to 95.95

is

0.67 Mc., that is,

frequencies

from 67.00 Mc to 67.67 Mc.

11

When the oscillator control of the Type
Interpolating Frequency Standard
precisely, when the oscillator

is

is

set at

set at zero, or more

50

kc, (which can

10-A

be checked in terms of the internal crystal frequency)
the

output frequency

is

just 1000 kc,

and

all

multivibrator
harmonics are then integral standard frequencies which
can be conveniently used in calibrating, or in

checking

the calibration of, the heterodyne frequency meters.

Such calibrations are needed to identify the multivibrator

harmonic used in a measurement. The accuracy of the
frequency meter calibration does not otherwise enter
into the final result.

The basic method

1.

Set the heterodyne frequency meter to zero beat

with the frequency being measured.

sult

is

then given by the dial reading of the heterodyne

of

measurement

is

then as follows:

An

approximate .re-

frequency meter.

2.

Couple the output of the multivibrator to the fre­quency meter. Advance the control of the interpolating
standard from zero until the

first

strong beat between
a multivibrator harmonic and the frequency meter is ob­tained. Set to zero beat.

3.

The frequency being measured

is

then given

by

the

frequency of the multivibrator harmonic being used

(identified automatically by the frequency meter

plus

an increment in frequency (determined from the

readmg),

dial

of the interpolating frequency standard).

Detailed

examples are given under Operation, Section

4,

.

SECTION 3.0

INSTALLATION

1.

Plug the power cord into the instrument (rear) and

connect to power line of voltage and frequency

as

marked

3.

put terminal of the multivibrator unit to the frequency

on nameplate beside the socket. meter.

2. Plug the cable of the Type 1110-P1 Multivibrator

Unit into the multipoint socket on the panel of the

11

10 -A Interpolating Frequency Standard.

Type

4. A pir

into the heterodyne frequency meter, or the jack on the

panel of the interpolating frequency standard, should be
provided.

Provide a short coupling wire from the desired out

of telephone receivers, which can be plugged

-

TYPE

1110-A

INTERPOLATING FREQUENCY STANDARD

SECTION
OPERATION

4.1

Use of Instrument

4.11

Throw on power switch

frequency

of the multivibrator unit, according to whether a

0.1

mended that both multivibrators be used continuously.

zero. Adjust compensator control for zero beat with
phones plugged into jack on interpolating frequency
standard.

meter output.
vary its frequency.
at every

0.1

(or
cy meter to zero beat with the frequency to be
Note reading d frequency meter. Couple the output of the
multivibrator unit to the frequency meter and listen in
telephones plugged into the heterodyne frequency meter
output. Advance the dial of the interpolating frequency
standard from zero until the first strong beat
within the dial range corresponding to the harmonic used

(see
interval from zero to

standard dial for zero beat. Note the final dial reading.
(For example,
sults,
the final dial reading

meter determine which multivibrator harmonic was used.

(Example: Reading

162.

the number

162

frequency standard divided by the number of divisions
from the table gives the fraction
which must
to obtain the

163

divisions. The final result

standard, Throw on one

Mc harmonics output

4.12

Set

dial

of interpolating frequency standard to

4.13

Plug telephones into heterodyne frequency

Turn on heterodyne frequency meter and

1

Mc in the range

Mc in the range

4.14

In

making

known harmonic) frequency of the heterodyne frequen-

4.16).

In this example, the first strong beat in the

4.15

Carefully set the interpolating frequency'

199.8

the oscillator calibration should be checked before

4.16

From the reading of the heterodyne frequency

Enter the table on the panel at

of

divisions required to cover 1 Mc between

and

163

MC.)

The final

be

added

final

result. Example: Table value at

Mc

is

617.3

divisions. Final

is

desired. It

Zero beat points should be obtained

100

10

to

20

measurements,

617.3

divisions

divisions). For the most precise re-

is

taken. See Section

is

162.3

Mc. The harmonic used

dial

tothe frequency of the used harmonic

is

of

the interpolating

of

the power switches

1

Mc or

is

not recom-

to

200

Mc or at every

Mc.

set

the fundamental

measured.

is

obtained

is

used.

4.2

following.

is

162-163

reading ofthe interpolating

of

a megacycle

Mc and find

br

O.lMd

162-

dial

reading was

1988

4.0

initial frequency
The changes in frequency can then
in dial reading from the reading for the initial condition.
Since each division very closely represents a change of

10

parts per million (see Section
dial reading are easily converted to frequency changes in
parts per million. Also, since each dial division repre­sents a change in the control frequency
changes in dial
at the test oscillator frequency by multiplying by

by the number

of the initial frequency.

4.18

oscillator whose frequency

multiple of

readings corresponds almost exactly with the parts per

million change in the oscillator frequency. However,
the oscillator frequency lies just below the next higher
multiple of

1

part per million

that
would be measured by raising the

162

Mc to
corresponds to
cycles. One prt per million would be
stead of

purposes.

162.98

4.2

Checking the Interpolation Oscillator

4.21

pnel of the Type

ard, the calibration of the

checked in terms
check points, over the entire range of the oscillator dial,
are listed in the table on the

4.22

any small errors in calibration can be made zero at any
of the check settings by use

this,

To do
the tableand adjust the compensator knobto get zero beat.

4.23

ment

is

desired, the oscillator should be checked, and
corrected,
obtained between the standard and the frequency meter,

Paragraph

is

measured as previously described.

be

read as the changes

4.18),

the changes in

of

10

cycles, the

readirg are convertible into cycles change

10

and

of

the harmonic used in the measurement

When observing changes in frequency of an

is

only slightly higher

1

Mc, the parts per million change by dial

1

Mc for example

is

162.98

Mc. On the dial, each division then

10

parts per million

162.98

162.98

Mc, it

cycles. This frequency

162

harmonic from

of

162

Mc or

162.00

cycles, which error is negligible for many

By

plugging the telephones into the jack on the

1110-A

of

Assuming the oscillator alignment

set the

When the best possible accuracy of measure-

4.14

dial

if

necessary, immediately after the beat

above. The final reading

Interpolating Frequency Stand-

50-60

kc oscillator can be

the crystal oscillator. A number of

of

the compensator control.

to the number

of

divisions givenin

is

than

is

evident

1620.0

cycles, in-

is

normal,

is

then taken.

if

a

fx

=

162,324

In other words, the frequency of the

increased

in frequency of an oscillator resulting from arbitrary
changes in the conditions of operation. In this case, the

0.324

4.17

Many times it

Mc in going from

is

Mc

16hd

harmonic was

162

Mc to fx.

desired to measure changes

4,3

Checkiw the Crvstal Oscillator

4.31

Since the multivibrator unit provides output
frequencies at all of the frequencies used for the Bureau
of Sandards' Sandard Frequency Transmissions, it
possible to check the crystal oscillator by obtaining abeat
between the standard frequency and multivibrator har-

If

monic in a short-wave receiver.
made to oscillate or
tor, the check can

if

it includes a heterodyning oscilla-

be

made very precisely.

the receiver can be

is

GENERAL RADIO COMPANY

4.32 After picking up the standard frequency trans­mission, couple the appropriate multivibrator output into
the receiver. The dial of the interpolating frequency

standard may be advanced slightly from zero so as to
produce an audible beat in the receiver. This will facili­tate

making

the coupling adjustments.

is

curve, the change in shape

be

can thus

made to fit the ideal curve at any mint where

a means for comparison

negligible. The dial reading

is

available.

In

this instrument

the crystal oscillator furnishes this means at a suffi-

of

ciently large number

points covering the entire range

of the oscillator.

4.33 Plug the telephones into the panel jack on the

interpolating frequency standard and carefully set the

"0"

oscillator to obtain zero beat at the check pint

dial.

It

the

does not matter

actly zero as long as the zero beat

if

the

dial

reading

is

maintained. Check

is

on

not ex-

in the short wave receiver to determine the difference in
frequency between the standard frequency and the output

of the interpolating frequency standard. This difference
should be only a few parts in a million.

4.34 To correct the crystal frequency, remove the

carer in the lower left

snap

of

the interpolating frequency
standard panel and use a screw driver to adjust C-17.
NOTE: At each adjustment of C-17, carefully reset the
oscillator dial to zero beat

against the crystal at the

"0"

reference point. Then check the output frequency of the
standard against the standard frequency transmission.

is

The normal crystal frequency

is

lator

set to zero beat against the crystal at the

reference point, its frequency

950 kc. When the oscil-

"0"

is

close to 50 kc and

is

actually 1/19th of the crystal frequency. The control

is

frequency for the multivibrator unit
and

is

close to 1000 kc.

The output frequency matched
against the standard frequency transmission
quency multiplied by the number

if

(For example,

is

sion

used, the outputafrequencp must be five times the

the 5 Mc standard frequency transmis-

the sum of these,

is

this fre-

of

the harmonic used.

control frequency.)

4.4 Checking the Oscillator Alignment

4.41 To obtain a direct-reading linear calibration

of the oscillator several conditions must be met simul­taneously.
be correct.

First, the plate shape of the condensermust

Second, the initial circuit capacitance must

have the correct value, appropriate to the change in ca-

pacitance produced by the shaped rotor plates. When
these conditions are met, the calibration will be linear
and the correct frequency ratio (maximum frequency

ded by minimum frequency)

the correct ratio

is

have the oscillator cover the range from

will

be obtained.

60/50 = 1.20, since it

50

In

is

to 60 kc,

tween the zero and 1000 division points on the dial.

divi-

this case,

desired to

be-

In

order to have the oscillator cover exactly the specified

is

range it

so that the initial frequency

then necessary to adjust the circuit inductance

is

exactly 50 kc. Manufactur-

ing tolerances impose a limit on just how closely this

In

ideal can be approached.
to within 5 two divisions

4.42

Small

corrections can be made by means of the

this instrument, alignment

is

considered satisfactory.

compensator condenser (part of C-7) panel control. For

corrections, the primary effect

tial capcitance

is

to move the calibration curve bodily up

or down, and the secondary effect

changing the

is

to changethe shape

ini-

of

of the calibration curve. Over small portions of the

4.43 The list

of

oscillator check points on the panel
plate includes the principal points. Many other points can
be found

these can be identified

and

used to advantage

and

in many instances. The oscillator frequency at any zero

is

given

by

beat point
integers. The principal pints are given when

has

such value

n

60 kc.
cillator beats

tal. The

subtracting

In

this

case, the 16th to 19th harmonic of the os-

with

dial

reading of the ideal oscillator

50 kc from

(in kc) by 100. For example, a check point

fo = T950 kc, where m and n are

as

to give

fo

values lying between 50 atd

the fundamental frequency

fo

and multiplying the remainder

m

=

of

the crys-

is

given by

is

foundat

1

and

52.055 kc, (where n = 73, m = 4). Subtracting 50 kc,

2.055 kc gives a

reading

of

205.5 divisions (as listed

dial

in the table).

If

4.44

the oscillator requires realignment, it

is

evident from the foregoing that the misalignment might

of

be due to a change

capacitance, or of inductance or a
combination of both. The first test, then, should be to
check the
cillator frequency at equal steps in
serving
latter
standard

1

kc (or 500 cycles) from 50 to 60 kc and
noted.
constant, the capacitance adjustment

differences are not constant readjustment
capacitance must be made.
toward the

"uphill"
to correct it.
ings

capacitance.

dial

readings for equal steps in frequency. The

is

generally more convenient where a frequency

is

available. The oscillator

If

the differences

high

frequency end

and

an increase

(Part

d

the top

dial.)

This

is

done

by

measuring the

dial

reading, or ob-

is

checked at every

dial

of

successive

If

the differences increase

of

the

of

initial capacitance

of

C-7, accessible through the open-

dial

readings are

is

correct.

of

dial,

the curve slopes

is

the initial

os-

readings

If

these

required

4.45 When the capacitance has been checked, the
next step
removing the shield can from

is

to adjust the inductance. This

L-2

(to right

is

done by

of

C-7 con-

denser assembly) and loosening the set screw holding

the upper coil just sufficiently to permit the

coil to be
moved. Replace the shield can. Set the condenser dial
at zero and check the oscillator frequency against a

by

frequency standard. Adjust L-2

carefully moving the

the upper coil (upward to raise the frequency). When

is

the frequency

exactly 50 kc, lock the upper coil in

position.

4.46

If

the calibration of the oscillator

is

not badly

in error, the frequency can be checked against the inter-

is

nal crystal, but there
frequency if the error
setting to the

50 kc point, zero on the dial, a quick check

danger of setting to the wrong

is

appreciable. However, if, after

of the principal check points at 277.8, 588.3 and 937.5

is

divisions

made, any error will immediately be dis-

closed because these additional points will not then agree

all

settings listed in the table.

at

TYPE 1110 -A INTERPOLATING FREQUENCY

STANDARD

4.5 Checking Control of Multivibrators

4.51 For

oscillating receiver set to obtain a beat against a low
harmonic of the multivibrator, at 2,
causse of the direct signal from the control oscillator,

is

not recommended that a setting of 1 Mc be used. No
attemI;t to adjust multivibrators should be made
have been in operation at least 15 minutes.

4.52
quency of the harmonic will vary erratically and the beat
tone heard in the receiver will be very unsteady. The

multivibrator adjustments are accessible from the top of
the Type 1110-P1 Unit, on removing the dust cover.
Check that R-108, in the Type 1110-P1 Multivibrator,

is in the
an insulated screw driver or alignment tool) to either
side of its previous setting, checking with the receiver
to obtain a clear and steady beat tone. When such a point
has been obtained, leaving the receiver adjusted, note the
range over which C-108 can be turned while obtaining a
steady beat tone in the receiver. Make the final setting
of C-108 at the center of this range.

an oscillating receiver set to obtain a beat against a low

harmonic

of the direct signal from the control oscillator,

recommended that a setting of

to adjust multivibrators should be made until they have

been in operation at least 15 minutes.

quency of the harmonic will vary erratically and the beat
tone heard in the receiver will be very unsteady. The
multivibrator adjustments are accessible from the top
of the Type 1110-P1 Unit, on removing
Check that R-101, in the Type
in full clockwise position. Then adjust C-101 (using an
insulated screwdriver or alignment tool) to either side
of
obtain a clear and steady beat tone. When such a point
has been obtained, leaving the receiver adjusted, note the
range over which C-101 can be turned while obtaining a
steady beat tone in the receiver. Make the final setting
of C-101 at the center of

metal tip, the

full

4.53 For checking the 100 kc Multivibrator, use

4.54

its

previous setting, chetking with the receiver to

4.55 Unless the screwdriver has only a very small

checking the 1 Mc Multivibrator, use an

3,

4, or 5 Mc.

until

*If

the multivibrator

cloclwise position. Then adjust C-108 (wing

of

the multivibrator, at 200 to 900 kc. Because

is

not in control, the fre-

it

1

Mc be used.

Tf

the multivibrator

capcity added when the screwdriver

is

not in control, the fre-

1110-P1 Multivibrator

this

range.

No attempt

'che dust cover,

is

Be-

they

not

is

it

is

in

the slot of the condenser will shift the
frequency slightly. The range of adjustment of the con­denser must then be determined by lifting the screw­driver out of the slot after each adjustment.

4.6

Chkcking Calibration of Frequency Meter

4.61 As'described, the use of the
quency standard depends on the calibration of the fre­quency meter for the identification of the harmonic used.

If

the calibration were in error, the final result would be
in error in that an incorrect harmonic number would be
used,

4.62 The calibration
quency meter may be calibrated, as follows: Set the dial
of the interpolating frequency standard at zero. Set the

frequency meter at the reading believed to be 101 Mc,

and carefully adjust to zero beat. Leaving the frequency
meter alone, move the dial of the interpolating frequency
standard to

tained. If it

101 Mc, and from this key the other calibration points
are identified.
divisions, then the frequency was set at 102 or 100 Mc
respectively.

process is the same as before, using the 0.1 Mc output of
the interpolating frequency standard. Set the dial of the
interpolating frequency standard to zero. Set the fre­quency meter to the reading believed to
carefully adjust to zero beat. Leaving the frequency
meter alone, move the dial
standard to

obtained.

10.1 Mc, and from this key the other calibration points
are identified.
divisions, then the frequency meter was set at 10.2 or

10.0 Mc respectively.

identifying the key pint
lating frequency standard for zero beat at the
tal check
ly 1.0 or 0.1 Mc.
range and
be made.

1000 divisions. Zero beat should again be ob-

is,

the frequency meter has been set to

If

zero beat

If

4.63

4,64

the frequency meter covers 10 to 20 Mc, the

1000 divisions. Zero beat should again be

If

it is, the frequency meter has been set to

If

zero beat

In

either case, a calibration can be made after

wint. The outpt frequencies are then accurate-

l3y

marking each point, a complete calibration can

is

readily checked, or a fre-

is

reached at 990 or 1010

of

the interpolating frequency

is

reached at 990 or 1010

by

setting the dial of the interp-

tuning the frequency meter over its

mnltivibrator

interwlating fre-

be

10.1 Mc and

"0"

crys-

GENERAL RADIO COMPANY

Type

Service and Maintenance Instructions

1.0 FOREWORD

1.1

This Service Information together with the in­formation given in the Operating Instructions should
enable the user to locate and correct ordinary difficul­ties resulting from normal usage.

1.2 Most of the components mentioned in these in-

be

structions can

1.3 Major service problems should be referred to

the Service Department which will cooperate as far as

possible by furnishing information and instructions, as
well as by shipping any replacements
be required.
old, a reasonable charge may be expected for replace­ment

parts

is

returned.

located by referring to the photographs.

parts

If

the instrument

or for complete reconditioning

is

more than bne year

if

which may

the standard

1110-A

3.3 NO OUTPUT SIGNAL AT SOCKET SO-1; refer

to Section 6.0.

J-1;

3.4 NO OUTPUT SIGNAL AT TEL JACK,

to Section 7.0.

3.5 NO OUTPUT

refer to Section 8.0.

3.6 NO OUTPUT FROM THE VARIABLE OSCILLA-

TOR; refer to Section 9.0.

3.7 OUTPUT SIGNAL IS ROUGH OR UNSTEADY;

refer to Section 10.0.

3.8

OUTPUT BEATS INDISTINGUISHABLE FROM

THOSE PLUS OR MINUS 50 KC AWAY; refer to Sec-

tion 11.0.

FROM THE

CRYWAL

OSCILLATOR;

refer

1.4 Detailed facts giving type and serial numbers of
parts,

as

the instrument and

should always be included in your report to the Service

Department.

2.0 GENERAL

If

the standard becomes inoperative, a few simple
checks should be made before any circuit checks are
made.

2.1 Make certain the voltage and frequency of the

power line source are correct.

2.2 Test the power supply cord for open circuits or

for poor contacts in the power outlets.

2.3 Check fuses

of the instrument, for open circuits and be sure they are

tight in their holders.

2.4 Be sure that all tubes are completely seated in

their sockets.

3.0 INSTRUMENT INOPERATIVE

3.1 NO OUTPUT SIGNAL AT THE

JACK; refer to Section 4.0.

F-1 and F-2, mounted at the rear

well as operating conditions,

1

MC OUTPUT

3.9 MAIN DIAL IS OFF CALIBRATION; refer to

Section 12.0.

3.10 POWER SUPPLY INOPERATNE; refer to Sec-

tion 13.0.

3.11 VACUUM-TUBE DATA; refer to Section 14.0.

4.0 NO OUTPUT SIGNAL AT THE
This condition can be readily detected by a lack

beat notes in the heterodyne-frequency meter when at­tempting to identify

4.1 Check switch S-102 for proper operation.

4.2 Make sure that rheostat R-108

clockwise position.

4.3 Check tube V-103 and operating voltages; refer

to Section 14.0.

4.4 Check resistors R-108 through R-112 for open

and short circuits and proper values.

4.5 Check capacitors C-108 through C-112 for open

and short circuits. Capacitors C-108 and C-110 should

have any accumulated dust blown out of their plates.

an

unknown frequency.

1

MC OUTPUT JACK

is

at

its

maximum

of

3.2 NO OUTPUT SIGNAL AT THE 100 KC OUTPUT

JACK; refer to Section 5.0. circuit.

4.6 Check inductor

L-101 for an open or a short

TYPE 1110-A INTERPOLATING FREQUENCY STANDARD

4.7 Check tube V-104 and operating voltages; refer

to Section 14.0.

4,8 Check resistors R-113, R-114 and R-115 for

6.6 Check capacitors C-25 through C-29 for open

and short circuits.

6.7 Check inductor L-6 for an open or a short circuit.

open and short circuits and proper values.

6.8 Check the elements of the filter sections LC-1,

4.9 Check capacitors C-113, C-114 and C-115 for

LC-2, LC-3 and LC-4 for open and short circuits,

open and short circuits,

4.10 Check L-102 for an open or

a

short circuit.

7.0 NO OUTPUT SIGNAL AT TEL JACK,

3-1

This condition can be detected by plugging a pair

5.0 NO

OUI'PVT SIGNAL AT TEE 100 KC OUTPUT JACK

of headphones into the TEL jack and listening for the
beats listed on the left hand plate on the panel.

5.1 Check switch S-101 for proper operation.
The voltage from the high potential terminal of

5.2 Make sure that rheostat

mum clockwise position.

R-101

is

set to its maxi-

TEL jack,

with the main dial set to 0. (Tone will be heard for all

J-1, to ground should be about 5.0 volts +20%

positions of the COMPENSATOR control.)

5.3 Check tube V-101 and operating voltages; refer

to Section 14.0.

7.1 Check that jack

3-1

is

making proper contacts.

5.4 Check resistors R-101 through R-105 for open 7.2 Check tube V-3 and operating voltages; refer to

and short circuits and proper values.

5.5 Check

and short circuits,

capcitors C-101 through C-105 for open

Cawcitors C-101 and C-103 should

have any accumulated dust blown out of their plates.

Section 14.0.

7.3 Check resistors R-15, R-16 and R-17 for open

and short circuits and proper values.

5.6 Check tube V-102 and operating voltages; refer 7.4 Check capacitors C-12 through C-16 for open

to Section

14,0,

and short circuits. Turn the main

dial

to settings both

above and below 10 divisions which is necessary in the

has

5.7 Check resistors R-106 and R-107 for open and event that the variable oscillator

gotten out of align-

short circuits. ment.

5,8 Check capacitor C-106 for an open circuit.

6.0 NO OUTPUT SIGNAL AT SOCKET

SO-1

This condition can be detected by the following

procedure. Disconnect the

Type

1110-P1 Multivibrator

from the Type 1110-A Standard by pulling out plug

PL-101. Connect a 1000-ohm resistor between ter-

minals

#7 or #8 and #12 of socket SO-1. Measure the

voltage across this resistor using a vacuum-tube volt-

meter. This should be 6

-

11

volts ax.

A low voltage
or no voltage will cause the multivibrators to fall out
of control.

6.1 Check tubes V-6, V-7 and V-8 and operating

voltages; refer to Section 14.0.

6.2 Check resistors R-24 and R-30 for open and

short circuits and proper values.

6.3 Check capacitors C-37 through C-44 for open
and short circuits and leakage. Capacitors C -40 and
C-42 should have any

accbmulated dust blown out of

their plates.

6.4 Check tube V-5 and operating voltages; refer
to Section 14.0.

6.5 Check resistors

open and short

circuits and proper values.

R-14A, R-20 through R-23 for

7.5 Check inductor L-4 for

an

open or a short circuit.

7.6 'Refer to Sections 8.0 and 9.0.

8.0 NO OUTPUT FROM THE CRYSTAL OSCILLATOR
The output measured from the arm of rheostat

R-14A to ground should be 0.9 - 1.5 volts ax. as mea­sured with a vacuum-tube voltmeter.

8.1 Check tube V-4 and operating voltages; refer to

Section 14.0.

8.2 Check resistors R-13, R-18 and R-19

for open

and short circuits and proper values.

'

Check capacitors C-17 through C-24 for open

8.3

and short circuits.

8,4 Check inductor L-5 for an open or a short circuit.
8,5 The

oscillating.

Quartz

Plate, Type 376-L, may have stopped

If

so a very light tap on its case should

start it again,

In

8.6

case this crystal

is

defective it should be re­ported to the Service Department immediately. Under
no circumstances should the holder be opened or the
seals broken

the user unless authorized

by

the Service

by

Department as this procedure will void the guarantee,

GENERAL RADIO COMPANY

The General Radio Company will not be responsible for
the proper operation of the standard

if

the crystal seals

have been broken.

9.0 NO OUTPUT FROM THE VARIABLE OSCILLATOR
The output of this oscillator, measured from pin

#8

of tube V-5 to ground, should be approximately 1.4

volts

a.c. measured with a vacuum-tube voltmeter, (The

main dial should be set at 500

divisions,)

9.1 Check tubes V-1, V-2 and V-10 and operating

voltages; refer to Section 14.0.

9,2 Check resistors R-1 through R-12 and R-14 for

open and short circuits and proper values.

9.3 Check

capcitors C-lthrough C-5 and C-7 through

C12 for open and short circuits.

9.4 Check inductors

L-1, L-2 and L-3 for open and

short circuits.

9.5 Set dial at 500, adjust rheostat

R-7A so that the

voltage measured across R-10 (or pin #4, V-2 to ground)

is

3.0 volts.

10.0 OUTPUT SIGNAL IS ROUGH OR UNSTEADY

12.0 MAIN DIAL IS OFF CALIBRATION
The dial readings should be within

the settings shown on the

is

checked in terms of the crystal oscillator fre-

tor

pel when

52 divisions of

the

variable oscilla-

quency. The COMPENSATOR control should be set for
zero beat with the main dial set to

0.

12.1 The frequency of the crystal oscillator should

be checked against a frequency standard or

by

the method
outlined in Paragraph 4.3 of the Operating Instructions
by comparing it with the standard frequency transmis­sions of the National Bureau of Standards, radio station

WWV.

The crystal frequency can be adjusted

The crystal oscillator frequency

is

950 kilocycles.

by

resetting capa-

citor C-17, available from the front panel.

12.2 Check the frequency alignment of the variable
oscillator as outlined in Paragraphs
Operating Instructions.

If

realignment

4,42 and 4.43

is

of

the

necessary,
follow the procedure of Paragraphs 4.44, 4.45, 4.46 of
the Operating Instructions.

12.3

If

the above procedure does not serve to adjust
the frequency and span of the variable oscillator cor­rectly, then the main capacitor
this

is

the case, it will be necessary to return the com-

is

probably at fault.

If

plete instrument to the factory for repair.

Type

Themultivibratorsin the

1110-P1 are proba­bly out of control. Check that a control voltage for the
multivibrators

is

available by following the procedure
of Section 6.0. The multivibrators can be checked and
set by following the procedure of Paragraph 4.5 of the
Operating Instructions.

10.1 Refer to Sections 4.0 and 5.0.

11.0 OUTPUT BEATS INDISTINGUISHABLE FROM

THOSE PLUS OR MINUS 50 KC AWAY

This

is

an abnormal situation but little can be
done to correct it. Normally if such spurious beat
notes are present, they are the result of a modulation

of the multivibrator control voltage. The multivibrator
harmonics are modulated and each

appars as a

carrier

frequency with upper and lower side bands, where the

deslred harmonic frequency

is

the carrier.

If

each beat
has the same amplitude or intensity the correct one can
always
instrument the middle beat

be

identified

as

the center beat note.

is

always the stronger.

In

a

normal

13.0

POWER SUPPLY 15TOPERATIVE

13.1 Check tube V-9 and operating voltages; refer

to Section 14.0.

13.2 Check condition of fuses

F-1 and F-2.

13.3 Check capacitors C-45 and C-46 for short

circuits.

13.4 Check operation of switch

S-1.

13.5 Check that tranSformer T-1 has continuity of

windings.

13.6 Check resistors R-26 through R-29 for open

and short circuits and proper values.

13.7 Check capacitors C-47 through C-50 for open

and short circuits.

TYPE 1110-A INTERPOLATING FREQUENCY

14.0 VACUUM TUBE DATA

STANDARD

pin

Tahle

to

ground,

d

tube

unless

socket

voltages

measured

othe~.wise indicated,

from

using

socket

a

20,000

TYPE 1110-A

ohms-per-volt voltmeter

vary

voltages may

+20%.

(Weston

772

Analyzer).

D-C

TYPE

1110-PI

--

CONDITIONS:

1110-P1

Type

Input:

1

Mc multivibrator turned ON.

Main dial set to

connected to Type

115

v.

a.c.,

60

cycles, power ON.

0.

1110-A.

PARTS LIST

RESISTORS CAPACITORS

.

BW-1/2
BT-1

BT-1

BT-1/2

BT-1/2

BT-1
X-1/2
W
X-1/2
BT-1

BT-1/2

BT-1

BT-1

BT-1

BT-1
W

BT-1

B$-1

BT-1

BT-1

BT-1

BT-1

BT-1

BT-1

BT-1

BW -1/2

BT-1

BW -2

BW -2

BW-2

BT-2

-21BF*

REC

IRC
IRC
IRC
IRC
IRC
IRC

(C.C.Co.)

IRC

(C.C.Co.)

IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC
IRC

IRC
IRC

REC -20BF
REC-20BF

GR
IRC
IRC
IRC

IRC
IRC
IRC

GR

IRC
IRC
IRC

IRC

IRC

301-465
BT-1/2
BT -2
BT-1/2
BT-2
BT -1/2
BT-1/2

301-465
BT-1/2

BT-1/2

BT-1/2

BT-1/2

BT-1/2

MISCELLANEOUS

S-1

=

Switch

=

S-101

Switch

S-102 = Switch
Q-1

=

Quartz 950 kc

T-1

=

Transformer GR 365-439

=

SO-1
PL-1

Socket H. B. Jones S-406-AB

=

Plug GE 39x370

DPST
DPST
DPST

A.H. and
A.H.
A.H. and H.

H.

81024BM

and H. 81024BM

81024BM

GR

376-L

PL-101 = Plug H. B. Jones P-406-RSE

1

=

Jack hec. Parts #1 Imp Jack

+++

+++

C-1

=

C-2
C-3

C-4
C-5

C-6

C-7
C-8

C-9

C-10
C-11
C-12
C-13
C-14
C-15
C-16
C-17

C-18
C-19
C-20
C-21
C-22
C-23
C-24

C-25
C-26
C-27
C-28
C-29

C-30
C-31
C-32
C-33
C-34
C-35
C-36
C-36A

C-37

C-38

C-39

C-40

C-41

C-42

C-43

C-44

C-45

C-46

C-47

C-48

C-49

C-50

0.25

=

1.0

=

0.02

=

0.8

=

0.8

=

=

175

=

0.01

=

1.0

=

0.005

=

0.005

=

0.01

=

0.00005

=

0.00025

=

0.01

=

1.0

=

13 -320

=

0.0003

=

0.00001 pf+10% CD Type4

=

0.00025

=

0.02

=

0.25

=

0.02

=

0.00001

=

0.25

=

0.25

=

6-100

=

0.0005

=

1.0

=

0.000470

=

4-50

=

0.000470

=

4 - 50

=

0.000470

=

4-50

=

4-50

=

20

=

0.25

=

0.25

=

0.000100

=

6-100

=

0.03

=

5 - 100

=

0.000100

=

2.0

=

0.01

=

0.01

=

100

=

100

=

100

=

100

C-51 = 200
C-101

=

=

=
=

=

=

=

=
=

6-100

0.000200

6 - 100

0.000200

0.0001

0.00005

1.0

4-50

0.000025

C-102
C-103
C-104
C-105
C-106
C-107

C-108

C-109
C-110= 4-50

C-111

=
=

=
=

=

0.000025

0.0001

0.0005
0,0005

0.00002

C-112
C-113
C-114
C-115

pf

+lo% Ind. Cond.

pf

510% Ind. Cond. 8232BAB

pf

+10%

pf

210% Aerovox

pf

510% Aerovox

Wf

pf

+lo% CD Type 4

pf

-10% Ind. Cond. 8232BAB

pf

510% CD Type 4

pf

+lo% CD Type 4

pf

?lo%

pf

510% CD Type

pf

510% CD Type 4

pf+10%
pf

:lo% Ind Cond. 8232BAB

ppf

pf

510% CD Type 4

pf

f10% CD

pf

+lo% CD Type 4

pf

:lo%

pf

510% CD Type 4

pf

510% CD Type 5W

pf

510% Ind. Cond. 8289BAB

pf

510% Ind. Cond. 8289BAB

ppf

pf

510% CD Type 4

pf

510% Ind. Cond. 8232BAB

pf

+l% Sickles ESC Silvercap**

ppf

pf

+1%

ppf

pf

+l% Sickles ESC Silvercap+

ppf
ppf

plf

55%

pf

+lo% Ind. Cond. 8289BAB

pf

El0% Ind. Cond. 8289BAB

pf

+5% Sickles ESC Silvercap

ppf

pf

510% CD Type 4

ppf

pf

55% Sickles ESC Silvercap

pf

510% Ind. Cond. 9235SARU

pf

+lo% CD Type 3L

pf
pf
pf
pf
pf

210% CD Type 3L'
+500/o,-10% Sprague DFP
+50%, -10% Sprague DFP

+50%, -10% Sprague DFP

+50%, -10% Sprague DI?P

pwf

+lo%

ppf

pf

+lo% CD Type 5W

ppf

pf

+lo% CD Type 5W

pf

+lo% CD Type 5W

pf

+lo% CD Type 5W

pf

210% Ind. Cond. 8341BAT

ppf

pf

510%

ppf

pf

+lo%

pf

+lo%

pf

510%

pf

+lo%

pf

+lo%

CD Type 4

GR 779-400

CD Type 4

CD Type4

Hammarlund MC -325S,

Ind. Cond. 8289BAB

Hammarlund APC Type C

Hammarlund APC Type C**

Sickles ESC Silvercap***
Hammarlund APC Type

Hammarlund APC Type C+
Hammarlund APC Type C++

COM-2OE

Hammarlund APC Type C
Hammarlund APC Type C

COM-2OB

Hammarlund APC Type C
Hammarlund APC Type C

Hammarlund

CD Type 5W

Hammarlund APC Type

CD Type 5W

CD Type 5W
CD Type 5W
CD Type
CD Type 5W

8289BAB

Y355
#355

locking

Type

(Part

of

APC

5W

4

a***

LC-4)

Type C

C

5W

+++Two 8200

51

210% REC-41BF in parallel

L-1

=

=

=

=

=

=

=

=
=

=

=

=

=

=

=

23.0

500

57.3

131.5

57.3

131.5

57.3

57.3
500
150
150

L-2

L-3
L-4
L-5
L-6
L-7

L-8
L-9

L-10

L-11

L-12

L-13
L-14

L-15

For 115 volt input

F-1

=

F-2

1.25

=

1.25 amp. Slow Blow 3AG GR FUF-1

For 230 volt input

F-1

=

F-2

0.6 amp. Slow Blow 3AG GR FUF-1

=

0.6 amp. Slow Blow JAG GR FUF-1

8

2.5

2.5

INDUCTORS

mh
mh
mh

GR 379-T
GR 1110-25

National Type R-100

GR CHA-3

mh

National Type R-100

ph

GR ZCHA-28

ph

GR ZCHA-20

ph

GR ZCHA-21)

ph

GR

~lh

GR ZCHA-21)

bh

GR ZCHA-20 Part

ph

GR ICHA-201

ph

GR ZCHA-28 - Part of LC-4

ph

GR

Part

ph

GR Part of

Of

FUSES

amp.

Slow Blow 3AG GR FUF-1

Part

of

Part of LC-2

of

}

ZCHA-24

LC-1

LC-3

TUBES

V-1

V-2

V-3

V-4

V-5

V-6

V-7

V-8

V-9

V-10

=

=

=
=

=

=
=
=

=

=

6AC 7
6SN7-GT
6SN7-GT FILTERS
6SJ7
6SA7
6AC7
6J5-GT
6J5-GT
5R4GY

GR

2LAP-430

Mazda S6

V-101 = RCA 6SN7-GT

V-102 = RCA 6J5-GT

V-103 = RCA 6SN7-GT

V-104 = RCA 9001

Wiring Diagram for Type

and Type

1110-A

1110

-

for 115K operation connect I

For 230V opxion connect P to

-

to_

3

ond

2 to

f

Interpolating Frequency Standard

-P1

Multivibrator

I

I

I

I

I

I

4

OSCILLATOR CRYSTAL

-

- - - - - - - - - - - - -

-

950kc

-MODULATOR

fc,

-

-

FlLrER

-1

'-----

11

I

Schematic Diagram for Type

U.cEFUL

HARMONICS

100- 200 MC

IMc INTERVALS

1110-A

and Type

1110-P1

TOP VIEW OF 1110-A

TOP

VIEW

OF

1110-PI

.

.

I

Div

=

10-

1110-A STANDARD 8 INTERPOLATOR

I

,

I

I'

MU1

1110-PI

TIVIBRATOR

USEFUL HARMONICS

0.1

Mc

INTERVALS

*

HE

T:

MCTER

FREQ.

Interior Bottom View of Type

1110-A

Interpolating Frequency Standard