Charles H. Callies Inc SC-II Complete Building Instructions
Society of Wireless Pioneers - California Historical Radio Society
Complete Building Instructions
For the SC-II
How to Build
the
SC~II Receiver
Authoritative Data on the 5-Tube Shielded Receiver
Designed by McMurdo Silver and
Laurence M. Cockaday
Containing Full Description, List of Parts, Wiring Instruc,
tions, Photographs and Detail,s of Assembly and Proper
Operation of This Remarkable Radio Receiver
l l I
TABLE OF CONTENTS
Section 1
What the S-C II Receiver Is ........ .. .............. ... .... Page 4
Parts Specified for the S-C Receiver . . ........ .. .. . ..... . .. Page 6
Inspecting and Testing Individual Parts .... .. ........... . .. Page 7
Assembling the Receiver .. .......... ... .. .. .. .. . .. . . ....... Page 11
Wiring .. . . . ... ..... . ...... .. ... . .. . .. ..... .... . . .. ..... . . . Page 15
Checking Connections . .. . .... .. ...... .. .............. . .... Page 20
Attaching Link Motion ...... . ... .. . ... . . . . .... . . . .. . ... . ... Page 22
Mounting Front Panel .. . .... .. . .. ... ..... ..... . ...... .. .... Page 23
Attaching Dials .. ..... . ... . ... . . .. ... . ... .. . . .... . . .. ... . .. Page 23
Coil Placement .. .. . . .. .. . ........... . ... ... . .. . . ... .... .. .. Page 24
Preliminary Testing .. .. .. .. .. • • ... .. . ....... . .. . . . .. ... . . . . Page 26
Connecting Batteries ............ . ......... . .. . ... . ......... . Page 27
Antenna and Ground System ..... .. ... .. ... . .. ... .. . .. . . • • . Page 27
Loud Speaker .. .. .... .. . . .... . . . . .. .. . . . .. ..... . .. .... . . ... Page 30
Operation .. . . ... . .. • • .. . ...... . ......... .. . . . .. ........... Page 30
Most Sensitive Operating Condition . . . .. . . . . .............. . Page 32
Tuning for Distant Stations . . .... .... .. ............ . .. . •• .. Page 32
Loggin;; .. . ... .. .... ..... . . . ..... . .. .. ...... . ... . . .. ... .. .. Page 33
Preliminary Selectivity Adjustment .. .... ... . • • . ............ . Page 33
Balancing ........ . . . .... . . . .... . . .. .... . .. . . . . .. . .. .. . . .... Page 34
Battery Eliminators .. ... . .... ... . .. .... . . .. .. . . • • . .. . .. . ... Page 36
Section 2
Trouble-Shooting
Failure to Receive Signals, Lack of Volume , Lack of
Sensitivity , Poor Tone Quality . . ... ... . .......... ...... Page 37
Noisy Reception, Blocking or Motor Boating, Humming ... . Page 38
Batteries, Current Consumption , Loud Speaker, Fitting
Shields in Place, Coil Placement .... . ..... . . .. ... . ...... Page 39
Tubes, Use of UX200A Detector Tube, Potentiometer
Switch , Coil Socket Contact . ..... . ... . . .... ...... .. .. .. Page 42
Selectivity Adjustment , Loop Operation Short and
Long Wave Reception, Condenser Adjustment . ... ...... Page 43
Automatic Control of Power Equipment ........... . ... . . ... Page 45
Copyright 1927
Charles H. Callies Inc.
846 W. Jackson Blvd.
Chicago
HE S-C II receiver has been designed by Lauran ce M. Cock-
T
aday and M cMurdo Silver with the idea of pro viding a radio
receiver possessed of practically all the mechanic al and electrical
detail s of the finest factor y-built receiver plus a quality of reproduc-
tion not obtainabl e in any except the most expensive of factory products.
The S-C II receiver will provide sufficient volume for home enter-
tainment purposes, and even for a small auditorium upon local sta-
If reception conditions are favorable, stations several hundred
tions.
or more miles away may be received with ample loud speaker volume.
The quality of reproduction obtainable is believed to be superior to
that of practicall y all other receivers with the exception of a very few
of the highest class receivers price at from
The sensitivity of the receiver is sufficient to allow the reception
of out-of-town stations with pleasing regularity and its selectivity is
sufficient to permit of separation between powerful local stations in
such crowded areas as those encountered about New York or Chi-
cago. At the same time, the operation of the receiver is simplicity
itself, for only two tuning controls need be manipulated together
with a single small knob used to turn the receiver on and off and
adjust volume.
The receiver itself is easy to assemble since every detail of its con-
struction has been planned with the utmost care, with the thought
in mind that it would be assembled by an absolute novice, totally
unfamiliar with radio. At the same time, investment value has been
considered most carefully and it is believed that the S-C II receiver
will not become antiquated for some years to come since its design
is in accordance with best engineering practices and there seem to
be few ways in which it could be practically improved upon. Nevertheless, should broadcasting conditions change, as in the matter of
wavelengths employed, the S-C II receiver is so flexible that by a
simple alteration of the coils used, or the substitution of a new set
of coils, its wa velength range may be adapted to any particular
of broadca sting service that might be anticipated within the next
few years.
While it is very true that many five-tube factory-built receivers
may be obtained upon the open market for figures as low as
the purchaser should always remember that in radio, as in other
fields, he only too frequently receives exactly what he pays for
( often less) , and it is hardly to be believed that a factor y-built
receiver, bearing as it must factory overhead and labor, can contain
$250.00 up.
class
·
$25.00,
[ 2 l
[ 3 l
the same value either in material or engineering design that is obtainable in a receiver constructed by the user and costing
many of the more reasonably priced commercial receivers. Thus ,
were the S-C II receiver to be supplied as a completely assembled
outfit , and were it to be priced on a level with average factory-built
sets, it would cost approximately
few hours of enjoyable work in building it himself , the purchaser is
able to save approximately
is able to obtain approximately double value for an expenditure of
$60.00 for the S-C II receiver that he would receive m a
about
factory-built set.
$60.00. To state this in another way, he
$120.00; whereas by virtue of a
more than
110
What the S-C II Receiver Is
HE S-C II receiver is a five tube set of standard design , incor-
T
porating two stages of tuned
detector, and two stages of
The design of the radio frequency amplifier is such that it may be
adjusted to peak efficiency for each wavelength received , no endeavor
being made to provide semi-automatic means of holding it at a point
just below peak efficiency for all wavelengths. (
fact that this could not be accomplished practically due to variations
in receivers, and to obtain stability it would be necessary in an automatically stabilized system to accept something less than peak sensitivity.
means of one small volume control knob, the set may be adjusted
to the absolute limit of sensitivity and, literally, nothing in the way
of performance be sacrificed as a result.)
"0,"tuned by a variable condenser
will cover the wavelength range of
the use of either a long or short antenna. This first RF stage includes
a
ond radio frequency transformer "P-1," the secondary of which
(similar to that of the antenna coil "O"), is tuned by a second
variable condenser
former "P-1" with its socket
is housed in a complete aluminum box "Q-1" which effectually prevents the transfer of undesired energy between this stage and
other portion of the receiver and also eliminates the pick~up of
extraneous interference upon the coils, condensers, and wiring of the
stage itself. This second stage, incorporating also a
leads into the detector stage, similarly designed and constructed, and
housed in the second aluminum shield "Q-2."
In the S-C II receiver no compromise has been made, and by
The first radio frequency amplifier consists of an antenna coil,
UX201A tube, the plate circuit of which is connected to the sec-
"I-2." This second RF stage, consisting of trans-
"L-2," condenser "I-2" and tube "M-2"
~adio fr~quency. amplifi<:atioI?, a
high quality audio amplification.
It is a well-known
"I-1," and so designed that it
200 to 550 meters, and allow for
any
UX201A tube,
[ 4 l
~
'
~
' '
'
"
'(~@
"
~
~
0
.
@
r
•
1
I>
The sensitivity of the radio frequency amplifier as well as the
volume, is controlled by means of a 200-ohm potentiometer "B,"
integral with which is an on-off switch which completely turns the
receiver on and off.
The detector tube employs a negative grid bias to permit rectification, for it is well known that a grid bias will allow of the handling
of stronger signals without distortion than will a grid condenser
and leak.
The output of the detector tube is fed into an audio amplifier
consisting of two audio transformers "N-1" and "N-2," a CX301A
and a CX371 tube. The audio amplifier is extremely interesting and,
in a sense, original, for its frequency range is from 30 to approximately
5,000 cycles, above which frequency it provides practically no amplification. This is desirable since the radio frequency portion of the
receiver preceding the audio amplifier is designed to pass a 10 kilocycle band, which means that after rectification only frequencies up
to 5,000 cycles ( the range of frequencies employed in music and
speech is from about 27 to 4,192 cycles), will be fed from the detector to the audio amplifier. However, the very sharp cut-off above
5,000 cycles of the audio amplifier results in the elimination of background hiss, and possibly more important, heterodyne squeals frequently heard in present-day broadcasting when some 600 stations
are simultaneously operating in channels which will accommodate,
at the most, only one-third this number of stations without pronounced interference.
The S-C II receiver is designed for operation with either batteries
or battery eliminators and will be found quite satisfactory when so
used. It may not satisfactorily be used with dry cell tubes, for the
vQlume obtained, as well as the quality, will not be comparable with
that obtained with standard CX301A and CX371 tubes. (It must
ee understood that the receiver will operate satisfactorily with CX299
and 220 tubes but that the volume and quality will suffer as a result
of their use.)
Parts Specified for the S-C II Receiver
LIST
A
B
C-1-C-2
D
E-l-E-10
1 Carter H
1 Carter M-200-S potentiometer. . . . . . . . . . . . 1.25
2 Carter tipjacks @ 10c................... .20
1 Benjamin No. 9040 UX spring socket...... .75
10 Eby binding posts (Ant., Ant., Gnd.,
¾ resistor ..................... $0.25
A+,
[ 6 ]
A- C-, C-, 45+, 90+, Amp.+) @15c. 1.50
F-1-F-2
G-1-G-2
H
I-1-I-2
J
K
L-1-L-3
M-1-M-4
N-1-N-2
0
P-1-P-2
Q-1-Q-2
R-1-R-2
*With the panel and chassis will be found an envelope containing:
2 National B vernier dials, clockwise @ $2.50. 5.00
2 Polymet
1 Polymet .002 condenser. . . . . . . . . . . . . . . . . . .40
2 Silver-Marshall 316B condensers @ $4.50 .. 9.00
1 Silver-Marshall 316A condenser ........... 4.50
1 Silver-Marshall 637
3 Silver-Marshall 515 coil sockets@ $1.00 ... 3.00
4 Silver-Marshall 511 tube sockets@ 50c .... 2.00
2 Silver-Marshall 220 transformers @ $6.00 .. 12.00
1 Silver-Marshall 116A coil . . . . . . . . . . . . . . . 2.50
2 Silver-Marshall 118A coils @ $2.50 ....... 5.00
2 Silver-Marshall 631 stage shields @ $2.00. . 4.00
1 Van Doorn* S-C chassis unit ( including
pierced formed steel panel, chassis and nuts,
screws and insulators) ................... 5.00
31 6/32 nuts
22 6/32 x
9 6/32 x
9 collars
20 Belden soldering lugs
20 binding post insulating washers
4 tipjack insulating washers
3 potentiometer-switch insulating washers
1 mf. condensers @ $1.00. . . . . . . . 2.00
_link motion ........... 2.00
¾" RHN P screws
1 ¾" RHN P screws
¾ x ¾"
$60.35
Inspecting and Testing Individual Parts
ROM the foregoing general description of the parts used in
F
the S-C II receiver, the builder should have become sufficiently
familiar with them so that he may be able to intelligently inspect
each part before attempting to assemble the receiver.
Resistor "A" is a small strip of fibre wound with a flat resistance
wire, connections to which are made through two mounting lugs on
either end. Unless it appears to be physically broken or damaged, no
trouble may be anticipated.
Potentiometer-switch "B" should be examined very carefully. It
will be seen to consist of a
wire held in a metal frame. As the knob is turned a contact arm
moves over this wire-wound resistance strip and it is necessary that
this contact be so bent that it presses firmly against the resistance
sector at all points throughout its arc of rotation. The on-off switch
fibre strip wound with fine resistance
[ 7 l
simply consists of two contacts carried on a met al frame attached to
the pot entiometer. The under or inside contact is actu ated by a fibre
cam attached to the potentiometer contact arm shaft. An angular
bend in this inner arm will be seen to fall into the bakelite cam at
one setting of the potentiometer adjustment. This is corr ect, and at
this point the under switch spring should not press against the outside switch spring. As the shaft is rotated, the angular bend in the
spring will be forced out of the slot in the bakelite cam and as this
occurs it will be seen that the cam forces the inner conta ct of the
switch against the outer conta ct blade and this condition of the two
springs pressing against each other should persist throughout the balance of rotary movement of the potentiometer shaft. (Wh en the
angular bend of the under contact arm is allowed to fall into the
ia the bakelite cam, the on-off switch is open-at other positions
slot
it is closed.) Should the springs not make proper contact, they should
be bent with the fingers so that they make firm solid contact, and care
should be taken to see that the actual points of contact are clean,
and free of dirt or dust.
Tip jacks "C-1" and "C-2" may be ignored until the receiver is
completely assembled, at which time they should tightlv hold the tips
lou·d speaker or phone cord inserted in them. If they do not, the
of
springs may be bent so that they will do so.
Detector
tube socket "D" should be examined to see that the four
terminal screws and nuts are quite tight and a tube tried in it to make
sure that proper contact is effected and that the socket springs hold
the tube tightly in place.
Binding posts "E-1, E-2, E-3 , E-4, E-5, E-6, E-7, E-8, E-9, E-10"
should be examined to see that they have the proper markings, that
they are equipped with fastening nuts , and that their tops unscrew
and screw up properly so that a wire may be held between the top
and base of each binding post.
Dials "F-1", and "F-2" should be examined to see that the indicator plates rotate as the control knobs are turned and that each one
is accompanied by the three small studs and nuts necessary to fasten
it to the panel.
Fixed condensers "G-1" and "G-2" should be examined for signs of
physical damage and should preferably be tested with a B battery.
If a B battery is available, and two wires from it are connected to
the two terminals of the condenser, a spark should be noticed. With
battery leads removed, the two contacts of the condenser should be
short-circuited with another piece of wire , when it will ,be noticed
that the charge given to the condenser by the battery will discharge
with a slight spark.
[
s J
Gz
"'
.J
L3
lz
...
Lz
Q,
Fig 2.
[ 9 l
d
Condenser "H" should be tested in the same fashion except that
being very small it will not retain a charge and will simply show no
spark as connections from the battery are made to it.
The variable condensers "I-1," "I-2" and
to see that they rotate properly and that the rotor plates do not touch
the fixed or stator plates at any point thruout their arc. Should
condensers have been damaged in transit, they may be adjusted ac-
cording to instructions appearing elsewhere in this booklet.
Mechanical link motion
being bent, can be ignored until the time comes to assemble it on
condensers.
Coil sockets "L-1," "L-2" and "L-3" should be tested in connect ion
with the RF transformers "O," "P-1 " and "P-2." Each transformer
should be inserted in a coil socket and the following test for continuity of winding made. Taking RF transformer "O" in its coil
socket, one lead from the B battery should be touched to terminal
6 and held there. The other lead from the B ,battery should be
touched successively to terminals Nos. 3, 4, and 5, from which a spark
should be obtained. In the case of transformer "P-1" and "P-2" a
spark should be obtained between contacts 3 and 6, and 4 and 5, but
not between 3 and 4 or 5.
the coil sockets should be examined to make sure that the spring fin-
gers touch the buttons on the coil forms.
Tube sockets "M-1, M-2, M-3, M-4" should be tested as
detector tube socket "D."
The two large transformers "N-1" and "N-2" should be tested
with a B battery. A spark should be obtained between terminals
and 2, and 3 and 4, but not between terminals 1 and 3 or 4. No spark
should be obtained between any terminals
instruments.
Unless the shields "Q-1" and "Q-2" appear to be bent or crushed,
they are OK; assuming the base pans to be pierced and the front
ends of each shield to be slotted with a long U-shaped slot.
The steel panel and chassis "R-f' and "R-2" should be examined
to see that they are not scratched and that they appear to be properly
pierced and formed, but not bent thru damage in transit.
"K," unless it shows obvious signs of
If a spark is not perceived in this test,
[ 10 l
"J" should be examined
the
the
No.
was
an_d the metal cases of the
1
Assembling the Receiver
j\ LL parts for the receiver having been procured, and tested in
f"l.. accordance with the foregoing paragraphs, the assembly may be
started by mounting all parts upon the steel chassis "R-2" in accordance with the photograph of Fig. 2. The first step is to put all
binding posts and tipjacks in place.
screws, washers, etc., accompanying the chassis, there will be found
ten small
enough to slip over the binding post screws. There will be found
ten more similar washers with small projections on one side which
are designed to be put into the over-size holes at the rear of the steel
chassis for the binding posts. The nuts having been removed from the
binding posts, they should be placed on the chassis in position shown
with the extruded washers on top of the chassis and the
beneath, with the extrusions of the upper washers falling inside the
holes of the chassis.
are screwed up upon the binding post shanks with a pair of pinchers,
none of the metal of binding post shanks will come in contact
the chassis, but will be held away from it by the insulating washers.
Under each binding post nut should be placed one of the small soldering lugs, exactly as seen in the photograph of Fig. 3.
fashion as the binding posts, using the set of four ( two plain and
two extruded) insulating washers that appear to be slightly larger
than those used for the binding posts. The details of attaching these
tipjacks will be seen from the photograph. ( Being of metal, they
must not actually touch the metal chassis.)
the front of the chassis with its various contacts projecting upward,
as seen in the different photographs. The knob having been removed
from this instrument, the lock nut on the shaft bushing should
be unscrewed. Three large insulating washers will be found accom-
panying the chassis screw assortment. The two plain ones should
placed over the shaft bushing and pushed back. The shaft bushing
should then be pushed thru the hole in the half-round projection
the front of the chassis, the extruded washer placed over the bushing
so that the extrusion falls in the hole of the chassis, and the lock nut
screwed up on the whole assembly. When this operation
formed properly a test should be made with a B battery . One wire
from the B battery should be touched to the chassis and the other
touched to all contacts of the switch and
flat insulating washers of fibre with holes in them just large
If this is done, it will be seen that when the nuts
The two tipjacks should be attached to the chassis in the
The on-off switch and potentiometer, "B," should be fastened to
In the small package of assorted
flat washers
with
same
also
be
at
is per-
potentiomett>r. If the in-
[ 11 l
sulating washers are properly arranged and there is no metallic contact between the chassis and unit "B," no spark will be
obser~ed,
which is the correct condition. (The same test should be given the
binding
posts and tipjacks, for there must be no metallic contact between any of these instruments and the chassis at this stage of the
assembly.)
The next step is to mount the two stage assemblies in shield pans
at the right-hand end of the chassis. By placing the shield pans in the
approximate positions shown in the photographs, it will be found
that certain holes will coincide-notably, the large round lead hole
to the rear of each shield pan, plainly visible in Fig. 2, as
well as the two mounting holes for the tube socket, the three holes
for the coil sockets, and those for the condensers "I-2" and
"J."
In the screw assortment will be found a total of nine hollow studs
and nine long screws. Taking coil socket "L-3" three long screws
should be pushed thru the mounting holes in it and over these screws
on the under side of the coil sockets the three hollow studs for this
socket should be slipped. The socket should then be placed in position in shield pan "Q-2" as seen in the various photographs. On the
under side of the chassis, nuts should be tightened up on these mounting screws with a pair of pinchers. When the operation is completed, the coil socket will be held in place
shield pan "Q-2" by means of the three mounting screws and the
three hollow studs on the mounting screws. The actual arrange-
ment of these studs may possibly be most dearly perceived from the
photograph of Fig. 4. The same operation should be performed with
coil socket "L-1" and "L-2" ( the shield pan "0-1" being held to the
chassis "R-2" under coil socket "L-2.") Caution should be observed
in every case to make sure that the small indentation in the bakelite
coil socket ring falls in the position visible in photograph of Fig. 2
and that terminal No. 3 of the coil socket is in every case the extreme
right-hand terminal, viewing the chassis from the front.
¾ of an inch above the
H
E,o
Ee
a,
E,
E~
A
Es
Ea
E,
c,
c,
The next step is to mount the detector socket "D." The details of
this operation are evident in Fig. 2. A single screw is pushed thru
the mounting hole located close to terminal "G" of this coil socket.
Under the screw head is placed one of the small lugs and a nut is
tightened up with a pair of pinchers on the end of the screw projecting thru the under side of the chassis. Socket "D" is held in
place by this single screw and in order that contact be made by means
of the wire shown connecting the minus terminal of this socket to
[ 12 J
Fig. 3
[ 13 l
the lug under the mounting screw head it is necessary that the bottom of the chassis be cleaned of enamel where the fastening nut
makes contact with it.
The four tube sockets "M-1, M-2, M-3, M-4," may be mounted
using two screws and two nuts each. Under the mounting screw
heads, falling between the minus and plus terminals of these sockets a
soldering lug should be placed, turned toward the minus terminal.
Another soldering lug fastened under the "minus" terminal screw
of each socket is pointed toward the first lug , as can be seen from
Fig. 2, so that both lugs touch. (They are later soldered together
and make the minus connection between each tube filament and the
chassis which actually forms the negative A and negative B battery
wiring for the receiver.) It is needless to say that the under side of
the chassis should be scraped where the nuts for these mounting
screws come in contact with it.
Referring to Fig. 3, it will be seen that some of these mounting
screws serve to hold the condensers and fixed resistances on the bottom of the chassis. Thus on the mounting screw holding tube socket
"D" condenser "H" is fastened by means of another nut tightened
up on this screw to hold the condenser firmly in position. It is very
important that this procedure be followed out exactly-one nut must
serve to hold the condenser away from the actual chassis while
another holds it tightly to the screw. (To rephrase, it is necessary
that the metal contact clamps of condenser "H" do not actually
touch the ohassis at any point but that thru the eyelet holding one
of these clamps in place the mounting screw of coil socket "D" is
passed with a nut on either side of the condenser.) Upon the mount-
ing screws of sockets "M-1" and "M-2" are fastened to two bypass
condensers "G-1" and "G-2."
the metal cases of the condensers make contact with the chassis, and
they are clamped directly to it by the fastening nuts on the tube
socket mounting screws. Upon the rear mounting screw of coil
socket "L-2'' one end of the half ohm resistance "A" is held in the
same fashion as was condenser "H": that is, as the screw comes
thru the bottom of the chassis "R-2" one nut is placed over it and
screwed up tightly; then one end of the resistance "A" is dropped
over the screw and a second nut tightened up on top of this, so that
at no point does any of the metal structure of resistance "A" come
In this instance it is desirable that
in contact with chassis "R-2."
The two audio transformers "N-1" and "N-2" should be fastened
on the chassis at the left-hand end as shown in Fig. 2. The exact
position of these transformers is evident from the photograph, and it
[ 14 ]
will be seen that the terminal strip of the rear transformer is toward
the right while that of the front transformer is toward the left.
The three variable condensers "I-2," "I-1" and
fastened to the chassis. In the postions shown in Fig. 2 "l-1" (which
is identical actually to "I-2") falls at the left of the chassis exactly
in front of coil socket "L-1." Two mounting holes will be found
the chassis, the position of which coincides with the two threaded
holes in the mounting feet of each condenser. Screws should
pushed up thru the chassis and screwed up tight into the mounting
lugs of the condensers. (The screw-heads may be
Condenser
chassis, in shield pan "Q-2."
The assembly is now completed, and should be carefully examined
and checked, making sure that all instruments are mounted exactly
as seen in the photographs.
J, with the shortest shaft, mounts at the nght end of the
"J" should be
be
s~en in Fig. 3)
Wiring
HE wiring of the S-C II may be done entirely without solde~-
T
ing,
if desired, although it is strongl_y ~ecommende~ ~hat certam
connections
where soldering is not employed will be given; for any
builder not familiar with the use of a soldering iron had best take his
parts to a service station, where he may have his receiver assembled
and tested at a very nominal cost.)
All wiring on top of the chassis should first
ing
as follows: One end of the fabri~ insulated ~ellogg hook::-~p
wire should be bared for about half an mch by pushmg back the msulation and this end twisted around terminal "G" of the coil socket
"D." The nut on
clamping the wire tightly to the terminal. The
straight forward on the chassis, scraped free of msulat10n so that 1t
may ,be twisted around terminal screw N ?· 3 _of coil. socket ''.L-3."
This screw being tightened upon the wire, 1s continued directly
forward t~ a soldering lug found under a nut on condenser "J."
The end of the wire is pushed thru this lug, twisted around it, and
soldered to the lug. This connection is plainly illustrated in Fig. 5,
where the wire joining these three terminals can be seen.
A similar connection is made joining terminal .
"M-2," to terminal No. 3 of coil socket "L-2," to
condenser "I-2."
An exactly similar connection is made between terminal "G" of
be soldered. (No descnpt10n of the wmng method
prospectiv:c
be put in place start-
thi~ terminal is tightened up with a pair of pinchers,
_wire i? then pulle~
"Q" of tube socket
th_e soldering lug on
[ 15 J
in
tube socket "M-1 ," terminal No. 3 of coil socket "L-1 ," and the
soldering lug on condenser "I-1."
These three exactly similar leads are plainly visible in Fig.
and should be as short and direct as possible.
A small wire should now be used to connect the minu s terminal
of coil socket "D" to the lug under the mounting screw head of this
socket, exactly as seen in Figs. 2 and 5.
The two overlapping soldering lugs on the "minus" terminals and
the mounting screws adjacent to these terminals in the case of tube
sockets "M-1, M-2 , M-3 , M-4" should be soldered together exactly
as illustrated in Fig.
2.
Starting now at the left end of the chassis, terminal "G" of tube
socket "M-4" should be connected to terminal No. 3 of audio trans-
former "N-2." Terminal No. 2 of audio transformer "N-2" should
be connected to terminal "P" of tube socket "M-3." Terminal "G"
of tube socket "M-3" should be connected to terminal No. 3 of audio
transformer "N-1."
One end of a long wire should be fastened under the plus
terminal of tube socket "M-3," then carried over, kitty-cornered,
9Craped and fastened under terminal "plus" of tube socket "M-4." In
the chassis adjacent to this terminal will be found a hole thru which
the long end of this connecting wire should now be pulled. Turning
to Fig. 3, it is practically impossible to see where this wire comes
thru the chassis (the approximate point is marked at "X"), comes
out underneath and follows the path of other connecting wires (which
will later be put in place) . This wire is pulled taut on the under side
of the chassis and up thru the large hole adjacent to the "plus"
terminal of socket "M-1" at which point the wire is scraped , wrapped
around and fastened under terminal screw "plus" of the tube socket
"M-1," and finally pulled back down under the chassis thru the same
large hole thru which it come up. It is then drawn slightly to the
rear of the chassis around the corner of condenser "G-2," scraped and
soldered to the lug of binding post "E-4" and then carried straight
along to a similar large hole in shield pan "Q-1" adjacent to terminal
"plus" of tube
sock:et "M-2." At this point it is scraped exactly as in
the case of the previous tube socket, fastened under terminal "plus"
of socket "M-2" and pulled back down thru the hole in the chassis
thru which it came up. Again it is carried along the
back: of the
chassis, this time behind condenser "G-2" and up thru the last of the
large holes, this time found in shield pan "Q-2" just under the
"plus" contacts of tube socket "D." The wire is here clipped, the
l 16 I
5
J
D
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[ 17 l
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