Hammarlund SP-600-J User manual

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GENERAL PURPOSE'
COMMUNICATIONS RECEIVER
MODEL SP-600-JX·
AND
MODEL SP-600-J
INSTRUCTIONS
ISSUE 3 - APRIL 1952
Manufactured by
THE HAMMARLUND MFG. CO. INC.
460 West 34th St. New York 1, New York, U.S.A.

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sp-600-JX and sp-600-J INSTRUCTIONS ISSUE 3
PAGE 22 Parts List, Symbol Designation L46
Description
Part No.
Reads
R.F. Choke, 3.5 microhenrys
Should read R.F. Choke, 12 microbenrys
Reads 15615-Gl
Should read 15615-2
PAGE 33-34 Oircuit Diagram, Symbol L46 (in T6)
Value reads - 3.5 ph
Should re ad -12 ph
PAGE 35-36 Connection Diagram, Symbols C140 and cl64
Reads 0140
Should re ad 0164-
Reads C164
Should read c140

GENERAL PURP·OSE
COMMUNICATIONS RECEIVER
MODEL SP-600-JX
AND
',MODEL SP-600-J
INSTRUCTIONS
MODEL SP-600-J
The Model SP-600-JReceiver does not have the
Frequency Control Unit. When this Instruction
Book is used in connection with the Model SP-600-J
Receiver, all indications
in the text, photographs
and diagrams, with reference to the Frequency Con-
trol
Unit, should be ignored as they do not apply.
With this exception the two models are identical.
ISSUE 3
Manufactured by
THE HAMMARLUND MFG. CO. INC.
460 West 34th St. New York 1, New York, U.S.A.
Printed in U. S. A.

F\G. \
FRONT VIEW OF RECEIVER
Sp- 600-JX IN CABIN ET

Title
Technical Summary
TABLE OF CONTENTS
Page
4
IGeneral Description 5
II Circuit Description 6
III Installation 7
IV Operation 8
V
Maintenance 10
VI Alignment 16
VII Conversion of Table Model Receiver for Rack Mounting. .................................... .. 20
Table I-Tube Socket Voltages .. '" '" . . . . . .. . .. .. . .. .14
Table 2-Tube Socket Terminal Resistances '" " ........................ .. 15
Table 3-RF and HF Oscillator Alignment Frequencies. ............................................ 17
Table 4-Approx. Signal Inputs at IF and AF Stages. .............................................. 17
Table 5-Parts List
ILLUSTRATIONS
21
Figure
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure
11
Figure 12
Figure 13
Figure 14
Figure
15
Figure 16
Front View of Receiver SP-600- ]X, in cabinet. ........................................... 2
Block Diagram 7
Location
of Tubes and Adjustments , 18
Audio and Overall Fidelity Curves ,............ .. . . . . . . .. 18
Selectivity
Curves -. . . . . . . . . . . . 19
Rear View of Receiver. ............................................................ .. 25
Top View of Receiver. ............................................................. .. 26
Top View of Receiver-Capacitor Shield and Spare Fuse Cover Removed. ................. .. 27
Bottom View of Receiver-Tuning Unit Shield Removed. ............................... .. 28
Bottom
View of Receiver SP-600-]X. ................................................. .. 29
Bottom
View of RF Tube Platform. .................................................. .. 30
Bottom
View of Frequency Control Unit. ............................................. .. 31
Circuit Diagram of Receiver. ........................................................ .. 33_
Connection
Diagram-Receiver Chassis. .............................................. .. 35
Connection Diagram-Tuning Unit. ................................................... 37
Connection Diagram-Frequency Control Unit.......................................... 39
[ 3 ]

GENERAL PURPOSE COMMUNICATIONS RECEIVER
MODEL SP-600-JX
TECHNICAL
SUMMARY
Electrical Characteristics
Frequency Range-total 6 bands .
Band 1 .
Band 2 .
Band 3 .
Band 4 ...................................•.•.................................
Band 5 .
Band 6 ' .
.54 to 54.0 mc
.54
to 1.35 mc
1.35
to 3.45 mc
3.45
to 7.40 mc
7.40
to 14.8 mc
14.80
to 29.7 mc
29.70 to 54.0 mc
Power Output-2.0 watts, with less than 10 percent distortion.
Output Impedance-600 ohms-balanced split windings.
Phone jack-winding; delivers 15 milliwatts to an 8000 ohm resistive load, when the audio output to the
600 ohm power load is adjusted to 500 milliwatts.
Power Supply Requirements
Line Rating........................... 95,105,117,130, 19Q, 210, 234 and 260 volt taps, 50-60 cycles.
Power Consumption. ................................. 130 watts, 1.25 amps. at 117 volts-maximum.
Tube Complement-total 20
RF, IF and BFO Amplifiers , " 7 - 6BA6
HF, 2nd Conversion and BFO Oscillators 3 - 6C4
Crystal Controlled
HF Oscillator. ................................................... .. 1 - 6AC7
Mixers :..................................................................... 2 - 6BE6
Detector,
"C" Bias Rectifier and Noise Limiter &' Meter Rectifier. ..................... .. . .. 3 - 6AL5
AF Amplifier and IF Output. 1 - 12AU7
Power Output. " 1- 6V6GT
Rectifier '. . . . . . . . . . . . . . . . . . . . . . . . .. ..... .. 1- 5R4GY
Voltage Regulator. ................................................................ .. 1 - OA2
Mechanical Specifications
Rack Mode1- Dimensions; 19 inches wide, 10J/z inches high and 16J/z inches deep from rack mounting
surface. Weight 66 lbs.
Table Mode1- Dimensions; 21% inches wide, 12 ~ inches high and 17!/s inches deep. Weight 87J/z lbs.
Performance Data- (approximate values-taken on asample receiver)
Sensitivity is 2.3 microvolts,
or better, throughout the entire frequency range, for asignal to noise ratio of
10 db, at 20 milliwatts output and with the RF Gain Control at maximum.
Image rejection ratios are
better than. 74 db throughout the frequency range.
The IF rejection ratio at 6(')0 kc is 2700 to 1.
The A VC action will maintain the output constant within 12 db when the input is increased from 2to
200,000 microvolts.
[ 4 ]

GENERAL PURPOSE COMMUNICATIONS RECEIVER
I
GENERAL DESCRIPTI'ON
The SP-600-]X is a20 tube Radio Communications
Receiver
with self contained power supply. The]
suffix in the model number denotes that this receiver
is made using components
having characteristics which
are the equivalent of military component specifications
insofar as is practicable.
The receiver is supplied in either awell ventilated·
steel, table model cabinet finished in
dark grey to
complement the lighter grey front panel or for mount-
ing in a standard 19 inch relay rack.
The self contained power supply is designed fo~
operation from asingle phase, 50 to 60 cycle alternat-
ing current power source. The power transformer
primary is provided with taps covering aline voltage
range from 90 to 270 volts. The power consumption
is 130 watts.
The receiver is suitable for either headphone or
loudspeaker reception of AM radio telephone, CW
telegraph, AM MCW telegraph signals and for
diversity applications.
The standard model provides continuous coverage
over afrequency range from 0.54 to 54.0 megacycles
in six bands. The large easily operated band change
control knob,
on the front panel, selects the desired
frequency band and a band indicator visible through
asmall front panel window indicates the frequency
band in use. This control also aligns the dial frequency
indicator with the proper dial scale.
In addition to the frequency scales, the main dial
has an arbitrary scale which in conjunction with the
vernier dial provides continuous expanded scales over
each frequency band for extremely accurate logging
and resetability.
The single tuning control is large and of special
design
to permit maximum traverse speed as well as
exceptional
operating ease. It controls both the main
and vernier dials. An anti-backlash gear train provides
extremely close calibration accuracy
and completely
accurate resetability. A
tuning lock provides positive
locking action
without affecting the frequency setting.
The tuning ratio from the tuning control to the
main dial is 50 to 1 and the ratio from the vernier dial
to the main dial is 6 to 1.
Two stages of radio frequency amplification are
provided
on all bands. Single conversion is used for
signal frequencies up to 7.4 mc and double conversion,
employing acrystal controlled oscillator,
for signal
frequencies above 7.4 me.
Four stages of IF amplifica-
tion, detector and A VC rectifier, noise limiter and
. meter rectifier, beat frequency oscillator and buffer
[ 5 ]
amplifier, IF output, AF amplifier and output power
stage are provided.
The frequency control unit provides for fixed
channel crystal controlled operation on any six fre-
quencies within the range from .75 to 54 mc. Front
panel. control~ permit the selection of the normal high
stabIhty contInuously variable tuning or either of the
six selected fixed frequency signals. For crystal con-
trolled fixed channel operation it is only necessary to
set the dial to the signal frequency, switch to the
crystal frequency desired and tune with the delta
frequency cor:trol.
These crystals are not supplied
WIth
the receIver, but may be purchased on special
order from HAMMARLUND MFG. CO. specifying
the signal frequency for which each is to function.
The noise limiter circuit effectively limits the inter-
ference from ignition systems or other sources of pulse
type noise. The limiter switch permits optional use
of the limiter.
The antenna input circuit is designed for use with
abalanced line. The input impedance is nominally
95 ohms. The receiver may also be operated with a
conventional single
wire antenna.
The audio output circuit is designed for a600 ohm
load or line and is provided with a four terminal split
WIndIng
for balanced load operation. Maximum power
output is approximately 2.0 watts. The headphone
circuit when referred to an 8000 ohm load provides
signals
attenuated approximately 15 db below the 600
ohm power output.
The send receive switch desensitizes the receiver
b.ut leaves
the power on to provide for instant recep-
tIOn between transmission periods.
Radiation is negligible
and complies with require-
ments for shipboard operation and for multi-receiver
installations.
Frequency drift after a 15 minute warm up period,
ranges
between .001 percent and .01 percent of fre-
quency depending on the frequency used. This is a
very
unusual degree of frequency stability for variable
tuned HF oscillators and closely approaches crystal
stability.
The selectivity control provides three degrees of
crystal and three degrees of non-crystal selectivity
ranging from sharp (.2 kc) to broad (13.0 kc). The
crystal filter embodies the same circuit features that
have proved so effective and desirable in Hammar/und
Super Pro Receivers, incorporated in an improved
mechanical
design .

II
CIRCUIT DESCRIPTION
General- The circuit is shown schematically in
Figure 13. Ablock diagram, Figure 2, is provided to
more clearly show the arrangement and functions of
the various circuit sections. The location of the various
tubes is shown in Figure 3. The circuit, for single
conversion,
used for signal frequencies up to 7.4 mc
consists
of two stages of RF amplification V-I and
V-2, First MiXer V-5, First Heterodyne Oscillator V-4,
four stages of IF amplification V-7, V-9, V-10 and
Vll, Detector and AVe rectifier V-14, Noise Limiter
V-15, Beat Frequency Oscillator V-13, IF output and
AF amplifier V-16-A and V-16-B, Output Power stage
V- 17 and the Power Supply system which includes
B
Power Rectifier V- 19, CBias Rectifier V-20 and
Voltage Regulator V-18.
In the circuit for double conversion, used for signal
frequencies
above 7.4 mc, the Second Mixer V-6 and
Second Heterodyne Oscillator V-8 are substituted for
the Gate tube V-7.
Input Coupling - The antenna coupling is designed
to
provide optimum coupling from a 95 ohm trans-
mission line. Abalanced doublet or straigHt wire
antenna may be used.
RF Amplifier - An ingeniously designed rotary
turret is employed to change bands and to place the
coil assemblies of the RF amplifier V-I and V-2, Mixer
V-5 and First Heterodyne Oscillator V-4 stages di-
rectly adjacent to their respective sections of the four
gang tuning capacitor and their respective tubes. This
assures maximum sensitivity at high signal to noise
ratio.
First
Heterodyne Oscillator - (Variable V-4)-
The rotary turret band change switch, advanced de-
sign of the four gang, twin section, variable tuning
capacitor and rugged construction throughout, pro-
vide frequency stability and dial calibration accuracy
to apreviously un attained degree.
First
Heterodyne Oscillator - (Crystal Controlled
V-3) - For services requiring extremely stable, fixed
frequency operation, acrystal controlled high fre-
quency oscillator is provided. Instant changeover from
variable to crystal controlled oscillator with achoice
of six crystal positions, is effected by a front panel
control. Asecond front panel control permits adjust-
mentof the crystal oscillator frequency over a plus
or minus .005 percent range.
Intermediate Frequency Amplifier -Single conver-
sion to 455 kc is employed for signal frequencies below
7.4 mc. There are four stages of IF amplification
incorporating the Hammarlund patented crystal filter
circuit. Six positions
of selectivity provide 6 db band-
widths of .2, .5, 1.3, 3, 8, and 13 kc. On the three
narrower bandwidth positions, the crystal filter is in
operation. The crystal phasing control provides ex-
treme selectivity for the high attenuation of closely
adjacent interfering signals.
Double conversion is employed for signal frequen-
cies above 7.4 mc. The signal is heterodyned to 3.955
mc
by the First Mixer V-5 and Heterodyne Oscillator
V-4 or V-3 for high image rejection. The 3.955 mc
signal is
then heterodyned to 455 kc by the Second
Mixer V-6 and the 3.5 mc Fixed Crystal Controlled
Oscillator V-8, for selectivity.
Detector and A VC - The V- 14 tube is used as a
high level Detector and AVe Rectifier. The ·AVC
circuit is provided with separate time constants
fGlr CW and MCW operation. Ave and Diode
output terminals provide for connections in diversity
applications.
Beat
Frequency Oscillator - The beat frequency
oscillator employs a high capacity Colpitts circuit
which gives a high order of frequency stability and
minimizes oscillator harmonics. The beat frequency
Oscillator V-l3, is coupled into the detector circuit
through Buffer Amplifier V-12, which eliminates oscil-
lator lock-in and permits variation of the beat oscillator
injection
by means of acontrol located on the rear of
the chassis. A front Panel control varies the audio
beat frequency, from zero beat to plus or minus 3kc.
Noise Limiter -
The noise limiter circuit V-IS,
limits the noise interference from ignition systems or
other sources of pulse type noise. A separate control
switch S-6, permits optional use of the limiter on any
mode of operation when pulse type interference is
present.
Audio Frequency Amplifier - A resistance coupled
amplifier
triode V- 16-B, amplifies the audio frequency
signal from the detector.
Audio Output - The audio output tube V- 17, is
transformer coupled through asplit, balanced winding
to deliver 2.0 watts undistorted output to a600 ohm
load. The split balanced winding permits balancing
of the direct current in the output circuit, as used for
teletype or similar service. A separate secondary wind-
ing provides attenuated audio signal output for head-
phone operation. This winding will deliver an output
of 15 milliwatts into an 8000 ohm resistive load when
the 600 ohm power secondary is delivering 500 milli-
watts to a600 ohm resistive load.
IF Output - A cathode follower V- 16-Aprovides
a70
ohm impedance source of intermediate frequency
(455 kc) to socket, SO-239, on the rear skirt of the
chassis. APL-259 plug and RG- 11/U cable, not sup-
plied, are used for this connection.
Power Supply - The power supply is ali integral
part of the receiver. It includes the Brectifier V- 19
and the erectifier V-20, together with their respective
low pass filters
and the Voltage Regulator V-18. The
power transformer is provided with screw terminal
primary taps, covering a power line source range of
90 to 270 volts, 50 to 60 cycles. The power trans-
former and filter components are protected by fuses
in
the primary and plate supply circuits.
[6 ]

Tuning Meter - The tuning meter is used on A VC
operation to indicate the accuracy of tuning and the
relative strength of received signals. Depression of
the Meter Switch converts the meter circuit for indica-
tion of output level in db from 6milliwatts.
RF Gain Control and Power Switch - The RF gain
control' is provided for manual control of sensitivity
to prevent overloading on strong signals when op-
erating with the A VC-MANUAL switch in the
"MANU AL" position. This control also operates
when the switch is in the "A VC" position. The
Power "ON -OFF" switch is operated at the counter-
clockwise extremity of the RF gain control.
3.5mc
CRYSTAL CONTROLLED
Send-Receive Switch - The send-receive switch de-
sensitizes
the receiver but leaves the power "on" to
provide for instant reception between transmission
periods.
Convenience
Outlet - A convenience power outlet
is provided on the rear of the chassis for the connec-
tion of an accessory such as alamp or electric clock.
Radiation -
Advanced design and shielding of the
high frequency, second conversion crystal and beat
frequency oscillators has reduced radiation to a
negligible
point so that interference of this nature,
common in multi-receiver installations, is reduced to
aminimum.
V1
RF
6BA6
V4
VFO
6G4
V2
RF
6BA6
V3
FFO
6AG7
CRYSTAL CONTROLLED
IF OUTPUT
V14B
AVG
6AL5
V14A
DET
6AL5
TO OUTPUT
LEVEL METER
• BLOCK DIAGRAM·
--- Signal path cammon to all frequencies
•••••••••••• Signal path tor frequencies above 7.4 mc
----- II " U below 7.4 me
FIG. 2
III
INSTALLATION
Tubes and Packing - After unpacking the receiver
see
that all tubes are firmly in their sockets and that
any packing material is removed from the receiver.
Power Supply - Make sure that the primary tap
lead at the bottom of the power transformer is con-
nected to the tap which most nearly agrees with the
50 to 60 cycle power source voltage.
Antenna - The input impedance at the antenna
socket, UG-I03/U, is designed to match a95 ohm
transmission line. The angle plug adapter, UG- 104/U,
and connector plug, UG-102/U, supplied with the re-
ceiver, are for use with RG-22/U cable which should
be used with abalanced antenna installation. If it is
desired
to operate with asingle wire antenna, the
antenna lead-in wire should be connected to one
terminal of the connector plug and a ground lead
should
be connected from the other terminal of the
[ 7 ]
connector plug to the ground terminal, which is
adjacent to the antenna socket at the rear of the tun-
ing unit.
Speaker - The speaker should be of the permanent
magnet dynamic type and should include aspeaker
voice coil
to 600 ohm line matching transformer for
connection to the 600 ohm audio output terminals of
the receiver. Caution: When the 600 ohm output is
not used, connect a600 ohm, 2 watt resistor to these
terminals
to avoid component damage from high
transient peak voltages. For applications requiring the
insertion of direct current control or indicating
voltages,
the jumper connecting the two balanced
sections
of the 600 ohm output may be removed and
the insertion circuit, such as alow resistance balancing
potentiometer, connected
in its place.
Headphones - Either high or low impedance head-

phones may be used by plug connection to the phone
jack, located at the lower left side of the front panel.
The high impedance type is recommended.
Mounting ~ The receiver is designed for either
table or rack mounting. Table models are supplied
in awell ventilated steel cabinet
with handles and
protective' rubber feet. Rack models, with top and
bottom cover plates are supplied for mounting in a
standard 19 inch rack. The panel is 10Yl inches high.
See Section
VII. The receiver should be placed in a
position
which permits the free access of air.
Crystals for Frequency
Control- Crystals, Y1 to
Y6, are not supplied with the receiver, but will be
supplied
on special order for any signal frequency
in the range of the receiver above .75 megacycle. In
order to insure correct crystal controlled frequency
operation, orystal units may
be ordered from HAM-
MARLUND MFG. CO. INC. and the order should
specify
the signal frequency, for which each unit is to
be used. See note at end of Table 5. To install crystals,
loosen
the knurled thumb screw on top of the Fre-
quency Control Unit, T34, and push the retainer
spring assembly
to the rear. Insert the crystal or
crystals in the sockets, numbered 1 to 6. Bring the
retainer spring assembly forward so that the springs
press on
top of the crystal holders and tighten the
thumb screw. Mark the signal frequency for which
each crystal was selected, in megacycles on the plastic
chart provided for this purpose alongside the crystal
switch, S2. Pencil
or ink 'may be used and can be
erased if it is desired to change these figures at any
time. The numerals on the chart should be used so
that they agree with the numerals on the crystal socket
positions,
which are also indicated by the crystal
selector switch.
Relay Connections -
If external relay operation for
the send-receive function is desired, connection may
be made by soldering a twin conductor cable to the
terminals of the Send-Receive switch, S9. In this case
S9 is left
in the Send or open position.
A
VC and Diode Output - Shunt connection to the
A VC bus and series connection to the detector diode
load are provided
at the rear of the receiver for di-
versity applications. The. Diode Output terminals
are provided
with awire jumper connection when
these terminals are not used for external connection.
IF Output - The IF Output socket, SO-239, at the
rear of the chassis provides fqr connection in diversity,
teletype
or other applications where asource of 455
kc, intermediate frequency
is required. APL-259 plug
and RG- 11/U cable should be used. This will provide
an output of approximately 200 millivolts to a,70 ohm
resistive load, with anormal sensitivity input of 2
microvolts signal.
Convenience
Outlet - The power outlet receptacle
at the rear of the chassis may be used for operating
an accessory, such as an electric clock or lamp.
IV
OPERATION
General- Before attempting operation of the
SP-600 receiver, the operator should thoroughly
familiarize himself with the functions and uses of the
various controls. When referring to the controls in
this description, the words in capital letters represent
the part ot the name adjacent to the control on the
front panel or on the rear skirt of the chassis. For
example, when referring to the SELECTIVITY con-
trol, the word SELECTIVITY in capitals indicates the
legend appearing adjacent to the control. Reference
to photographs, Figs. 1
and 6, is suggested while read-
ing this description. Front panel controls and dials
are
shown in Fig. 1and rear controls and terminals
are
shown in Fig. 6.
Selectivity Control - The SELECTIVITY control
is a6-position switch
which selects three crystal and
three non-crystal degrees of selectivity, ranging from
extremely
sharp for cw reception to broad for good
fidelity mcw operation.
The SELECTIVITY control
dial indicates
the 6 db bandwidth at each setting.
Phasing Control- The CRYSTAL PHASING
control is adifferential type, variable air capacitor.
It permits adjustment of the crystal selectivity char-
acteristic for high attenuation of closely adjacent
channel interference
on either side 6f the signal
frequency.
RF Gain Control- The RF GAIN control varies
the overall gain of the receiver. This control is opera-
tive in either position of the A VC- MAN switch.
Power Switch - The power; or on-off switch is
combined with the RF GAIN control. Complete
counter-clockwise rotation
of the RF GAIN control
throws the power switch to the off position, as indi-
cated
on the RF GAIN control dial.
Audio Gain Control- The AUDIO GAIN control
varies
the input voltage to the audio amplifier. This
control is also operative in either position of the A VC-
MAN switch.
Phones Jack - The PHONES jack is asingle circuit
jack operating
with the sleeve grounded and is suitable
to receive
any standard single circuit phone plug. It
is in the circuit at all times and is connected to a
separate secondary
winding of the audio output trans-
former,
which provides an attenuated signal for head-
phones. See Section
III installation.
Audio Output - The AUDIO OUTPUT is avail-
able at the four screw terminal board at the rear of the
chassis for connection to a600 ohm load. See Section
III installation.
Noise Limiter -
The LIMITER control switches
the noise peak limiter in or out of the circuit. This
control is operative independently of any position of
any other control. See Section 'II Circuit Description.
[ 8 ]

A VC-Manual Switch - In the A VC posltlOn the
AVC-MAN switch applies automatic bias potential,
to the controlled RF and IF amplifier tubes, there!>y
holding the audio output relatively constant over a
wide variation in
the strength of received signals. This
minimizes the variation of output due to fading of the
received signal and prevents blasting and overloading
when tuning through signals of greatly different
strength while traversing afrequency band. In the
A VC position the RF Meter circuit is operative for
indication
of tuning resonance and relative strength of
received signals. The RF GAIN control is operative
on A VC operation, when necessary to control excep-
tionally strong signals or to reduce noise, but the RF
meter is less effective when the RF GAIN control is
below maximum setting. In the MAN position the
A VC potential is removed from the controlled tubes
and the gain of the receiver is manually controlled
by the RF GAIN control.
CW-Modulation Switch - The CW-MOD control
in the CW position energizes the beat frequency oscil-
lator and connects an additional timing capacitor to
the A VC circuit to accommodate the A VC to slow
keying.
In the MOD position the beat frequency oscil-
lator is inoperative and the conditions are established
for either voice modulated or tone modulated signal
reception.
Beat Frequency Oscillator -
The BEAT OSC con-
trol varies the tuning of the 455 kc beat frequency
oscillator
over a range from zero beat to plus or minus
3kilocycles.
BFO Injection - The BFO IN] control adjusts the
cathode self bias of the beat frequency buffer ampli-
fier, thereby determining the injection voltage to the
detector tube.
Send-Receive -
The SEND-REC control is asingle
pole, single
throw toggle switch. In the SEND posi-
tion it desensitizes the RF amplifier, gate, second mixer
and 3.5 mc oscillator tubes during transmission periods.
Tuning Control and Dials - The TUNING control
rotates
the main tuning capacitor as well as the main
and vernier tuning dials. The main dial has six fre-
quency band scales, calibrated in megacycles, and an
arbitrary outer scale. The vernier dial has an arbitrary
a to 100 scale. The numeral under the upper or fixed
pointer of the main dial indicates the number of com-
plete revolutions that have been made by the vernier
dial
at any setting. Thus, if the pointer for the outer
scale of the main dial indicates over the figure 4 and
the vernier dial indicates 87.6, the reading to log for
this setting is read, 487.6. This precise mechanical
vernier system divides the rotation of the main dial
over each frequency
band into approximately 600
vernier divisions,
with one-half division calibration
points. Since it
is easy to estimate one-tenth divisions
on the vernier scale, this divides each frequency band
into approximately 6000 readable settings. This per-
mits extreme accuracy in the logging and resetting
of stations.
Tuning Lock - The TUNING LOCK, located to
the right of the TUNING control, provides apositive
[9 ]
lock for the tuning mechanism without affecting the
frequency setting when it is desired to prevent acci-
dental shifting of the tuning.
Band Change-Each revolution of the BAND
CHANGE .control turns the turret, containing the
RF and HF Oscillator coil, trimmer and switch contact
assemblies, from
one frequency band to the next. The
turret has no stops and may be turned in either direc-
tion desired. Apositive detent mechanism assures
correct location
of the various bands. The BAND
CHANGE control simultaneously operates the small
MEGACYCLES band indicating dial, located at the
center of the panel and aligns the dial frequency indi-
cator with the proper scale of the main dial.
Crystal Controlled
HF Oscillator - The XT ALS
control selects either variable high frequency oscillator
operation
or anyone of the six crystal positions, for
which similarly numbered crystal sockets are provided
in the Crystal Control Unit. See Section III Installa-
tion. The DELTA FREQ control compensates for the
small frequency tolerance to which the crystals are
made.
Meter Switch - The METER switch is adouble
pole, double
throw toggle switch with spring return
to the RF position. See Section II Circuit Description,
Tuning Meter.
Tuning Meter Controls- The METER AD] RF
control is used to adjust the resistance shunting the
meter when the METER switch is in the normal, or
RF position. It is adjusted to produce areading of
plus 20 db on the RF scale of the meter, with a10
microvolt
RF input signal and with the AVC-MAN
switch in the A Vp position. Depression of the
METER switch to the AF position converts the meter
circuit for indication of the AF power output level in
db from 6milliwatts. This switch is spring return to
the RF position when released and should not be de-
pressed
for the AF scale unless the audio output has
been adjusted for low power output, by means of
headphones or speaker. Failure to observe this precau-
tion
may result in damage to the meter. The METER
AD] AF control is used to regulate the meter current
when operating on the AF scale. This control is
adjusted to
obtain aa db reading on the AF scale of
the meter and is made with the audio power output
from the 600 ohm AUDIO OUTPUT terminals ad-
justed to 6milliwatts, or 1.9 volts across a600 ohm
resistive load.
Preliminary to
Operation - Turn the power switch
"on" by turning the RF GAIN control clockwise and
a.dvance this control to 10. Note that the dial lamps
hght. Place
the SEND-REC switch on REC and turn
the BAND CHANGE control to the frequency band
in which it is desired to operate. This should be done
at least 15 minutes before using the receiver, in order
to permit the tubes to warm up. Insert the headphones
plug
in the PHONES jack or use speaker as desired.
See Installation, Section III.
MCW Reception - Turn the TUNING LOCK to
its extreme counter-clockwise position and turn the
SELECTIVITY switch to 3kc. Put the CW-MOD

switch on MOD, the LIMITER switch to OFF, the
AVC-MAN switch on AVC, the XTAL PHASING
control at its center position and turn the XT ALS
switch to VFO. With the BAND CHANGE control
in
the proper position for the frequency band desired,
as indicated
by the MEGACYCLES dial, advance the
AUDIO GAIN control until some noise is heard. Turn
the TUNING control to indicate the desired fre-
quency on the main dial and tune the signal for maxi-
mum response or indication on the RF Meter. At
,resonance the main dial reading should be within one-
quarter of one percent of the signal frequency. Read-
just the AUDIO GAIN control for the desired output
level and as required to prevent overloading. Care-
fully tighten the TUNING LOCK by turning clock-
wise, if desired. The SELECTIVITY switch may be
turned to the 8kc or 13 kc position for improved high
frequency response if the signal to noise ratio is suffi-
ciently high. If the noise level is high, the SELEC-
TIVITY switch should be turned to the bandwidth
which provides the most intelligible reception and the
LIMITER switch should be thrown "on." If the
SELECTIVITY switch is used on either of the XT AL
positions, the XT AL PHASING control may be ad-
justed to either side of its center position to attenuate
an adjacent interfering signal. The RF GAIN control
may be
turned down somewhat to reduce noise, during
stand-by periods in the transmission, when traversing
the tuning range, or during deep fades of the signal.
The RF Meter scale calibration is for maximum RF
GAIN control operation and indicates only when the
A VC- MAN switch is on A VC. When searching for
very weak signals
the CW-MOD switch may be
thrown to CW and the BEAT OSC control set at O.
Locate and tune the signal to obtain zero beat and
then throw the CW-MOD switch back to MOD.
The Crystal Frequency Control may be used for
fixed frequency operation
at any signal frequency for
which crystals have been provided. See Section III,
Installation. Turn the XT ALS switch to the numeral
corresponding to
that on the panel chart for the de-
sired signal frequency. Set the main tuning dial to the
signal frequency and adjust the DELTA Ccontrol to
obtain zero beat with the CW,MOD switch on CW
and the BEAT OSC control at O. Throw the CW-
MOD switch to MOD and adjust the TUNING Con-
trol for maximum RF Meter indication or for maxi-
mum response.
CW Reception - The preliminary procedure for
CW reception is the same as for MCW reception
above. Place
the CW-MOD switch on CW and with
the BEAT OSC control at 0, tune the desired signal
for zero beat.
Adjust the BEAT OSC control, in
either direction, to obtain the audio pitch desired. The
AVC-MAN switch may be used in the position which
gives the best reception. Adjust the desired output
level by the AUDIO GAIN control when on A VC
and by the'RF GAIN control when on MAN. The
RF Meter does not operate on the MAN position. The
SELECTIVITY switch may be used in the XTAL
positions, as found desirable, to reduce noise or to
provide rejection
of an interfering signal. The XT AL
PHASING control is adjusted for minimum interfer-
ence from an adjacent, interfering signal.
If interfer-
ence
of this kind persists, further discrimination be-
tween the desired and the undesired signals may be
realized by slightly detuning the desired signal to the
opposite side of resonance from that on which the
undesired signal is located and readjusting the XTAL
PHASING control and the BEAT OSC control for
the desired signal. The Crystal Frequency Control
may be used as described under MCW Reception
above.
If reception is to be suspended and resumed at
short time intervals, the power should be left "on"
and for such operation the SEND- REC switch should
be
thrown to SEND between reception periods. This
keeps the receiver warm and ready for instant use.
When operation of the receiver is completed, turn
the power "off" by extreme counter-clockwise rotation
of the RF GAIN control.
V
MAINTENANCE
General- This receiver is designed for continuous
duty and should normally require little attention be-
yond the replacement of tubes. An occasional cleaning
of the gear teeth in the gear train is recommended to
prevent a heavy accumulation of dust which may
cause calibration
error and improper operation of the
gears. This may be done with asmall stiff bristle
brush,
turning the controls to obtain access to the
different portions of the gears. No grease or oil should
be used on the gears. Operation and maintenance of
the receiver will be greatly facilitated if the contents
of this instruction book are thoroughly digested.
Some sectionalizing
of faults is possible, if the fault
is not existant on all of the frequency bands. Non-
operation of the three lower frequency bands, with
normal operation on the three higher frequency bands,
indicates
that the fault is associated with the circuits
of tube V7. If only the three higher frequency bands
are affected, the fault is associated with the circuits
of V6 or V8. If only one single band is affected, refer
to HF Oscillator and RF Coil Assemblies in this
section.
Visual evidence
of trouble is usually a burned or
darkened resistor, which if found is likely caused by
excessive current due to a short circuited capacitor or
tube element at the load side of the resistor. In such
acase,
both the capacitor or tube and the resistor
should
be replaced as indicated. Refer to Figures 10
to 16 and Table 5for location and values of com-
ponents. If the checks on tubes, fuses and visual
inspection fail to disclose
the fault, the tube socket
voltages
and resistances should be measured and
checked against the values given in Tables 1 and 2.
Any appreciable departure beyond anormal variation
[ 10]

of approximately 15 percent from the values in these
tables will generally indicate
the component or circuit
at fault.
If the foregoing does not reveal the fault,
then astage by stage check of amplification should be
made as shown in Table 4. Any great difference from
the values of input shown in the table will indicate the
stage at fault. If a tuned circuit component, such as an
IF transformer, RF or HF oscillator coil assembly, is
found defective and replaced only the replaced unit
need be realigned. Follow the alignment procedure in
Section VI, for the unit involved.
The IF Transformers, Crystal Filter, Beat Frequency
Oscillator and the 3.5 mc Crystal Controlled Oscillator
assemblies
are each mounted on the chassis indepen'
dently of their respective shields. The shield can as'
semblies are easily removed for inspection of these
units, without disturbing the soldered connections. In
replacing these shields, make sure that the grounding
springs are in place on the inductance adjuster screws
before the shield is installed.
Vacuum Tubes - Weak or defective vacuum tubes
are the most common cause of decrease in sensitivity,
faulty
performance or failure of operation in are'
ceiver. In case of such faults, first rel)J.ove the tubes
and check them in a tube tester of reliable design. If a
tube tester is not available, substitution of a new tube
for each tube type and position should be tried. See
Figures 2
and 3. Such substitution is best made, one
tube at atime in order that the faulty tube may be
detected by the improvement or restoration of per'
formance by the new tube.
Locating Faults - If the dial lamps do not light
when the power switch is turned on, check for ablown
line fuse,
Fl and replace it at the rear of the receiver
from the spare fuses. An open circuit in the line cord
or plug may be checked by plugging alamp first in
the power source receptacle and then in the ac re'
ceptacle on the rear of the receiver. If the dial lamps
light but there is no sound at all in the headphones
or speaker, check for a blown minus Bfuse, F2 and if
blown, replace it with aspare fuse. In replacing fuses,
make sure that only a3ampere fuse is inserted in the
line fuse holder and that only a%ampere fuse is
inserted
in the minus Bfuse holder. Should neither
fuse be blown, nor replacement of the fuses restore
operation,
the receiver should be removed from its
cabinet
or rack and inspected for visual signs of
trouble. The table model receiver is held in the cabinet
by two screws through the cabinet bottom and by the
four screws through the slotted holes at each side of
the front panel. The rack model receiver is provided
with bottom and top cover plates which should be
removed for purposes of inspection and repair.
IF Transformers - If afault is traced to one of the
variable coupled IF Transformers, T4 or T5, check
whether the fault exists on all positions of the selec,
tivity switch S5,
or only on one position of this switch.
If the faulty operation occurs on only one switch
position, check
for continuity of the coupling coil
associated
with that position, check for imperfect
soldered connections
at the coil and switch terminals
and check the switch contact involved. If faulty opera'
tion localized at one transformer exists on all positions
[ 11 ]
of the selectivity switch, make the continuity check on
the plate. coils, on the main grid coil and on the wiring
associated with these coils. Transformers 1'4 and T5
and Crystal Filter T3 have additional inner shield
assemblies
that are held in place by the tension nuts
on the adjusting screws. To remove these shields, hold
the adjusting screws with ascrew driver to prevent
turning the screws and losing the alignment adjust,
ment and loosen the tension nuts, using another small
screw
driver engaging one of the slots. When replac'
ing these shields and tension nuts, employ the same
method and tighten the tension nuts just enough to
prevent the adjusting screws from working loose.
Beat Frequency Oscillator - To remove the beat
frequency oscillator T6, if the receiver is equipped
with the Crystal Frequency Control Unit T34, it will
be necessary to set the crystal selector switch S2, on
its number 3position and loosen the four set screws
in the rigid shaft coupling and the two set screws in
the disc on the selector switch shaft. Slide the switch
shaft forward through the coupling and disc. It may be
necessary
to remove burrs, caused by the set screws,
from
the switch shaft in order to slide the shaft
through the disc. Now loosen the four set screws of
the flexible coupling on the BFO shafts and slide the
coupling forward on the BFO drive shaft in the front
panel. Remove the BFO shaft bearing bracket by
taking out the two screws holding it to the chassis.
Unsolder the leads from the six terminals of the BFO
unit at the underside of the chassis, being careful to
not overheat the wire of the shielded cable since this
wire is insulated with polystyrene and is easily dam-
aged by heat. Note that if this cable wire is grounded
to its shield, there will be no beat frequency voltage
input to the buffer tube V12 even though the beat
oscillator is functioning properly. Therefore, with the
shielded lead disconnected from the lug of the BFO
unit, check with a continuity or ohmeter the connec'
tion of this wire to the buffer tube V12 and its freedom
from
the chassis. Carefully observe the wiring of the
BFO unit for correct replacement. See T6 on Figure
14.
Now remove the two screws holding the BFO
shield can to the chassis and the two screws at the
underside of the chassis and remove the BFO unit.
When replacing the unit, follow the reverse procedure.
Before
tightening the two screws holding the unit
to the chassis and the two screws holding the shaft
bearing bracket, adjust the unit and shaft bracket to
obtain alignment of the two shafts at the coupling.
Make sure that the shield grounding spring is in place,
with the bow of the spring downward against the
tension nut, before replacing the shield can assembly.
Adjustment of BFO - With the AVC,MAN
switch on A VC, and the SELECTIVITY control on
the .2 kc position, tune in an unmodulated signal for
maximum tuning meter reading. Set the CW,MOD
switch to CW and with the BEAT OSC dial at 0,
adjust the top screw of the BFO unit for zero beat.
Turn the BEAT OSC dial to each 3kc position and
check the output beat frequency against a known
audio frequency source such as agood audio oscillator.
If the beat frequencies obtained at each 3kc position
is
not within the range between 3 and 3.5 kc, loosen
the set screws of the BFO shaft coupling and turn the

shaft of the BFO with respect to the drive shaft and
repeat the above, resetting the 0 adjustment by the top
screw of the BFO unit each time until the above range
is realized. One set screw should be used just tightly
enough to allow the drive shaft to operate the BFO
shaft until the range is correct and then tighten both
screws.
Crystal
Switch Adjustment - If the mechanical
drive
of the crystal control switch has been disturbed,
it should be adjusted as follows: Carefully slide the
switch shaft through the disc and into the rigid
coupling
and being careful not to turn the switch,
tighten the four set screws in the rigid coupling, with
the knob indicator on the number 3position as
originally set
under Beat Frequency Oscillator. Now
set the crystal switch on the number 1position and
holding the disc in acounter-clockwise direction, so
that the end of the slot in the disc is against the drive
pin, lightly fasten the set screws of the disc. When
this disc is properly adjusted on the shaft, with the
switch in the number 1position, the connecting bar
between the two discs should not be under tension and
should exhibit aslight amount of play when tried
with the thumb and forefinger. When so adjusted,
tighten the set screws.
Crystal
Control Unit - If it has been determined
that the Crystal Control Unit is defective, it will be
necessary to remove
the unit for repair or replacement.
Refer to Figures 15 and 16 and unsolder the lead of
capacitor C60 from switch S3 on the gear plate. Un-
solder the black, black-white, blue-red and red-white
leads of the crystal control unit from terminal strip
E13
underneath the chassis and unsolder the red lead
of the unit from filter capacitor C161. Remove the
XT ALS switch shaft, as described under Beat Fre-
quency Oscillator. Loosen set screws and remove the
delta Ccontrol knob. Remove the nut and lockwasher
at the top of the bracket post adjacent to the power
transformer and remove the bracket over the filter
chokes.
The front end of this bracket is slotted and
engages agroove in a mounting post of the crystal
control unit.
Remove the four screws that secure the
filter assembly panel to the mounting posts at each
corner of this panel and move the filter assembly suffi-
ciently to permit removal of the four screws holding
the crystal control unit to the chassis. When these
screws are removed,
the unit may be taken from the
receiver. In removing the unit and in subsequently
handling it, be careful to avoid any strain on the delta
Cshaft,
or the delta Ccapacitor may be damaged. Re-
move the four screws holding each of three sides of
the cover and spring the two top ends of the cover
enough to make the flanges clear the top of the box.
Hold these flanges apart to prevent their edges from
damaging the rf chokes in the unit while sliding the
cover off the crystal unit box. When the unit is to be
replaced, follow
the reverse of the above procedure.
Follow
the procedure under Crystal Switch Adjust.
ment to properly rein.~tall the switch mechanism.
HF Oscillator and RF Coil Assemblies - If faulty
operation occurs in only one frequency
band of the
receiver, the trouble should be found in one of the
four coil assemblies for that band in the tuning unit
turret. For example: Coil assemblies T13, 19, 25 and
31 should be examined if band 7.4 to 14.8 mc only,
does
not perform normally. To remove these coil
assemblies
stand the receiver on its right or left side
and remove the bottom cover plate from the tuning
unit. Turn the band change control to place the band in
question in its normal
operating position and then turn
the band change control two and one-half revolutions
counter-clockwise.
This will place the band coil as-
semblies parallel and at the bottom of the tuning unit.
Now remove the two springs holding one coil assembly
in the turret and carefully remove it by sliding it
towards you and off the tongues of the shields. It is
best
to remove only one coil assembly at atime and
inspect it for defects or substitute areplacement as-
sembly if available. Caution: Make sure that the coil
base is firmly seated
and secured by its retaining springs
before going
to the next assembly or turning the band
change control. Failure to do this may damage the
switch spring contacts beyond repair. Repeat this pro-
cedure until the faulty assembly is found. In checking
these assemblies, first check
for continyity of the coils,
particularly
the small primary coils as in the RF Input
assemblies, where they are liable to damage if the
receiver is operated in the presence of very strong
transmitter signals. In replacing these coil assemblies
be careful
that the end of the assembly nearest the
coil is toward the front of the receiver.
Mixer Plate Coil Assembly - Trouble in the Mixer
Plate Coil Assembly Tl, is indicated if the input re-
quired at pin 7 of V5 is found to be greatly different
than the values shown in Table 4, and the gain from
pin 7 of V6 is normal. To obtain access to the com-
ponents of the mixer plate coil assemblies it is neces-
sary to remove the crystal control unit and the filter
assembly as described
under Crystal Control Unit. The
cover plate and shield of Tl may then be removed for
replacement
of adefective component. If the entire
assembly is to be replaced,
it will be necessary to un-
solder all of the leads at both the bottom and top
terminal boards of the unit. Refer to Figure 15 for
components and wiring of Tl.
RF Tube Platform - If the receiver fails to per-
form normally on any of the six frequency bands and
the previous tests indicate that performance of the IF
and audio frequency amplifiers is normal, including the
gain check in accordance with Table 4for the irwut to
pin 7 of V5, the fault is indicated to be in the RF Tube
Platform or in the main tuning capacitor. Before re-
moving the RF Tube Platform, it is advisable to re-
move the top shield cover and inspect the main tuning
capacitor connections. Refer to Figures 8 and 15.
Observe that the tuning capacitor is operating prop-
erly when the tuning control is rotated. Using aminia-
ture tube adapter, see Section VI alignment, apply a
modulated
rf test signal successively to pin 1 of VI
and V2 and to pin 7 of V5. For each of these positions
of the adapter and signal, tune through the proper dial
setting
for the signal frequency used. Gain of the
order of 5 or 6should be indicated for each stage and
loss of signal will indicate the section to be investi-
gated for the fault. No signal output, when the input
signal is applied to pin 7 of V5, will indicate trouble
in
the HF oscillator section of the unit. With the
[ 12 ]

covers removed from the tuning capacitor and Tl,
refer to Figure 15 and unsolder the blue, white-black,
red-white, red-green, yellow-black
and blue-red leads
that come from the tube platform at the top of Tl.
Unsolder the leads from the tuning capacitor rotors,
stators
and ground straps at each section. Unsolder
the lead from the tube platform at 83. Turn the Band
Change control one-half turn from any band position
in order to have the band switch contacts disengaged
and leave the band switch in this position until the RF
tube platform is replaced, otherwise irreparable dam-
age to the switch contacts will occur. Remove the four
screws at the corners of the top of the platform and the
four screws at the side flange and carefully remove the
platform. In handling be careful to prevent damage to
the switch contacts of this assembly. When the unit is
ready to be replaced, follow the reverse of the above
procedure. '
[ 13 ]
Main Tuning Capacitor- If it is necessary to re-
place the main tuning capacitor, the proc.edure is as
follows:
Remove the top cover and unsolder the leads
of the capacitor as described under RF tube Platform.
Bring the c'!-pacitor to full mesh by means of the tuning
control. Carefully remove the spring and drive link
at the front of the capacitor. Remove the single screw
that secures the capacitor frame front plate to the
gear plate, looping apiece of small wire around the
spacing washer between the capacitor and gear plate.
The front capacitor plate is located and held in posi-
tion by two dowel pins and will not move when the
front screw is taken out. Now hold the capacitor by
its frame with one hand and remove the rear support-
ing screw and spacer. The capacitor may now be
moved
to the rear, to disengage the dowel pins, and
lifted from the receiver. Follow the above procedure
in reverse when replacing the capacitor.

TUBE SOCKET VOLTAGES-TABLE 1
Voltage to chassis. Measurements made with Weston Model 663 Volt-Ohmmeter, except those indicated by
asterisk were made with Measurements Corp. Model 62 VTVM. The 500 volt scale was used for all voltages
above 10 volts
and the 10 volt scale for voltages below 10 volts. Line voltage 117, no signal input. Audio Gain
control
at minimum and CW-MOD switch on HCW"
SOCKET
PIN NUMBERS
TUBE 12 3 4 5 67 8 9 MODE OF
OPERATION
V-I *-1
-*6.3ac -200 90 - - - RF Gain max.
V-I
*-54
-*6.3ac -260 235 - - - RF Gain min.
V-2 *-1
-*6.3ac. -210 100 - - - RF Gain max.
V-2 *-54
-*6.3ac -260 240 - - -
RF Gain min.
V-3 -*6.3ac -- - 0-265 -
RF Gain max.-VFO operation
V-3 -*6.3ac - - -150 -265 -
RF Gain max.-Crystal Freq. Control
V-3 -*6.3ac - - - 00290 -
RF Gain min.-VFO operation
V-3 -*6.3ac - - -150 0280 - RF Gain min.-Crystal Freq. Control
V-4
130 -*6.3ac -130 - - - - RF Gain max. or min.
V'5
-1.2 *6.3ac -140 110 ---
RF Gain max. or min.
V-6 --*6.3ac -225 -
*-1 - -
RF Gain max.-Freqs. below 7Amc
V-6 --*6.3ac -260 -
*-1 --RF Gain
min.-Freqs. below 7Amc
V-6 --*6.3ac -225 90
*-1
--
RF Gain max.-Freqs. above 7Amc
V-6 --*6.3ac -260 105 ':'-1 --RF Gain
min.-Freqs. above 7Amc
V-7 0-*6.3ac -215 125 304
--
RF Gain max.-Freqs. below 7Amc
V-7 0-*6.3ac -240 140 3.8 - -
RF Gain min.-Freqs. below 7Amc
V-7 0-*6.3ac -215 0 0 --
RF Gain max.-Freqs. above 7Amc
V-7 0-*6.3ac -240 00--
RF Gain min.-Freqs. above 7Amc
V,8
0-*6.3ac -0--- - Frequencies below
7Amc
V-8 30 -*6.3ac -30 ---Frequencies above
7Amc
V-9 *-1
-*6.3ac -205 90 --
--
RF Gain max.
V-9
*-54
-*6.3ac -260 235 ---
RFGain min.
V-I0
~'-1
-*6.3ac -205 90 - --
-
RF Gain max.
V-1O
*-54
-*6.3ac -260 235 - - -
Rf Gain min.
V'11
*-7.8
-*6.3ac -210 140 ---
RF Gain max.
V-11 *-7.8
-*6.3ac -235 140 - - -
RFGain min.
*6.3ac.
V-12 ---210 40 ---
RF Gain .max.-BFO Injection max.
V-12 --*6.3ac -240
45
--
-- RF Gain min.-BFO Injection max.
V-13
25
-*6.3ac -
25
----
RF Gain max. or min.
V-14 --*6.3ac -
"22
----
RF Gain max. or min.
V-15 --*6.3ac ---- - -
RF Gain max. or min.
V-16 50 -1.5 --210 -
604 *6.3ac
RF Gain max.
V-16 52 -1.6 --240 -
704 *6.3ac
RFGain min.
V-17 --260 228 --*6.3ac
12
- RF Gain max.
V-17 --280 265 --*6.3ac
13
- RFGain min.
V-18 150 ---150 ----
RF Gain max. or min.
V-19 -300 -----300 -RF Gain
max.-* 5 V ac Pin 2to Pin 8
V-19 -320 -----320 -
RF Gain min.-*5 Vac Pin 2 to Pin 8
V-20 -
*-96
*6.3ac ---
*-96
--
RF Gain max.
V-20 -
*-97
*6.3ac ---
*-97
-- RF Gain min.
[14 ]

TUBE
SOCKET
TERMINAL RESISTANCE-
TABLE
2
Resistance to chassis.
Measurements made with Weston Model 663 Volt-Ohmmeter.
Tube removed from ,socket under measurement. Audio Gain Control at maximum, RF Gain Control at mini-
mum. Limiter Switch
"OFF".
CW-MOD Switch on '·CW". AVC-MAN Switch on "AVC".
Socket
Pin No. 245 6 789 MODE OF OPERATION
Tube
Socket
V-I
1.8M 0 0 48K
80K
0
V-2 1.8M 0 0 48K
80K 0
V-3 0 0 47K 046K 46K Crystal Freq. control pos.
1"-6
V-4 Inf. Inf. 0Inf. 47K 0Crystal Freq. control pos.
1-6
V-4 48K Inf. 0Inf. 47K 0
VFO Operation
V·5
47K 150 048K 53K
26K
Freq. Band 1.35·3A5mc
V·6
22K 00
46K Inf.
lOOK Freq. Bands below 7Arnc
V-6 22K 0 0
46K 70K
lOOK Freq. Bands above 7Arnc
V-7 380 00
46K InL 390 Freq. Bands above 7Arnc
V-7 380 0 0 46K
80K 390 Freq. Bands below 7Arnc
V-8 0
InL
22K 0Freq. Bands below 7Arnc
V·8
0150K 22K 0Freq. Bands above 7Arnc
V-9
l.3M 0052K 80K 0
V-lO
l.3M 0052K
80K 0
V·ll
95K
0048K 50K 0
V-12 0 0 048K 145K *
*0 to lK (BFO Injection control)
V-13 0195K lOOK
0
V·14 0 870K 016K 0.lOOK
V-IS
94K Inf. 0
InL
0220K
V·16
l50K 500K lK
0 0 46K 470K
680
V·17 0 0 46K 46K 470K
InL
360
V-18 118K 78K 0
V-19 46K 0
55 55
46K
V-20 50K 65K 050K 0
65K
[lS ]

VI
ALIGNMENT
The alignment of a modern communications re-
ceiver requires precision instruments and a thorough
knowledge of the circuits involved. This receiver, be-
mg adouble super-heterodyne, the alignment proce-
dure is even more involved than is usual.
Under normal service the receiver will stay in align-
ment for extremely long periods of time, consequently
realignment should
not be attempted unless all other
possible causes of aparticular trouble have been elim-
inated. When it has been determined that any realign-
ment should be attempted, a great deal of caution
should be exercised in making
the adjustments, as any
required readjustment should not entail more than a
slight angular motion
of the adjusting screw.
ALIGNMENT OF THE IF STAGES
The signal generator should be modulated 30 per-
cent at 400 cycles. Turn the selectivity switch to the
3kc position and advance the RF Gain control to
maxim-um.
Set the signal generator frequency to 455
kc
and adjust its output until some deflection is noted
on the output meter. Refer to figure 3 for the location
of the various alignment adjustments. Adjust L42,
lA1, L39, L38, L36 and L32 for maximum output, re-
ducing the signal generator output and the RF Gain
control as required to prevent overload or excessive
output,
Now turn the selectivitv switch to thJu).arrow-
The low frequency IF should be aligned first. The
recommended method for aligning the low frequency
IF involves the use of asweep frequency signal gen-
erator and an oscilloscope. Since these instruments are
not available
at the average service station the alter-
nate method using an amplitude modulated signal gen-
erator and an output meter will be described first.
The additional information required for the visual
alignment
method will be covered in a later paragraph.
The signal generator should be coupled to the grid
of the mixer tube Y5 through acapacitance of ap-
proximately .01 mfd. A miniature tube adapter will
be
required to make the mixer grid connection avail-
able. Asuitable adapter, A/N No. CY-49519, is
available as
Part No. 977 from Alden Manufacturing
Co., 117 N. Main Street, Brockton, Mass. An output
meter should be connected across the output terminals
of the receiver or the speaker voice coil. The receiver
controls
should now be set as follows:
Control
Selectivity
Send -Receive
CW-Mod
Phasing
AYC-Man
Audio Gain
RF Gain
Band Switch
Dial
Position
See text
Receive
Mod
Arrow
Man
Set for approx. 20 volts
See
text
1.35 -3.45 mc
2.5 mc
est position,
.2 kc, and adjust the signal generator fre-
quency for the maximum output. This establishes the
correct signal frequency by the 455 kc crystal for the
IF amplifier and the frequency of the signal generator
.should not be disturbed for the remainder of the low
frequency
IF alignment, unless it should be to ~echeck
this establishment of crystal frequency to make sure
that the signal generator frequency has not drifted
during the alignment. The selectivity switch is now
'turned to the 3kc position and L42, L4i, L39, 'L38,
L36 and L32 are again adjusted for maximum output.
Now turn the selectivity switch to the 1.3 kc pos;tion
and adjust L37 for maximum output. Before chang-
ing this set-up the BFO should be turned on by throw-
ing the CW-Mod switch to CW and checked for zero
beat with the BFO knob dial at its zero reading. If
necessary L44 should be adjusted for zero output. This
check and adjustment of the BFO should be done with
the signal generator carrier unmodulated.
The procedure for the visual method of aligning the
low frequency IF should be the same as the above ex-
cept that the adjustments are made for both maximum
amplitude
and coincidence of. the oscilloscope images.
The oscilloscope vertical input should be connected
acroSs the diode detector load resistance, from the
junction of R64 and R65 to chassis. .
The high frequency IF should be aligned next. Set
the band switch to the 7.4 -14.8 mc band. The se-
lectivity switch should be in the 3 kc position. Adjust
the signal generator frequency to 3.955 mc and adjust
L31,
LB and L34 for maximum output.
The 3.5 mc crystal used in the second conversion
oscillator circuit is held
to avery close frequency tol-
erance and may be used as afrequency standard at
multiples of 3.5 mc from 10.5 mc upwards. In order
to do this, in view of the complete shielding against
radiation
from this oscillator, it will be necessary to
temporarily connect a two foot length of insulated
wire
to the antenna terminal and dress the free end
of this lead around the tube shield on the 3.5 mc
oscillator
tube Y8. This test lead should, of course,
be removed except while in use as afrequency
standard.
[16 ]

ALIGNMENT OF THE RF 'AMPLIFIER & HF OSCILLATOR
To adequately align the RF Amplifier and HF Os-
cillator an accurately calibrated signal generator and
an output meter are required. The frequencies re-
quired are shown in table 3. The location of the ad-
justments is shown in Figure 3. The use of Table 3
and Figure 3should be made in following this part of
the alignment which will now be described for one
frequency band. The same procedure should then be
followed
for the other frequency bands.
To align the .54-1.35 mc band the signal generator
is coupled
to the antenna input terminal through a
100
ohm carbon resistor. The generator should be
modulated 30
percent at 400 cycles and the output
meter connected across the receiver output terminals.
The receiver controls should be set as follows:
Control
Selectivity
Send-Receive
CW-Mod
AVC-Man
Audio Gain
RF Gain
Band Switch
Limiter
Position
3kc
Receive
Mod
See Text
Set for approx. 20 volts
See
text
set for band to be aligned
off
Set the receiver and signal generator dials to .56 mc.
The RF Gain control should be set at maximum and
the A VC - Man switch set on A VC. The HF Osc. L
adjustment shown in Figure 3, should now be set for
maximum
output. Then the Ant., 1st RF and 2nd RF
Ladjustments should be set for maximum output. The
receiver and signal generator dials are now set to 1.3
me
and the Cadjustments, shown in Figure 3, should
be adjusted
for maximum output in the same order,
beginning
with the Osc C adjustment and then mak-
ing the C adjustments for the Ant, 1st RF and 2nd
RF. This procedure should be carefully repeated un-
til no increase in output can be realized. The A VC -
Man switch should then be set to Man and the signal
generator should be set for approximately 3micro
volts.
The Land C adjustments should now be
checked
for maximum output, adjusting the RF Gain
control as
found necessary to maintain the output at
approximately 20 volts.
Following
the frequencies, shown in Table 3, align
the remaining bands using the same procedure as
above.
TABLE No. 3
RF AND HF OSCILLATOR ALIGNMENT FREQUENCIES AND ADJUSTMENT DESIGN A nONS
FREQ. BAND
IN MC
.54-1.35 1.35-3.45 3.45-7.4 7.4-14.8 14.8-29.7
29.7-54.0
RF &' HF OSC
ADJUST LAT.
.56 1.4 3.75 7.5 15.0 30.0
RF &' HF OSC
ADJUST CAT. 1.3 3.4 7.15 14.5 29.0 52.0
TABLE No.4
APPROXIMATE SIGNAL INPUT AT. IF Be AF STAGES FOR 20 VOLTS OUTPUT
Output measured across a600 ohm resistive load at output terminals of receiver. RF signals modulated
30
percent at 400 cycles. Signals applied to tube g~ids through a .01 mfd capacitor. Select~vity switch at 3kc
AVC - MAN switch on MAN. CW - MOD SWItch on MOD, RF Gam and AudIO Gam at maXImum.
BAND SWITCH
FREQUENCY
INPUT TO APPROX. INPUT
Any
Audio 400 cycles
Pin5,V17 5.5 volts
Any
Audio 400 cycles
Pin 2, V16B
.5 volts
1.35-3.45 mc
Mod RF 455 kc
Pin 1, VII
.6 volts
1.35·-3.45 mc
Mod RF 455 kc
Pin 1, VI0
15000 microvolts
1.35-3.45 mc
Mod RF 455 kc
Pin 1, V9
300 microvolts
1.35-3.45 mc
Mod RF 455 kc
Pin 1, V7
75 microvolts
1.35-3.45 mc
Mod RF 455 kc
Pin 7, V5
90
microvolts
7.40-14.8 mc
Mod RF 3.955 mc
Pin 7, V5
70 microvolts
7.40-14.8 mc
Mod RF 3.955 mc
Pin 7, V6 180 microvolts
[ 17 ]