Hammarlund SP-600-JX-17 Parts list manual

DESCRiPTIO ....
AND
SP -600-JX17
COMMUNICATIONS
RECEIVER
FOR
SINGLE AND DIVERSITY
RECEPTION
",
"\~.
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...
:::.... TECHNICAL
-
-
-
I::
l - OPERATING
I IN&TIIIUCTIONS
L-.~ ~
Hammarlund Manufacturing Company
A Giannini Scientific Co.
73-88 HAMMARLUND DRIVE
MARS HILL, NORTH CAROLINA
9012-06-00002
ISSUE 2
REVISED 8~67

SP-600-JX17
COMMUNICATIONS RECEIVER
INSTRPCTION AND SERVICE MANUAL
INSTRUCTION AND SERVICE INFORMATION
ESTABLISHED 1910
In order to receive the full unconditional gO·day warranty against
defective material and workmanship in this receiver, the warranty ..
card must be filled out and mailed within two weeks of purchase.
Please refer to serial number of warranty in correspondence.
HAMMARLUND MANUFACTURING CO.
AGIANNINI SCIENTIFIC CO.
73-88 Hammarlund Drive, Mars Hill, N. C.

TABLE OF CONTENTS
SECTIONS
No. Title Page
I INTRODUCTION. .................................................... .. 1
II CIRCUIT DESCRIPTION. ............................................. .. 2
III INSTALLATION. .................................................... .. 4
IV OPERATION ........................................................ .. 6
V MAINTENANCE. .................................................... .. 9
VI ALIGNMENT. ....................................................... .. 12
VII REPLACEABLE PARTS LIST. ........................................ .. 25
ILLUSTRATIONS
Figure Title Page
1. Front Panel. ......................................................... .. 5
2. Block Diagram. ...................................................... .. 17
3. Top View of Chassis-Alignment Adjustments. ............................. .. 18
4. Audio
and Fidelity' Curves ............................................. .. 18
5. Selectivity Curves. ....................................................
.. 20
6.
Rear View of Chassis. ............................ .. ................... .. 21
7. Top View of Chassis .................................................. .. 22
8.
Parts Identification for Locating Test Points. ............................. .. 23
9.
Schematic Diagram '. .......................... .. 33
10. Connection Diagram-Receiver Chassis. ....................................
.. 35
11. Tuning Unit Connection Diagram. ....................................... .. 31
12.
Crystal Control Unit Connection Diagram. ................................ .. 32
TABLES
No. Title Page
1. Tube Socket Voltages. ................................................ .. 14
2. Tube Socket Terminal Resistance. ....................................... .. 16
3. RF and HF Oscillator Alignment Frequencies and Adjustment Designations. ... .. 19
4. Approximate Signal Input at IF & AF Stages for 20 Volts Output. .......... .. 19

SECTION I
INTRODUCTION
The SP-600-JX17 is a 20-tube superheterodyne
radio communications receiver designed specifically
for
diversity reception. The receiver is intended for
use as either the "master" or "slave" unit for the re-
ception of MCW, CW, suppressed carrier, or fre-
quency-shift signals.
"Master-slave" relationship is established by
interconnecting two or more receivers. These con-
nections may be made between the beat-frequency
and/or the heterodyne oscillators of each receiver,
or between the receivers and an externally connect-
ed master oscillator common to each.
Frequency drift, after a 15 minute warm-up,
ranges between .001 percent and .01 percent of fre-
quency,
depending on the frequency used. This is
an unusual degree of frequency stability for variable
tuned HF oscillators and closely approaches crystal
stability.
The frequency control unit provides for fixed
channel crystal-controlled operation on any six fre-
quencies
within the range from .75 to 54 megacycles.
Front panel controls permit the selection of either
the normal high stability, continuously variable tun-
ing or fixed frequency operation. For crystal-control-
led 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 control. Desired crystals may be pur-
chased on special order from the Hammarlund Man-
ufacturing Company.
The selectivity
control provides 3degrees of cry-
stal and 3degrees of non-crystal selectivity ranging
from sharp (.2 Kc) to broad (13.0 Kc). The crystal
filter in the SP-600-JX17 embodies the same circuit
features that have proved so effective and desirable
in Hammarlund Super-Pro receivers.
Two
stages of radio frequency amplification are
provided on all bands: single conversion is used for
signal frequencies up to 7.4 megacycles, and double
conversion, employing a
crystal-controlled oscil-
lator, for signal frequencies above 7.4 megacycles.
Four stages of IF amplification, detector and
AVC rectifier, noise limiter and meter rectifier, beat
frequency oscillator and buffer amplifier, IF output,
AF amplifier and output power stage, are among the
features of the SP-600-JX17, which are discussed
fully under separate headings in this manual.
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 head-
phone circuit when referred to an 8,000-ohm resis-
tive load provides signals attenuated approximately
15 db below the 600-ohm power output. Either head-
phones, loud speaker or both may be used for recep-
tion of signals.
The receiver i. f. output or audio-output, con-
nected to a suitable frequency-shift receiver conver-
ter and associated teletypewriter, provides for re-
corded copy of a
teletype signal. A CW signal may be
amplitude-modulated by an external tone generator
connected to the receiver, so that a steady, audible
(monitoring)
tone is always heard when the transmit-
ter carrier is on the air, whether signal intelligence
is
present, or not.
Asingle tuning control of special design per-
mits maximum traverse speed as well as exceptional
operating ease. It controls both the main and ver-
nier dials.
The main dial, in addition to being fre-
quency-calibrated, includes an arbitrary scale in hun-
dredths, while the vernier scale contains an arbi-
trary scale in units. These arbitrary scales, comple-
mented by the anti-backlash gear train which gov-
erns dial movement, provide extremely accurate log-
ging and resetability. A tuning lock assures positive
locking
action without affecting the frequency set-
ting.
Radiation is negligible and complies with re-
quirements for ship-board operation and for multi-
receiver
installations.
Although the antenna input circuit is designed
for
the coaxial cable connection of a wave antenna
system, a conventional single wire antenna may be
used.
The self-contained power supply of the SP-
600-JX17 is designed for operation on asingle phase
50 to 60 cycle alternating current power source. The
power transformer primary is provided with termi-
nals offering a range of line voltage from 90 to 270
volts.
The send-receive switch desensitizes the recei-
ver but leaves the power on to provide for instant
reception between transmissions.
The SP-600-JX17 is available as either a rack
model, suitable for a mounting in a standard 19"
relay rack, or as a cabinet model for table use.
1

SECTION II
CIRCUIT DESCRIPTION
GENERAL -The electrical circuitry of the SP-
600-JX-17 is shown schematically in Figure 9. A
block
diagram, Figure 2, is provided to illustrate 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 megacycles, consists
of two stages of RF amplification VI and V2; First
Mixer V5; First Heterodyne Oscillator V4; four
stages of IF amplification, V7, V9, VIO and Vll;
Detector, AVC Rectifier V14; Noise Limiter V15;
Beat Frequency Oscillator V13; IF output and AF
amplifier, V16A and V16B; Output Power Stage
V17, and the Power Supply System which includes
B
Power Rectifier V19, C Bias Rectifier C20 and Vol-
tage Regulator V18.
In the circuits for double conversion, used for
signal frequencies above 7.4 megacycles the Second
Mixer V6 and Second Heterodyne Oscillator V8 are
substituted for the gate tube V7.
Aprecise
rotary turret is used to change bands.
It associates the RF tuner, sub-assemblies of the
antenna coupling, the two-stage RF amplifier, and
the first heterodyne oscillator of the band selected
with the circuitry in the RF strip common to each
band. In this way, each RF tuner sub-assembly is
positioned directly adjacent to its respective tube
and gang section of main tuning capacitor CIA-CIH.
INPUT COUPLING - The antenna input coupling
provides an optimum match for a95-ohm coaxial
cable line connected
to antenna input connector J1.
On bands, 1,2, 3, and 4, the antenna RF transformer
is secondary-tuned by dual section CIA-CIB of the
main tuning capacitor; on bands 5 and 6, by section
CIA only. Acapacitor, such as C3 for band 1, is used
so that the antenna circuit tracking matches that of
the RF amplifier.
RF AMPLIFIER - The VI and V2 stages of the
RF amplifier are identical, VI is secondary-tuned
by dual section CIC-CID while V2 is secondary-
tuned by dual section CIE-CIF of the main tun-
ing capacitor. Complexed coupling is used in RF
stages to maintain a more constant level of signal
gain over the frequency levels of each band. High
image rejection ratios are achieved through the use
of three High Q tuned RF circuits and by double con-
version on the three higher frequency bands. The
high gain developed by two RF stages assures max-
imum sensitivity at high signal-to-noise ratios.
FIRST HETERODYNE OSCILLATOR (variable
V4) -
First Heterodyne Oscillator V4 functions
as a Colpitts oscillator for the three higher frequency
bands and as a tuned-grid oscillator for the three
lower frequency bands. Dual section CIG-CIH of
2
the main tuning capacitor provides for the variable
tuning of the oscillator. For single conversion, the
oscillator frequency is 455 Kc higher than the signal
frequency, while for double conversion the oscillator
frequency is 3.955
me higher than the tuned-in sig-
nal.
FIRST HETERODYNE OSCILLATOR (Crystal
Controlled V3) - For services requiring extremely
stable, fixed-frequency operation, a cristal control-
led
high frequency oscillator is provided. Instant
change-over from variable to crystal controlled os-
cillator with a choice of six crystal positions is
effected by a front panel XT ALS control. Asecond
front panel control marked Delta Frequency per-
mits atolerance adjustment of the crystal oscillator
frequency
over the +.005% (purchased crystal tol-
erance) range.
For double conversion, the conversion oscilla-
tor output from V3 is augmented by V 4.
Conversion oscillator output from V3 is avail-
able
at HFO output connector socket J8 at the rear
of the frequency control unit when the front panel
control is in a crystal position; but when the front
panel control is set to its EXT position, the conver-
sion oscillator
voltage for the receiver is that which
is
externally connected to J8.
INTERMEDIATE FREQUENCY AMPLIFIER ----;
Single conversion to 455KC is employed for signal
frequencies below 7.4 me. There are four stages of
IF amplification incorporating the Hammarlund-
patented filter circuit. Six positions of selectivity
provide 6 db bandwidths of .2, .5, 1.3, 3, 8, and 13 kc.
On the narrower bandwidth positions the crystal fil-
ter is in operation. The crystal phasing control pro-
vides extreme selectivity for the high attenuation of
closely
adjacent interfering signals. Double conver-
sion is
employed for signal frequencies above 7.4
mcs.
The signal is heterodyned to 3.955 me by the
First Mixer V5 and Heterodyne Oscillator V4, or V3
for
high image rejection. The 3.955 mcs signal is then
heterodyned to 455 KC by the Second Mixer V6 and
the 3.5 me Fixed Crystal-Controlled Oscillator V8
for selectivity. For double conversion, the tuned cir-
cuits and the 3.955 me IF transformer T2 assure ap-
propriate input to the Second Mixer V6. IF trans-
former TI in the plate circuit of V5 is resonant to
both 455 kc and to 3.955 mcs. For single conversion,
the 455 kc signal path is to 455 kc IF gate V7; for
double conversion,
the 3.955 me signal path is to
Second Mixer V6. The prime function of V7 is to
render the signal path through it an open circuit for
double conversion
and available to the signal for
single conversion.
The 3.5 me crystal-controlled heterodyne out-
put from V8 is available at IFO connector socket J6

at the rear skirt of the receiver, when the front panel
IFO switch is set to its INT position; but when the
IFO switch is set to its EXT position, the 3.5 mc
conversion oscillator for the receiver is that ex-
ternally connected to J8 since V8 is now inopera-
tive.
DETECTOR AND AVC - The VI4 tube is used as
a high level Detector and AVC rectifier. The AVC
circuit is
provided with separate time constants for
CW
and MCW operation. AVC and Diode output
terminals provide for connections in diversity ap-
plications.
The AVC bias developed is applied to VI,
V2, V6, V7, and V9, but the bias to VI and V2 is re-
duced through use of a voltage divider network (re-
sistors R48 and R53).
The BFO-AVC switch provides choice as to a
FAST or SLOW time constant. Since the switch
functions also
as a BFO switch, two positions, BFO
FAST and BFO SLOW, are provided.
BEAT FREQUENCY OSCILLATOR - The beat
frequency oscillator employs a high capacity Col-
pitts circuit which provide a high order of frequency
stability and minimizes oscillator harmonics. The
Beat Frequency Oscillator V13, is coupled into the
detector circuit through Buffer Amplifier V12, which
eliminates oscillator lock-in. A
front panel control
varies
the audio-beat frequency from zero to +3kc.
The beat frequency oscillator output from VI3
is available also at BFO connector socket J7 at the
'rear apron of the receiver when the front panel BFO
switch is set to either its FAST or SLOW INT BFO
positions; but when set to either of its FAST or
SLOW EXT BFO positions, the functioning beat fre-
quency oscillator for the receiver is that which is ex-
ternally connected to J7, since the output from V13
is
suppressed.
Front panel switch control MOD-CW renders
V13 operative for CW operation. An external switch
control connected to terminals BF of remote connec-
tor socket AN3102A-14S-2S (J4) on the rear skirt
may also be used to perform this function, since these
terminals are in parallel with the contacts of the con-
trol switch.
Alternate to the use of the beat frequency oscil-
lator to render a keyed-carrier CW signal intelligible,
alocal
tone generator may be externally connected
to terminals A and Bof J4 to amplitude moduh;tte
the CW signal. The use of alocal tone generator pro-
duces a
steady tone even when the received carrier
frequency drifts. J4 is furnished with connector plug
AN3108B-i4S-2P and cable clamp AN3057-6.
NOISE LIMITER - The noise limiter circuit V15
limits
the noise interference from ignition systems
or other sources of pulse-type noise. A separate
limiter control switch permits optional use of the
limiter on any mode of operation when pulse type
interference is present. .
AUDIO FREQUENCY AMPLIFIER - A resis-
tance-coupled amplifier triode VI6B amplifies the
audio-frequency signal from the detector.
AUDIO OUTPUT - The audio output to V17 is
transformer-coupled through a split balanced wind-
ing to deliver 2.0 watts undistorted output to a600-
ohm load. The split balanced winding permits bal-
ancing of the direct kind in the output circuit, as
used for teletype or similar service. A separate sec-
ondary winding provides attenuated audio signal
output for headphone 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
milliwatts to a600-ohm resistive load.
IF OUTPUT-A cathode follower, VI6A provides
a70-ohm
impedance source of intermediate fre-
quency (455kc) to socket SO-239 on the rear skirt
of the chassis. Plug PL-259, and angle plug adapter
M-359 used with coaxial cable RG-ll/U are not sup-
plied.
POWER SUPPLY - The power supply is an inte-
gral part of the receiver. It includes the Brectifier
V19
and Crectifier V20, together with their respec-
tive low-pass filters and Voltage Regulator V18. The
power transformer is provided with screw terminal
primary taps, covering apower 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 circuit.
TUNING METER - The tuning meter is used on
AVC operation to indicate the accuracy of tuning
and the relative strength of received signals. Depres-
sion of
the Meter Switch converts the meter circuit
for
indication of output level in db from 6milli -watts.
RF GAIN CONTROL AND POWER SWITCH-
The RF gain control is provided for manual control
of sensitivity to prevent overloading on strong sig-
nals when operating with the A VC-MANUAL
switch in the "MANUAL" position. This control
also operates when the switch is in the "A VC" po-
sition.
The Power "ON -OFF" switch is operated
at the counter-clockwise extremity of the RF gain
control.
SEND-RECEIVE SWITCH - The send-receive
switch desensitizes the receiver but leaves the power
"on"
to provide for instant reception between trans-
mission periods.
RADIATION - Advanced design and shielding of
the high frequency, second conversion crystal and
beat frequency oscillators has reduced radiation to
anegligible point so that interference of this nature,
common in multi-receiver installations, is reduced
to a minimum.
3

SECTION III
INSTALLATION
TUBES AND PACKING - After unpacking the
receiver see that all tubes are firmly in their sockets
and that all packing material is removed from the
receiver.
POWER SUPPLY - Make sure that the primary
tap lead at the bottom of the power transformer is
connected to the tap which most nearly agrees with
the 50 to 60 cycle power source voltage. Power con-
nector plug AN3108B-18-3S with cable clamp
AN3057-10 with power cord and plug are furnished
with the receiver.
ANTENNA - The input impedance at the antenna
socket, SO-239, is designed to match a 95-ohm coax-
ial cable line.
The plug connector PL-259, and angle
plug adapter M-359, supplied with the receiver, are
for use with RG-ll/U coaxial cable (not supplied).
SPEAKER - The speaker should be of the per-
manent-magnet dynamic type and should include
a
speaker voice coil to 600-ohm line-matching trans-
former 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 da-
mage from high transient peak voltages. For appli-
cations requiring the insertion of direct current con-
trol 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 re-
sistance balancing potentiometer, connected in its
place.
HEADPHONES - Either high or low impedance
headphones 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 rack
mounting. Top and bottom cover plates are supplied
for mounting in a standard 19-inch rack. The panel
is 10-1/2 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 re-
ceiver,
but will be supplied on special order for any
signal frequency within the range of from 2 to 30
megacycles. In order to insure correct crystal-con-
trolled frequency
operation, crystal units may be
ordered from THE HAMMARLUND MFG. CO.
The order should specify the signal frequency for
which
each unit is to be used. See note at end oi
page 30. To install crystals loosen the knurled
thumb screw on top of the Crystal Control Unit
T34 and push to the rear. Insert the crystals in
4
the sockets. 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 pro-
vided 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.
RELA Y CONNECTIONS - If external relay ope-
ration for the send-receive function is desired, con-
nection
may be made by soldering a twin conduc-
tor cable to the terminals of the Send -Receive switch
S9. In this case S9 is left in the Send or Open
position.
AVC
AND DIODE OUTPUT - In diversity ap-
plications,
the diversity feature is accentuated by
interconnecting the AVC (-) bus between receivers,
and utilizing a common ground (G) connection. This
AVC connection is
made when the IF or AF output
of the system is used to provide for the intelligence
due to aCW, MCW, or frequency-shift signal; but
for voice signals only the audio output from one re-
ceiver is used.
This is done by removing the DIODE
OUTPUT jumper on each receiver apart from one;
and connecting the negative (-) terminal of each to
that of the one whose terminals remain jumpered.
IF OUTPUT - The IF output socket SO-239 at the
rear skirt provides the signal at 455kc for diversity
receiving system use. Connector plug PL-259 and
angle plug adapter M-359 (supplied) should be used
with RG-ll/U coaxial cable (not supplied). The out-
put provided to a70-ohm resistive load is approxi-
mately 200 millivolts for normal sensitivity (2 micro-
volts input signal).
MASTER SLAVE CONNECTIONS - In diversity
applications the monitoring requirements imposed
on the operator are severe, but may be kept at amin-
imum by use of common conversion and beat-fre-
quency oscillators. Then the operator need concern
himself
mostly with the signal level in each channel
and the signal tuning of the receivers.
To
provide for V-3 crystal-controlled first heter-
dyne,
and/or V-8 3.5 me. crystal-controlled hetero-
dyne,
and/or V-13 beat-frequency oscillator output,
respectively, from the master to the slave receiver,
the HFO, IFO, and BFO sockets SO-239, at the
rear skirt, each furnished with plug PL-259, and
angle plug adapter M-359 for IFO and BFO only,

are interconnected. The coaxial cable RG-l1/U
suited for use is not supplied.
With the red front panel controls in each in-
stance on one receiver set to a red panel marking,
that receiver becomes the slave receiver, wherein its
V3 'HFO), V13 (BFO) and its V8 (IFO) are rendered
inoperative.
REMOTE CONNECTOR -The REMOTE connec-
tor J4 is furnished with connector plug AN3108-
14S-2P and cable clamp AN3057-6. Use terminals A
and Bof J4 for connecting alocal external tone
source to modulate aCW signal and use terminals
C and Dof J4 to perform the function of the CW-
MOD switch by another system panel switch, if de-
sired.
5
21
19 16 6
94
13
3
12
1. "SEND" "REC" switch
2. "IFO" "EXT" "INT" switch
3. "HFO" "V AR" "EXT"
"XTALS" "I" "2" "3" "4"
"5" "6" switch
4. "BFO-A VC" "EXT BFO"
"SLOW" "FAST" "INT BFO"
"SLOW" "FAST" switch
5. "PHONES" jack
6. "BAND CHANGE" control
7. "MEGACYCLES" window
8. Main tunding dial
9. Vernier Dial .
10. "TUNING" control
11.
"TUNING LOCK"
12.
Plastic chart
13. "HFO" "6. FREQ" control
14. "rtF
GAIN" control
15. "AVC"
"MAN" switch
16.
"METER" "RF" "AF" switch
17.
"MOD" "CW" switch
18. "BEAT OSC" control
19.
"SELECTIVITY" switch
20.
"XTAL PHASING" control
21.
"LIMITER" "OFF" switch
22.
"AUDIO GAIN" control
Figure 1. Radio Receiver, Front Panel View
5

SECTION IV
OPERATION
GENERAL -Before attempting operation of the
SP-600-JX17 receiver, the operator should thorough-
ly familiarize himself
with the functions and uses of
the various controls. When referring to the controls
in this description, the words in capital letters re-
present the part of 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
control, the word, SELECTIVITY in capitals indi-
cates the legend appearing adjacent to the control.
Reference
to photographs, Figs. 1 and 6, is suggested
while reading this description. Front panel controls
and dials are shown in Fig. 1 and rear controls and
terminals are shown in Fig. 6.
SELECTIVITY CONTROL -The SELECTIVITY
control is a6-position switch which selects three
crystals and three non-crystal degrees of selectivity,
ranging from extremely sharp for CW reception to
broad for good fidelity MCW operation. The SELEC-
TIVITY control dial indicates the 6 db bandwidth
at each setting.
PHASING CONTROL -The CRYSTAL PHAS-
ING control is adifferential type, variable air capa-
citor.
It permits adjustment of the crystal selectivity
characteristic for
high attenuation of closely adja-
cent channel interference on either side of the signal
frequency.
RF GAIN CONTROL -The RF GAIN control
varies
the overall gain of the receiver. This control
is operative
in either position of the AVC-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
indicated on the RF GAIN control dial.
AUDIO GAIN CONTROL -The Audio Gain con-
trol varies the input voltage to the audio amplifier.
This controlis also operative
in either position of the
AVC- MAN switch.
PHONE 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 con-
nected
to a separate secondary winding of the audio
output transformer, which provides an attenuated
signal for headphones. 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 cir-
cuit. This control is operative independently of any
6
position of any other control. See Section II, Cir-
cuit Description.
A
VC-MANUAL SWITCH - In the AVC position
the AVC-MAN switch applies automatic bias po-
tentials to the controlled RF and IF amplifier tubes,
thereby holding the audio output relatively constant
over awide variation in the strength of received sig-
nals.
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 afre-
quency 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 exceptionally strong signals
or
to reduce noise, but the RF meter is less effective
when
the RF GAIN control is below maximum set-
ting. In the MAN position the AVC potential is re-
moved from
the controlled tubes and the gain of the
receiver is manually controlled by the RF GAIN con-
trol.
CW-MODULATION SWITCH - The CW-MOD
control in the CW position energizes the beat fre-
quency oscillator.
In MOD position the beat fre-
quency oscillator is inoperative
and the conditions
are established for either voice
modulated or tone
modulated signal reception.
BEAT FREQUENCY OSCILLATOR -The BEAT
OSC control varies the tuning of the 455 kc Beat
Frequency Oscillator over a range from zero beat
to plus or minus 3kilocycles.
BFO-A VC SWITCH - The BFO-A VC control
in either the EXT BFO SLOW or INT BFO SLOW
positions connects an additional timing capacitor
to
the AVC circuit to accommodate the A VC circuit
to automatic CW keying, as compared to either the
EXT BFO FAST or INT BFO FAST positions, ef-
fective for MCW and frequency-shift reception. In
either FAST or SLOW INT BFO positions, the in-
ternal
BFO of the receiver is operative when the CW-
MOD switch is at CWo In either FAST or SLOW
EXT BFO positions, the BFO source connected to
the BFO connector at the rear skirt is used by the
receiver.
IFO SWITCH - The IFO switch in the INT po-
sition renders
the internal 3.5 mc crystal-controlled
conversion oscillator operative.
In the EXT posi-
tion
the oscillator is inoperative, since the IFO of
the master receiver (externally connected to the IFO
connector at the rear skirt) is used.
SEND-RECEIVE -The SEND-REC control is a
single-pole single-throw toggle switch.
In the SEND
position it desensitizes the RF amplifier, gate, second

mixer and 3.5 me oscillator tubes during trans-
mission periods.
TUNING CONTROL AND DIALS - The TUN-
ING control rotates the main tuning capacitor as
well as the main and vernier tuning dials. The main
dial has six frequency band scales, calibrated in meg-
acycles,
and an arbitrary outer scale. The vernier
dial
has an arbitrary 0 to 100 scale. The numeral
under the upper or fixed pointer of the main dial in-
dicates
the number of complete revolutions that have
been made by the vernier dial at any setting. Thus,
if the pointer for the outer scale of the main dial in-
dicates over the figure "4" and the vernier dial in-
dicates 87.6, the reading to log for this setting is
"487.6".
This precise mechanical vernier system di-
vides
the rotation of the main dial over each fre-
quency band into approximately 600 vernier divi-
sions,
with one-half division calibration points. Since
it is easy to estimate one-tenth divisions on the ver-
nier scale,
this divides each frequency band into ap-
proximately 6000 readable settings, providing ex-
treme accuracy in the logging and resetting of
stations.
TUNING LOCK - The TUNING LOCK, located
to the right of the TUNING control, provides apos-
itive lock for the tuning mechanism without affec-
ting the frequency setting when it is desired to pre-
vent accidental 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 con-
tact assemblies, from one frequency band to the next.
The turet has no stops and may be turned in either
direction. Apositive detent mechanism assures cor-
rect 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
indicator with the proper scale of the main dial.
CRYSTAL CONTROLLED HF OSCILLATOR-
The XTALS control selects one variable high fre-
quency oscillator operation, anyone of the six crys-
tal positions. Correspondingly numbered crystal
sockets are provided in the Crystal Control Unit. In
its EXT position, the crystal-controlled first conver-
sion oscillator source is connected
to the HFO con-
nector at the rear skirt. See Section III Installation.
The DELTA FREQ. control compensates for the
small crystal frequency tolerance.
METER SWITCH -The METER switch is adou-
ble-pole,
double-throw toggle switch with spring re-
turn to the RF position. See Section II, Circuit De-
scription,
Tuning Meter.
TUNING METER CONTROLS - The METER
ADJ 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
a
reading 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 AVe position. Depression
of
the METER switch to the AF position converts
the meter circuit for indication of the AF power out-
put level in db from 6milliwatts. This switch is
spring-returned to the RF position when released
and should not be depressed 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 precaution may result in damage to
the meter. The meter ADJ AF control is used to reg-
ulate the meter current when operating on the AF
scale. This control is adjusted to obtain a 0 db read-
ing on the AF scale of the meter and is made with
the audio power output from the 600-ohm AUDIO
OUTPUT terminals adjusted 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 advance this control to "10". Note that
the dial lamps light. 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. In-
sert 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
A VC-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 de-
sired,
as indicated by the MEGACYCLES dial, ad-
vance the AUDIO GAIN control until some noise is
heard.
Turn the TUNING control to indicate the de-
sired frequency
on the main dial and tune the signal
for maximum response or indication on the RF
Meter. At resonance the main dial reading should be
within one-quarter of one percent of the signal fre-
quency.
Re-adjust the AUDIO GAIN control for the
desired output level and as required to prevent over-
loading. Carefully
tighten the TUNING LOCK by
turning clockwise, if desired. The SELECTIVITY
switch may be turned to the 8 kc or 13 kc position
for improved high frequency response if the signal-
to-noise
ratio is sufficiently high. If the noise level
is high,
the SELECTIVITY switch should be turned
to the bandwidth which provides the most intel-
ligible reception
and the LIMITER switch should
be
thrown "on". If the SELECTIVITY switch is used
on one of the XT AL positions, the XT AL PHASING
control may be adjusted to either side of its center
position to attenuate an adjacent interfering signal.
The
RF GAIN control may be turned down some-
what 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 ope-
7

ration and indicates only when the AVC- MAN
switch is on AVC. When searching for very weak
signals
the CW-MOD switch may be thrown to
CW and the BEAT OSC control set at "0". 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 fre-
quency for which crystals have been provided. See
Section
III, Installation. Turn the XTALS switch
to the numeral corresponding to that on the panel
chart for the desired signal frequency. Set the main
tuning dial to the signal frequency and adjust the
6. FREQ control to obtain zero beat with the CW-
MOD switch on CW and the BEAT OSC control at
"0". Throw the CW-MOD switch to MOD and ad-
just the TUNING control for maximum RF Meter
indication or for maximum 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 sig-
nal 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
8
output level by the AUDIO GAIN control when on
AVC and by the RF GAIN control when on MAN.
The
RF Meter does not operate on the MAN posi-
tion.
The SELECTIVITY switch may be used in the
XT AL positions, as found desirable, to reduce noise
or to provide rejection of an interfering signal. The
XTAL PHASING control is adjusted for minimum
interference from an adjacent, interfering signal. If
interference of this kind persists, further discrimi-
nation between the desired and the undesired sig-
nals 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 Re-
ception 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.

SECTION V
MAINTENANCE
GENERAL - This receiver is designed for contin-
uous duty and should normally require little atten-
tion beyond the replacement of tubes. An occasional
cleaning of
the gear teeth in the gear train is recom-
mended to prevent a heavy accumulation of dust
which may cause calibration error and improper op-
eration of the gears. This may be done with a small
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 fa-
cilitated if the contents of this instruction book are
throughly digested.
Some sectionalizing of faults is possible, if the
fault is not existent on all of the frequency bands.
Non operation of only the three lower 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 af-
fected, refer
to HF Oscillator and RF Coil Assemblies
in this section.
Visual evidence of
trouble is usually a burned
or darkened resistor, which is usually the result of
excessive
current due to a short circuited capacitor
or tube element on the load side of the resistor. In
such acase, the short circuited capacitor or tube and
the resistor should be replaced as indicated. Refer
to Figures 7 to 12 and Section VII for location and
values of components. If the checks on tubes, fuses
and visual inspection fail to disclose the fault, the
tube socket voltages and resistances should be mea-
sured and checked against the value given in Tables
1 and 2. Any appreciable departure beyond a normal
variation of approximately 15 percent from the
values in these table will generally indicate the com-
ponent or circuit at fault. If the foregoing does n6t
reveal the fault, then a stage by stage check of amp-
lification
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
IF oscillator coil assembly is found defective, only
the replaced unit need be realigned. Follow the align-
ment procedure in Section VI, for the unit involved.
The IF Transformers, Crystals Filter, Beat Fre-
quency Oscillator and the 3.5 mc Crystal Control-
led
assemblies are mounted on the chassis, independ-
ently of their respective shields. The shield can as-
semblies
are easily removed for inspection of these
units, without disturbing the soldered connections',
When replacing these shields, make sure that the
grounding springs are in place on the inductance ad-
juster screws before the shield is installed.
VACUUM TUBES - Weak or defective vacuum
tubes are the most common cause of decrease in sen-
sitivity, faulty performance or failure of operation in
areceiver. In case of such faults, first remove the
tubes and check them in a tube tester of reliable de-
sign.
If a tube tester is not available, substitution
of anew tube for each tube type and position should
be tried. See Figures 2 and 3, Such substitution is
best made, one tube at a time in order that the faulty
tube may be detected by the improvement or res-
toration of performance by the new tube.
LOCATING FAULTS - If the dial lamps do not
light when the power switch is turned on, check for
a
blown line fuse, Fl and replace it at the rear of the
receiver from the spare fuses. If the dial lamps light
but there is no sound at all in the headphones or
speaker, check for ablown, minus Bfuse, F2. If
blown, replace. In replacing fuses, make sure that
only a1.6A Fusetron is inserted in the line fuse hold-
er and that only a 3/8 ampere fuse is inserted in the
minus Bfuse holder. Should neither fuse be blown,
or if replacement of the fuses does not resotre opera-
tion,
the receiver should be removed from its rack
and inspected for visual signs of trouble. The rack
model receiver is provided with bottom imd top cover
plates which should be removed for purposes of in-
spection and repair.
IF TRANSFORMERS - If fault is traced to one
of the variable coupled IF transformers, T4 or T5,
check
whether the fault exists on all positions of the
selectivity 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 imper-
fect soldered
connections at the coil and switch ter-
minals and check the switch contact involved. If
faulty operation localized at one transformer exists
on all positions 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 T4 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 screw
with ascrew driver to prevent turning the screws and
losing the alignment adjustment and loosen the ten-
sion
nuts, using another small screw driver engaging
one of the slots. When replacing these shields and
tension nuts, employ the same method and tighten
the tension nuts just enough to prevent the adjust-
ing screws from working loose.
BEAT FREQUENCY OSCILLATOR -To remove
the beat frequency oscillator T6, it will be necessary
9

to set the crystal selector switch S2, on its number
3 position 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. Be careful to
avoid overheating the wire of the shielded cable since
this wire is insulated with polystyrene and is easily
damaged 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 ohm meter
the connection 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 12. Now remove the two screws
holding the BFO shield can to the chassis and the
two screws at the underside of the chassis and re-
move 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 brackets, adjust
the unit and shaft brackets 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 A VC-MAN
switch on AVC, 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 3 kc position
and check the output beat frequency against a known
audio frequency source such as a good audio oscil·
lator.
If the beat frequencies obtained at each 3 kc
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 adjust-
ment by the top screw of the BFO unit each time
until the above range is realized. One set screw
should be used just tight enough to allow the drive
shaft to operate the BFO shaft until the range is cor-
rect and then tighten both screws.
CRYSTAL SWITCH ADJUSTMENT -If the me-
chanical drive of the crystal control switch has been
disturbed, it should be adjusted as follows: Care-
fully slide
the switch shaft through the disc and into
10
the rigid coupling and, being careful not to turn the
switch, tighten the four set screws in the rigid coup-
ling,
with the knob indicator on the number 3po-
sition as originally set under Beat Frequency Oscil-
lator. Now
set the crystal switch on the number 1
position and, holding the disc in acounter-clockwise
direction so
that the end of the slot in the disc is a-
gainst 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 a slight amount
of play when tried with the thumb and forefinger.
When so adjusted, tighten the set screws.
CRYSTAL CONTROL UNIT - If it has been de-
termined that the Crystal Control Unit is defective,
it will be necessary to remove the unit for repair or
replacement. Refer to Figure 11 and 12 and unsolder
the lead of resistor R71 from switch S3 on the gear
plate. Unsolder the black, black-white, blue-red and
red-white leads of the crystal control unit from termi-
nal 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 Frequency Oscillator. Loosen set screws and re-
move the delta C control 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 sufficiently to permit re-
moval 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 strain on the delta C shaft, or the delta C
capacitor may be damaged. Remove 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 crys-
tal unit box. When the unit is to be replaced, follow
the reverse of the above procedure. Follow the pro-
cedure
under Crystal Switch Adjustment to properly
reinstall the switch mechanism.
HF OSCILLATOR AND RF COIL ASSEM-
BLIES - If faulty operation occurs in only one fre-
quency 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-clock-

wise. This will place the band coil assemblies parallel
and at the bottom of the tuning unit. Now remoVe
the two springs holding one coil assembly in the tur-
ret and carefully remove it by sliding it towards you
and off the tongues of the shields. It is best to re-
move only one coil assembly at a time and inspect
it for defects or substitute a replacement assembly
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 procedure until the faulty assembly is found.
In checking these assemblies, first check for contin-
uity of the coils, particularly the small primary coils
as in the RF Input assemblies, which 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 as-
sembly nearest the coil is toward the front of the re-
ceiver.
MIXER PLATE COIL ASSEMBLY -Trouble in
the Mixer Plate Coil Assembly Tl, is indicated if
the input required at pin 7of V5 is found to be great-
ly different than the values shown in Table 4, and the
gain from pin 7of V6 is normal. To obtain access to
the components of the mixer plate coil assemblies it
is necessary to remove the crystal control unit and
the filter assembly as described under Crystal Con-
trol Unit. The cover plate and shield of Tl may then
be removed for replacement of adefective compo-
nent. If the entire assembly is to be replaced, it will
be necessary to unsolder all of the leads at both the
bottom and top terminal boards of the unit. Refer
to Figure 11 for components and wiring of Tl.
RF TUBE PLATFORM - If the receiver fails to
perform normally on any of the six frequency bands
and the previous tests indicate that performance of
the IF and audio frequency amplifiers is normal, (in-
cluding the gain check in accordance with Table 4
for
the input to pin 7of V5) the fault is inclicated to
be in the RF Tube Platform or in the main tuning
capacitor. Before removing the RF Tube Platform,
it is advisable to remove the top shield cover and
inspect the main tuning capacitor connections. Re-
fer
to Figures 8 and 11. Observe that the tuning ca-
pacitor is operating properly. when the tuning con-
trol is rotated. Using a miniature tube adapter, see
Section
VI alignment, apply a modulated RF test
signal successively to pin 1of VI and V2 and to pin
7of 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
6 should be indicated for each stage and loss of sig-
nal will indicate the section to be investigated for
the fault. No signal output, when the input signal is
applied to pin 7of V5, will indicate trouble in the HF
oscillator section of the unit. With the covers re-
moved from the tuning capacitor and Tl, refer to
Figure 11 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 S3. Turn the Band
Change control one-half turn from any band posi-
tion in order to have the band switch contacts dis-
engaged and leave the band switch in this position
until the RF tube platform is replaced, otherwise ir-
reparable damage to the switch contacts will occur.
Remove
the four strews 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.
MAIN TUNING CAPACITOR - If it is necessary
to replace the main tuning capacitor, the procedure
is
as follows: Remove the top cover and unsolder the
leads of the capacitor as described under RF Tube
Platform. Bring the capacitor 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 capaci-
tor and gear plate. The fr:ont capacitor plate is lo-
cated and held in position 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 supporting screw and spacer. The
capacitor may now be moved to the rear, to dis-
engage the dowel pins, and lifted from the receiver.
Follow
the above procedure in reverse when replac-
ing the capacitor.
11

SECTION VI
ALIGNMENT
The alignment of a modern communications re-
ceiver requires precision instruments and a thorough
knowledge of the circuits involved. Since this re-
ceiver is a double super-heterodyne type, the align-
ment procedure is even more involved than usual.
Under normal service the receiver will stay in
alignment for extremely long periods of time, conse-
quently realignment should not be attempted unless
all other possible causes of a particular trouble have
been eliminated. When it has been determined that
any realignment should be made, a great deal of
caution should be exercised in making the adjust-
ments, since any required readjustment should not
entail more than a slight angular motion of the ad-
justing screw.
ALIGNMENT OF THE IF STAGES
The low frequency IF should be aligned first.
The recommended method for aligning the low fre-
quency IF involves the use of a sweep frequency sig-
nal generator and an oscilloscope. Since these instru-
ments are not available at the average service sta-
tion the alternate method using an amplitude mod-
ulated signal generator 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 V5 through a capacitance of
approximately .01 mfd. A miniture tube adapter will
be required to make the mixer grid connection avail-
able. A
suitable adapter, A/N No. CV-49519, is avail-
able as Part No. 977 from Alderi Manufacturing Co.,
117 N.
Main Street, Brockton, Mass. An output me-
ter should be connected across the output of the re-
ceiver or the speaker voice coil. The receiver controls
should now be set as follows:
the 3 kc position and advance the RF Gain control
to maximum. Set the signal generator frequency to
455 kc and adjust its output until some deflection
is noted on the output meter. Refer to figure 3for the
location of the various alignment adjustments. Ad-
just L42, L41, L39, L38, L36 and L32 for maximum
output, reducing the signal generator output and the
RF Gain control as reqtlired to prevent overload or
excessive output. Now turn the selectivity switch
to the narrowest position, .2 kc, and adjust the sig-
nal generator frequency 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 i.f. alignment,
unless it should be re-check this establishment of
crystal frequency to make sure that the signal gen-
erator frequency has not drifted during the align-
ment. The selectivity switch is now turned to the 3
kc position and L42, L41, L39, L38, L36 and L32
are again adjusted for maximum output. Before
changing this set-up the BFO should be turned on
by throwing the CW-Mod switch to CW and check-
ed 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 un-
modulated.
The Procedure for the visual method of aligning
the low frequency IF, using the double image sys-
tem, should be the same as the above except that
the adjustments are made for both maximum ampli-
tude and coincidence of the oscilloscope images. The
oscilloscope vertical input should be connected a-
cross the diode detector load resistance, from the
junction of R64 and R65 to chassis.
The signal generator should be modulated 30
percent at 400 cycles. Turn the selectivity switch to
12
Control
Selectivity
Send -Receive
CW-Mod
Phasing
AVC-MAN
Audio Gain
RF Gain
Band Switch
Dial
BFO-AVC
IFO
Position
See Text
Receive
Mod
Arrow
Man
Set for approx. 20 volts
output
See Text
1.35-3.45 mc
2.5 mc
Int. Bfo fast
Int.
The high frequency IF should be aligned next.
Set the band switch to the 7.4 -14.8 mc band. The
selectivity switch should be in the 3 kc position.
Adjust the signal generator frequency to 3.955 mc
and adjust L31, L33 and L34 for maximum output.
The 3.5 mc crystal used in the second conver-
sion oscillator circuit is held to a very close frequency
tolerance and may be used as a frequency 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 os-
cillator tube V8. This test should, of course, be re-
moved except while in use as a frequency standard.

ALIGNMENT OF THE RF
AMPLIFIER & HF OSCILLATOR
To adequately align the RF amplifier and HF
Oscillator an accurately calibrated signal generator
and an output meter are required. The frequencies
required are shown
in Table 3. The location of the
adjustments is shown in Figure 3. The location of the
3 and Figure 3 should 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 gene-
rator is coupled to the antenna input terminal
through a100-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 whould be set as
follows:
Control
Selectivity
Send-Receive
CW-Mod
AVC-Man
Audio Gain
RF Gain
Band Switch
Limiter
HFO
Position
3kc
Receive
Mod
See Text
Set for approx. 20
volts output
See Text
Set for band to be
aligned
Off
Var
Set the receiver and signal generator dials to
.56 mc. The RF Gain control should be set at max-
imum and the AVC- MAN switch set on AVC. The
HF Osc. L adjustment shown in Figure 3, should
now
be set for maximum output. Then the Ant., 1st
RF and 2nd RF L adjustments should be set for max-
imum output. The receiver and signal generator dials
are now set to 1.3 mc and the C adjustments, shown
in Figure 3, should be adjusted for maximum output
in the same order, beginning with the Osc. Cad-
justment and then making the C adjustments for
the Ant, lst"RF and 2nd RF. This procedure should
be carefully repeated until no increase in output can
be realized. The AVC-MAN switch should then be
set to MAN and the signal generator should be set
for approximately 3microvolts. The L and C adjust-
ments 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.
13

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 sig-
nal input. Audio Gain control at minimum and CW-
MOD switch on "CW".
SOCKET PIN NUMBERS
MODE OF
TUBE
123456789
OPERATION
VI 1-6.3
ac
-
200
95
- - - r-f gain max
VI
-41
-6.3
ac
-
260 245
- - -r·f
gain min
V2
-1
-6.3
ac
-
210
95
---r-f
gain max
V2
-41
-6.3
ac
-
260 245
---r-f
gain min
V3
/06.3
ac 285 0r-f
gain max, -- - --val'
freq osc
operation
V3
12.5 --6.3 ac
285
140 - - -r-f gain max,
crystal freq
control
V3
0- - 6.3 ac
305
0---r-f gain min,
val'
freq osc
operation
V3 -12.5 --6.3
ac
300 140 -- - r-f
gain min,
crystal freq
control
V3
0- - 6.3 ac
285 0--r-f gain max,
external oper-
ation
V4
130 -6.3 ac -
130 -- - - r-f gain max or
min.
V5
-1.2 6.3
ac -140 110 - - -r-f
gain max
or min
V6 --6.3
ac
-
225 -
-1
--r-f gain max,
freq below 7.4
me
V6 - - 6.3
ac
-
260 -
-55
--r-f
gain min,
freq below 7.4
me
V6 - - 6.3
ac
-
225
80
-1
--r-f
gain max,
freq above 7.4
me
V6 --6.3
ac - 260
75
-55
- - r-f
gain min,
freq
above 7.4
me
V7
-1
-6.3 ac -
215 125 3.4 --r-f gain max,
freq below 7.4
me
V7
-54
-6.3
ac -
265 245 .4
--r-f
gain min,
freq below 7.4
me
V7
-1
-6.3
ac
-
215 0 0 - - r-f gain max,
freq above 7.4
me
14

SOCKET PIN NUMBERS
MODE OF
TUBE 1 2 3456789
OPERATION
V7
-54
-6.3
ac
-265 0 0 - - r-f
gain min,
freq
above 7.4
mc
V8 0-6.3
ac -- - ---freq below 7.4
mc, i-f-o switch
at internal.
V8 75 -6.3 ac -75 -17
-- - freq
above 7.4
mc, i-f-o switch
at internal
V9 -1 -6.3
ac
-205 90 ---r-f
gain max
V9 -54
-6.3
ac
-260 150 - - -r-f
gain min
VI0 -1.25 -10
6.3 ac
-200 92 -- - r-f
gain max
VI0 -54 -10
6.3 ac
-240 140 ---r-f
gain min
Vll -7.8
-6.3
ac
-210 140 ---r-f
gain max
Vll -7.8
-6.3
ac
-235 140 ---r-f
gain min
V12 0-6.3
ac
-192 72 .9 --r-f
gain max
V12 0-6.3
ac
-215 80 1--r-f
gain min
V13 20 -6.3 ac - 20
-3.3
- - -r-f
gain max
or
min
V14 --6.3
ac
-
22
----r-f
gain max or min
V15 --6.3
ac
-- - - - -r-f
gain max or min
V16 50 -1.5 - - 210 -6.4 6.3
ac
r-f gain max
V16 57 -
1.6
- - 240 -7.4 6.3
ac
r-f gain min
V17 --260 228 --6.3
ac
12 -r-f
gain max
V17 - - 280 265 --6.3
ac 13 -r-f gain min
V18 150 - - -150 ----r-f
gain max or min
V19 -300 -----300 -r-f
gain max,
5.0
ac pin 2 to
pin 8
V19 -320 - - - - -320 -r-f
gain min,
5.0 ac pin
2
to pin 8
V20 -
-96 6.3 ac
- - -
-96
- - r-f
gain max
V20 - -97
6.3 ac
- - -
-97 - - r-f
gain min
15

TUBE SOCKET TERMINAL RESISTANCE-TABLE 2
Audio Gain Control at maximum, RF Gain Control
at minimum. Limiter Switch "OFF". CW-MOD
Switch on "CW". AVC-MAN Switch on "AVC".
Resistance
to chassis. Measurements made with
Weston Model 663 Volt-Ohmmeter.
!
Tube removed from socket under measurement.
SOCKET PIN NUMBERS
MODE OF
TUBE
1 2 3456789
OPERATION
VI
1800K
0-0
16.7K
50K
0--
V2
1800K
0-016.7K
50K
0--
V3 23K 0--
15K 17K
0--
Crystal freq
control positions
1-6
V3 0 0 --15K infin- 0--Val'
freq or
ity
external
V4 infin- infin- -0infin-
47K
0--
crystal freq
ity
ity
ity
control posi-
tions 1-6
V4 19K infin- -0
infin-
47K 0--val'
freq osc
ity
ity
operation
V5 47K
150 -0
19K
22K
26K --
V6 22K 0-0
17.4K
infin<
nOOK
- -
freq bands
ity
below 7.4 me
V6 22K 0-017.4K 37.4K
nOOK --
freq bands above
7.4 me
V7 980K 0-017.4K infin- 390 --
freq bands above
ity
7.4 me
V7 980K 0-0
17.4K
48K
390 --
freq bands below
7.4 me
V8 infin- infin- 20
62K
9.5K
0--
freq bands above
ity ity
7.4 me, i-f-O
switch at internal
V8 infin- infin- 20infin-
9.5K
0--freq
bands above
ity ity ity
7.4 me, i-f-O
switch at external
V9 nOOK
0-0
17.5K
9.5K 0- -
V10 nooK 117K
--
17K 9.5K 0--
vn 93K
0-0
17.5K 19K
0- -
V12 1.2 0--
17K 61K 100 - -
V13 ----
160K lOOK 0--
V14 0
816K
-0
15.6K
0
196K --
V15
69K infin- -0infin- 0
196K
- -
ity ity
V16 125K
500K
1K
00 17.4K 470K
680 -
V17 0015.6K
15.2K 470K
infin- -360 -
ity
V18 n8K
-- -
20K
-0- -
V19 -15.8K 042 -40 -
15.8K
-
V20 49K
65K
-0 49K
0
65K
--
16

3.5MC
CRYSTAL CONTROLLED TO
BFO J7
V8
TO
FFO
I FO J6
6C4
VI3 VI2
VI4B
V4
VFO
BFO
BUFFER AVC
6C4
6C4
6BA6· 6AL5
V6
MIXER
.
TO
6BE6 ,
((;),' .
REMOTE J4
,
.... ~
((;)'
0)'
~\\j'
"?/~tJ
,
,..
VI
V2 V5
,.
V9 VIO
VII
VI4A
VI6B
VI7
,,
RF
RF
MIXER,' IF
AMP
IFAMP DRIVER DET
AFAMP
OUTPUT
6BA6
6BA6 6BE6
's;>
6BA6 6BA6 6BA6
6AL5 12AU7
6V6GT
~''t, ((;)((;)!
C'"
\.
"'/~
\
V7
/
GATE
6BA6
V3
VI6A
TO IF
VI5A VI5B
FFO
TO HFO J8
IF OUT
OUTPUT
IMITER METER
6AH6
12AU7
J2
6AL5
6AL5
CRYSTAL CONTROLLED
TO OUTPUT
LEVEL METER
V20
C
RECT
6AL5
VI9
B
RECT
5R4GY
Figure 2
BLOCK DIAGRAM
VIS
V REG
OA2
---Signal path common to all frequencies
-- - -Signal path for frequencies above 7.4 mc
_ •• __ • /I II II II below7.4mc