Hallicrafters HT-44 User manual

1
SUPPLEMENT
TO
OPERATION AND MAINTENANCE
MANUAL
HALLICRAFTERS
HT-44
WDØGOF 02/28/2019

2
SUPPLEMENT TO
OPERATION AND MAINTENANCE MANUAL
HALLICRAFTERS HT-44
INTRODUCTION
The HT-44 was produced for 1 year in 1962. It is a 17 tube AM-CW-SSB transmitter/exciter covering 80
through 10 meters. The power output is 100-130 watts PEP SSB, 100-130 watts CW and 25 to 35 watts AM.
The features include VOX, CW break in, PTT, AALC and front panel control of slave (tranceive) or
independent transmitter when used with the companion SX-117.
Over the years technical data on this system has scattered to the four winds. The purpose of this document is to
assemble as much technical information as can be found into one clear and easy to read document. We will take
a systematic approach to the repair and restoration process. The prime assumption will be that nothing works
and will proceed from there.
This document is available free of charge and can be downloaded from the Hallicrafters users’ group
https://groups.io/g/HallicraftersRadios or https://wd0gof.com . This document is the intellectual property of the
author, Walter A. Cates, WDØGOF. Unless specifically credited to a contributor all processes, ideas, drawings,
data sheets and opinions contained here are those of the author.
Special thanks to Bernie, WDØGMD for the loan of his HT-44 for test and research for writing this document.

3
SUPPLEMENT TO
OPERATION AND MAINTENANCE MANUAL
HT-44
Contents
INTRODUCTION.......................................................................................................................................................................2
1, REPAIR AND REFURBISHING................................................................................................................................................6
1-1, RECAPPING...................................................................................................................................................................6
1-2, AFTERMARKET MODIFICATIONS..................................................................................................................................6
1-3 TEST EQUIPMENT REQUIRED........................................................................................................................................6
1-4, INITIAL POWER UP.......................................................................................................................................................7
1-4-1, VOLTAGE VARIFICATION TESTS ............................................................................................................................8
1-4-2, INITIAL BIAS ADJUSTMENT ...................................................................................................................................8
1-5, OSCILLATORS ............................................................................................................................................................... 8
1-5-1 CARRIER OSCILLATOR TEST AND VERIFICATION....................................................................................................8
1-5-1-1, CARRIER OSCILLATOR FAULT ANALYSIS.........................................................................................................9
MODE / VOLTAGE CHART........................................................................................................................................9
1-5-2 HETRODYNE OSCILLATOR...................................................................................................................................... 9
HET OSC VOLTAGE CHART.......................................................................................................................................9
1-5-3 VFO ........................................................................................................................................................................9
1-5-3-1 VFO TEST AND ALIGNMENT..........................................................................................................................10
VFO VOLTAGE CHART............................................................................................................................................10
1-6, DRIVER/PA PRETEST & SETUP....................................................................................................................................11
1-6-1, DRIVER & PA PRESET ..........................................................................................................................................11
1-6-2, 6.5 MHZ TRAP.....................................................................................................................................................11
1-7 FIRST MIXER, 6-6.5MHz I.F., SECOND MIXER..............................................................................................................12
1-7-1, MIXER/I.F. SETUP & ALIGNMENT .......................................................................................................................12
1-7-1-1, INJECTION LEVEL PRETEST...........................................................................................................................12
1-7-1-2, 6MEG ALIGNMENT ......................................................................................................................................12
MIXER/IF VOLTAGE CHART ...................................................................................................................................12
1-8 DRIVER / PA ALIGNMENT............................................................................................................................................13
1-8-1, DRIVER/PA COIL ADJUSTMENTS.........................................................................................................................13
1-8-2, 10 METER ADJUSTMENT.....................................................................................................................................14
1-8-3, 15 METER ADJUSTMENT.....................................................................................................................................14
1-8-4, 20 METER ADJUSTMENT.....................................................................................................................................14

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1-8-5, 40 METER ADJUSTMENT.....................................................................................................................................14
1-8-6, 80 METER ADJUSTMENT.....................................................................................................................................14
1-9, PA NEUTRALIZATION..................................................................................................................................................14
1-9-1, NEUTRALIZATION PRE-TUNE ..............................................................................................................................15
1-9-2, NEUT. SET UP......................................................................................................................................................15
1-10, CARRIER DRIVE LEVEL ..............................................................................................................................................15
1-10-1 CARRIER LEVEL ADJUSTMENT............................................................................................................................15
1-11, MODULATION AND CARRIER SUPPRESSION............................................................................................................16
1-11-1 CARRIER SUPPRESSION TEST AND ADJUSTMENT..............................................................................................17
1-11-2 UNWANTED SIDEBAND REJECTION...................................................................................................................18
2 SUBSYSTEM ADJUSTMENT & TROUBLE SHOOTING...........................................................................................................19
2-1 MICROPHONE AUDIO .................................................................................................................................................19
2-1-1, VOLTAGE CHART.................................................................................................................................................19
2-1-2, SIGNAL LEVEL CHART..........................................................................................................................................19
2-1-3, REFERANCE VOLTAGES.......................................................................................................................................19
2-2, VOX TEST AND TROUBLESHOOTING..........................................................................................................................20
2-2-1, VOX TEST SETUP .................................................................................................................................................21
2-2-2, VOX TEST.............................................................................................................................................................21
2-2-2-1, VOX SIGNAL & VOLTAGE MEASURMENTS ..................................................................................................21
2-2-3, ANTI-TRIP............................................................................................................................................................22
2-2-3-1 ANTI-TRIP TEST.............................................................................................................................................22
2-2-4 DRIVER/PA TROUBLESHOOTING..........................................................................................................................23
2-2-4-1 STATIC DC VOLTAGES ...................................................................................................................................23
2-2-4-2 SIGNAL DRIVE LEVELS...................................................................................................................................23
2-2-5 AALC.....................................................................................................................................................................24
2-2-6, DRIVER TUNING SETPOINTS ...............................................................................................................................24
2-2-7, GOING ON THE AIR WITH THE 44.......................................................................................................................25
2-2-7-1, BIAS ADJUSTMENT ......................................................................................................................................25
2-2-7-2, PA OUTPUT FINAL ADJUSTMENT.................................................................................................................25
3, ATTACHMENTS..................................................................................................................................................................26
3-1, ERRATA SHEET TUBE MATCHING...............................................................................................................................26
3-2, INTERNAL R/T RELAY MOD ........................................................................................................................................27
3-3, DATA SHEETS .............................................................................................................................................................28
3-3-1 MIC AUDIO DATA.................................................................................................................................................28
3-3-2, VOX SIGNAL & VOLTAGE MEASURMENTS..........................................................................................................29

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3-3-3,.CARRIER OSC.......................................................................................................................................................29
MODE / VOLTAGE CHART......................................................................................................................................29
3-3-4 HET OSC ...............................................................................................................................................................29
HET OSC VOLTAGE CHART.....................................................................................................................................29
3-3-5 VF0.......................................................................................................................................................................29
VFO VOLTAGE CHART............................................................................................................................................29
3-3-6, MIXER-IF .............................................................................................................................................................29
MIXER/IF VOLTAGE CHART ...................................................................................................................................29
3-4 MISC............................................................................................................................................................................30
3-4-1, ANALYZER/SCOPE PICKUP ..................................................................................................................................30

6
1, REPAIR AND REFURBISHING
This document is written with the assumption that the restorer has a basic understanding of circuit and tube theory.
In Section 1 you will find the test and alignment procedures. If a particular process does not function as
described you will proceed to the appropriate subsection of section 2, SUBSYSTEM TROUBLE SHOOTING
for fault analysis. Section 3 ATTACHMENTS contains additional information on the system and a subsection
of data sheets. You can copy the data sheets to record data as you perform system analysis. A complete
cleaning and mechanical inspection are always advised. Cleaning of the rotary switches and the relays is of
particular importance. Go to https://wd0gof.files.wordpress.com/2019/02/rig-cleaning.pdf for the process I have
used for 20 years. After a thorough cleaning do a close visual inspection. Look closely for broken or burned
components. Check the rotation of the controls and mechanical stops of the main tuning dial. Try to eliminate
the mechanical problems first. Inspect L28 for heat deformation on the end furthest from the chassis side panel.
This is a high failure rate item when the rig is mistuned or misused.
1-1, RECAPPING
There is one dual section capacitor that is a must replace item. C91A and B can be replaced with custom made
dual capacitors or two individual capacitors positioned under the chassis. Either way you should seek out very
low ESR rated capacitors. ESR’s of 0.5 ohm and lower are available. I prefer ESR of 0.05 or less. There is
much discussion about the Plastic Mica and the Ceramic Tubular caps used in the 44. You must follow your
heart here. I do not replace them unless I find a bad one.
1-2, AFTERMARKET MODIFICATIONS
It is rare to find a unit that has not been modified or “improved” by a previous owner. As a general rule you are
better off striping all the mods and returning the rig to its original condition.
1-3 TEST EQUIPMENT REQUIRED
•Dummy key plug (key plug with no connections).
•Scope, 100mhZ BANDWIDTH, 1X, 10X PROBES
•Two multimeters, no need to spend a lot of money here. One small VOM with a 2.5 vdc and 10vdc range
dedicated to plate current setup and monitoring. The second meter can be a Harbor Freight $6 - $10 DVM.
•Frequency counter, 1.6 –40MHz
•Dynamic microphone, See https://wd0gof.com/hallicrafters-radio/technical-discussions/ht/ht-miscellaneous/ and click on SR & HT
SERIES MIC SELECTION.
•Telegraph key
•Hf Signal generator
•Dummy load/wattmeter
•Microphone patch cable
•Driver tube capacitive pick-up (see 2-2-4)
As a general rule I have tried to eliminate specialized or expensive test equipment. Systems like the HT-44
cause me to make acceptation. The phasing adjustments of the balanced modulators as described in the manual
can be quite tedious. When you have completed the process all you really know is that you have completed the
process. A spectrum analyzer turns the 10minute to ½ hour process into a minute and a half process with
definitive, measurable results. Do not get carried away with features. Center frequency 7.23MHz, bandwidth
0.3KHz and 0.5KHz/division. Search eham and qrz classified ads.

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1-4, INITIAL POWER UP
First and of critical importance, you must have a power supply that has been tested and meets all the original
specifications. NOTE: The actual B+, high voltage and negative bias voltages measured in your system will
vary from the values on the schematic and in this document. The AC input voltage must be from 105 to
125vac. A 5v change in the AC voltage will equate to about a 20vdc difference in the high voltage, 10vdc in the
B+ and about 5vdc change in the bias voltage. The voltages measurements in this document relate to 122vac
bench supply. You will need a dedicated voltmeter plugged into the test jacks in the rear of the PS-150 to
monitor plate current. It will remain there throughout all testing. It will need 2.5v full scale and 5 or 10v full
scale switch positions. Remove the top and bottom covers of the HT-44. Remove the case.
BE AWARE, from this moment on you are exposed to LETHAL HIGH VOLTAGE.
Unless otherwise noted the turn on preset conditions will be:
•VFO SELECTOR ------------------- XMTR
•MIC GAIN --------------------------- Ø
•RF LEVEL --------------------------- Ø
•FINAL TUNING -------------------- center of 40-meter bar.
•DRIVER TUNING ------------------ center of 40-meter bar.
•BAND SELECTOR ----------------- 7.0
•VFO DIAL --------------------------- 230
•FUNCTION -------------------------- AM
•OPERATION ------------------------ OFF
•DELAY ------------------------------- full counterclockwise
•CAL LEVEL ------------------------- full counterclockwise
•CAL RESET ------------------------- center of its rotation
•NORM/XCVE (slide switch on rear of chassis) ---- NORM
•ANTENNA -------------------------- connected to wattmeter/dummy load
NOTE: Throughout all testing when powered up, OPERATION in MOX position and FUNCTION in the AM
position is the “safe” mode. There should not be any plate current in the PA final tubes. Any time you are not
performing a specific test the equipment should be in the “safe” mode.
Before turn on:
Locate and become familiar with the following, R124, 5k 10w, pin 11 of S1 (VFO SELECTOR should be a
solid white wire). Remove the PA cover.
CAUTION YOU WILL BE EXPOSED TO LETHAL VOLTAGES.
OBSERVE THE FREE HAND RULE, THAT IS FREE HAND IN HIP
POCKET WHILE TAKING MEASUREMENTS. YOU COULD DIE.
NOTE: The PS-150 power supply voltages normally run much higher than original documents and schematics
indicate. I suspect this was true when the radios were new. A clue can be found on the voltage chart figure 12
in the original factory manual. You will note the screen voltage with the PA tubes cut-off was charted as
285vdc. That would have been with the AC input at 117vac. My bench power runs 123vac. The nominal
voltages for the PS-150-120 power supply on my bench are: The +250vdc runs +305vdc. The -125vdc runs -
150vdc. The +575vdc runs 680vdc. The +150vdc should be 150vdc +/- 2vdc. Throughout this document I will
use the values as documented in the original manual.

8
1-4-1, VOLTAGE VARIFICATION TESTS
We are now going to measure the B+ 250vdc, the regulated 150vdc, the High Voltage 575vdc and measure and
preset the bias voltage. This will be a no-load condition and the voltages will read 5 to 10% high.
Insure all the cable connections are correct. Turn the OPERATION SWITCH to MOX. There should be no
indication of plate current on the meter monitoring the power supply.
The end of R124 connected to the terminal strip should measure ≈+250vdc
The end of R124 connected to V11 pin 5 should measure 150vdc +/- 2.0vdc
The metal strip the tube plate parasitic suppressors connect to should measure ≈+575vdc
Tab 11 of S1 should read a negative voltage. Adjust R206 (BIAS ADJUST) on the rear of the power supply for
the maximum negative voltage it should read ≈-125vdc. We will leave it at the max setting for now. If these
voltages are ok power down. Replace the PA cover. Since you are using a known to be good power supply, the
absence of one of these 4 voltages would most likely indicate a wiring fault which needs to be cleared before
you can proceed.
1-4-2, INITIAL BIAS ADJUSTMENT
Insure all the controls and switches meet the turn on preset “safe” conditions. Turn the OPERATION switch
to MOX and allow 10 minutes for warm up.
Turn the FUNCTION switch to CW and adjust the BIAS ADJ on the power supply for 1v on the meter
connected to the power supply test jacks. One volt reflects 100ma of idle current. Return the FUNCTION
switch to AM and turn the OPERATION switch to OFF. If this procedure was successful you are ready to
proceed to the oscillator test procedures. If you are unable to set the idle current then the PA final tubes are bad
or the grid, screen or plate voltage is missing. See figure 12 in the factory manual for aid in isolating this fault.
1-5, OSCILLATORS
There are three oscillators in the system, the carrier oscillator, the heterodyne oscillator and the VFO. We will
address the carrier oscillator first.
1-5-1 CARRIER OSCILLATOR TEST AND VERIFICATION
The carrier oscillator is one half of V1
Power up in the “safe” mode. While waiting 10 minutes for warm-up locate the junction of R5 (56 ohm) and R6
(220 ohm). Connect the scope using a 10X probe to the junction of R5 and R6. When the unit has warmed up
move the FUNCTION switch to CW. You should see approximately 3vpp of 1650KHz on the scope. Adjust T1
for max signal. Move the probe from the scope to the frequency counter. Adjust C1 for exactly 1650KHz.
Return to AM mode. Move the probe back to the scope. Connect a microphone and key the mic, you should see
carrier on the scope when the mic is keyed. You should get the same results when you key the mic in USB
mode and LSB mode. Remove the microphone. Set the OPERATION switch to STBY rotate the FUNCTION
switch through all 4 modes, you should have carrier signal on all modes. The same will be true for CAL and
VOX. Return the controls to the “safe” mode. Plug the telegraph key into the key jack on the rear panel. Turn
the OPERATION switch to VOX and set the FUNCTION switch to CW. When you press the key, you should
see carrier on the scope. Rotate the DELAY control CCW press and release the key and note the fast dropout of
the carrier osc. Rotate the DELAY fully clockwise press and release the key note a delay in drop out of approx.
1 second. Return all controls to the “safe” mode.
This completes the carrier oscillator tests. You have now proven the operation of the carrier oscillator and most
of the function and operation switch functions.

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1-5-1-1, CARRIER OSCILLATOR FAULT ANALYSIS
If the equipment failed the tests in 1-5-1 the following measurements should aid in fault analysis.
Setup in “safe mode”.
You will be making measurements at the junction of R1 and R2, the bottom of R2, and V1 pin1, pin2 and pin3.
To get accurate measurements you must insure that your meter does not load the oscillator. Connect the scope
to the junction of R5 and R6 and observe the signal. Move the FUNCTION switch to CW. Now touch pins 1, 2,
and 3 with the meter probe while observing the signal on the scope. If the probe causes a significant change in
the amplitude of the signal you need a better meter.
MODE / VOLTAGE CHART
OPERATION
FUNCTION
R1 –R2
R2 bottom
V1pin1
V1 pin2
V1 pin3
MOX
AM
-138vdc
-140
265vdc
-130vdc
0.0vdc
MOX
CW
-1.4vdc
0.0vdc
199vdc
0.0
3.0vdc
NOTEs: Some schematics have R2 listed as C2. Voltages will differ from rig to rig. In the rig used for these readings the
250vdc measured 313vdc, the bias measured -140vdc.
1-5-2 HETRODYNE OSCILLATOR.
The Het Osc is comprised of V15 and its associated circuitry. V15A is the oscillator section and V15B is the cathode
follower/buffer. This oscillator is the most troublesome of the three. There are no adjustments to pull the frequency of
each xtal. So, if you do not have a box of spare xtals you are rather limited in what you can do to put it precisely on
frequency. First thing, check the oscillator output. Connect the scope to the tie point of C121 and L31 which are located
in the cathode ckt of V15B. The minimum peak to peak voltages for each band should be: 80 meters 3.75 Vpp, 40 meters
2.5 Vpp, 20 meters 2.5 Vpp, 15 meters 1.5 Vpp, 10 meters (all 4 segments) 1.5 Vpp.
If all the bands are off in one direction you can offset some of the error with the carrier oscillator. The
frequency synthesis is: TX frequency = (Het osc) –(carrier osc + VFO). If all the bands are high by say 500Hz
then adjust the carrier osc to 1650.5KHz and you are good to go.
HET OSC VOLTAGE CHART
FUNCTION
OPERATION
V15
PIN 1
PIN 2
PIN 3
PIN 6
PIN 7
PIN 8
MOX
AM
144
0
0
302
57
53
1-5-3 VFO
The VFO is comprised of V10 A & B and associated circuitry. If it has stability problems most likely the fault is
C27, 15pf N220 and C28, 51pf N80 the temperature compensating capacitors. V10A is the oscillator section
and V10B is the buffer, cathode follower. This is an extremely stable oscillator design, if it drifts it has a fault.
Find the failed component and replace it. Do not try to “modify stability into it”.

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1-5-3-1 VFO TEST AND ALIGNMENT
SETUP:
Connect frequency counter to the switch side of C17 using a 10x scope probe. Preset C29 to the center of its
tuning range. Adjust the CAL RESET to center of its rotation.
Turn the OPERATION switch to MOX.
Turn the FUNCTION switch to AM mode.
Allow 30 minutes warm-up/stabilize time.
INITIAL PRESET.
Tune the main tuning dial to 300.
Adjust L4 for a reading of 4.550MHz on the frequency counter.
FINAL TRACKING ALIGNMENT.
Tune the main tuning to 100 and adjust C29 for 4.750MHz on the counter.
Tune the main tuning to 400 and adjust L4 for 4.450MHz on the counter.
NOTE: These two adjustments interact, you may have to go back and forth, under or over correction at
one or the other end to get both ends correct.
FINAL TRACKING CHECK
MAIN TUNING FREQUENCY
00 4.850MHz
100 4.750MHz
200 4.650MHz
300 4.550MHz
400 4.450MHz
500 4.350MHz
Move the scope probe from the frequency counter to the scope
Set the main tuning to 250.
Adjust L2 for max signal. This signal should exceed 0.500 vpp.
Turn main tuning from 250 to 500 then to 0. The signal should not drop more than 0.075 volts at either end.
This completes the VFO tests and adjustments.
VFO VOLTAGE CHART
OPERATION
FUNCTION
V10
PIN 1
PIN 2
PIN 3
PIN 6
PIN 7
PIN 8
PIN 9
MOX
AM
141vdc
0
86
141*
0
4
0
*Measured at junction of L2 & R24

11
1-6, DRIVER/PA PRETEST & SETUP
In order to properly test and analyze the audio, phasing and I.F. circuits properly the driver and PA need to be at
or near normal. The 6DQ5 final tubes must be a matched pair. If you are unsure of the conditions of the final
tubes proceed to section 3-1, ERRATA SHEET TUBE MATCHING and follow the instructions.
1-6-1, DRIVER & PA PRESET
Read through the following procedure to insure you understand all of the instructions before you start
the operations.
Set the switches and controls to the “SAFE” configuration. Attach a microphone. Set the band switch to 40-
meter band. Insure MIC GAIN and RF LEVEL are set to zero. Set the signal generator to 7.23 MHz and max
signal out. (output must be greater than 100,000uv). Using the 1X probe inject the signal from the generator into
pin 2 of V8 (SECOND MIXER). Insure the test meter is connected to the test jacks in the rear of the power
supply. Preset the DRIVER TUNE and the FINAL TUNE for the center of the 40m bar.
Connect wattmeter and dummy load to transmitter output.
•Watching the plate current on the test meter and the power out on the wattmeter key the mic.
•Throughout this process do not key the mic for more than 3 to 4 seconds at a time
•If you have power out adjust the drive from the signal generator for 35 to 50 watts. Keep adjusting the
generator to maintain the output at 35-50 watts throughout this process.
•If there is low or no power out observe the plate current and adjust the DRIVER TUNE for a plate
current peak.
•Once the driver is peaked adjust the FINAL TUNE for a dip in plate current.
•Adjust L8 and L18 for max power out.
If you are unable to get a minimum of 35 watts out then you have a fault in V8, 9, 16 or 17, or their associated
circuitry. See section 2-2-4 DRIVER/PA TROUBLESHOOTING. This fault must be cleared before proceeding
see section 2-2-4.
1-6-2, 6.5 MHZ TRAP
NOTE: This is the final adjustment for the 6.5meg trap.
Set the signal generator to 7.00 MHz. Set the RF LEVEL to zero, MIC GAIN to zero. Key the mic and adjust
the DRIVER TUNE and the FINAL TUNE for max power at 7.00 MHz:
•Readjust the generator for 6.25MHz.
•DO NOT readjust the LEVEL or GAIN.
•Key the mic and adjust L11 (6.5MHz TRAP) for MINIMUM power out.
If you cannot null the 6.5MHz then either L11 or C59 is at fault. This completes the driver/PA pretest and setup.

12
1-7 FIRST MIXER, 6-6.5MHz I.F., SECOND MIXER
The first mixer, 6meg IF and second mixer train is composed of V6, T3, V7A, T4 and V8.
1-7-1, MIXER/I.F. SETUP & ALIGNMENT
Power up in safe mode. Allow 10 minute warm up.
Locate test points TP 1, TP 2 and TP3.
1-7-1-1, INJECTION LEVEL PRETEST
Set RF LEVEL to max.
Connect microphone.
Band switch to 7.0.
Connect the scope to TP1 pin 1 of V6. Key the mic and you should see 0.5vpp (from the carrier oscillator). If
not Adjust T2 for 0.5vpp.
Connect the scope to TP2 pin 7 of V6. You should have 0.5vpp constant. (from the VFO). If this signal is not
present there is a fault in S1 (VFO SELECTOR) or you made an error in the 1-5-3 section tests. Return there
and correct the fault.
1-7-1-2, 6MEG ALIGNMENT
Connect the scope to TP3 pin 2 of V8. Set the VFO to 100 and adjust T3 and T4 top ends for max signal on the
scope (approx. 1vpp). Tune the VFO to 400 and adjust T3 and T4 bottom ends for 1vpp signal.
Recheck at 100 and 400 on the dial and retune until both ends are the same you should have 1vpp +/- 0.3vpp.
MIXER/IF VOLTAGE CHART
V6
V7
V8
PIN
VOLTAGE
PIN
VOLTAGE
PIN
VOLTAGE
1
0
2
0
2
-144/-0.5
2
1.0 *
3
83/73
7
317/276
5
317/277
6
1.1/0.9
8
158/57
6
61/53 *
7
317/274
7
0
Voltages with * will differ dependent upon band selection.
Measured in MOX, AM, RF LEVEL at max. first voltage unkeyed/second voltage keyed.

13
1-8 DRIVER / PA ALIGNMENT
The driver/pa alignment can be done in either CW mode with telegraph key plugged in or AM mode with mic
attached and with the MIC GAIN set to zero. CW is preferred.
Throughout the driver / pa alignment you will need to constantly adjust the RF LEVEL to stay at 100 watts.
Keep backing down on the RF LEVEL to insure you are seeing the true coil peaks. You may have to adjust T2
if you cannot get 100 watts.
Set up the controls to the “safe” configuration.
1-8-1, DRIVER/PA COIL ADJUSTMENTS
On each of the following bands preset the driver and final tuning controls to the center of their respective band
segment markings (see figure below). Then tune the coils to these mechanical positions. If they will not tune up
with the controls located as indicated on the front panel proceed to section 2 SUBSYSTEM TROUBLE
SHOOTING, 2-2-6, DRIVER TUNING SETPOINTS.Return to this point when fault is cleared.

14
1-8-2, 10 METER ADJUSTMENT
Set the band switch to 28.5 tune the VFO to 750. Set the DRIVER TUNING per the photo above. Preset the
FINAL TUNING in the same manner as you did the DRIVER TUNING. Key the transmitter and advance the
RF LEVEL until you start to see a rise in plate current (on the meter attached to power supply monitor jacks).
Adjust L5 and L15 for max plate current. Tune the FINAL TUNING for max power and observe the plate
current. A plate current dip should occur in coincidence with, or very close to the power output peak. Double
check the peak points on each coil and controls several times until there is no improvement
If you are unsuccessful getting proper power output proceed to 2-2-4 DRIVER/PA TROUBLESHOOTING.
When you have corrected the fault return to this point.
1-8-3, 15 METER ADJUSTMENT
Set the band switch to 21. Set the VFO to 360 Set the DRIVER TUNING per the photo. Repeat the process
used in 1-8-2 adjusting L6 and L16
1-8-4, 20 METER ADJUSTMENT
Set the band switch to 14. Set the VFO to 280 Set the DRIVER TUNING per the photo. Repeat the process
used in 1-8-2 adjusting L7 and L17
1-8-5, 40 METER ADJUSTMENT
Set the band switch to 7. Set the VFO to 230 Set the DRIVER TUNING per the photo. Repeat the process used
in 1-8-2 adjusting L8 and L18
1-8-6, 80 METER ADJUSTMENT
Set the band switch to 3.5. Set the VFO to 900 Set the DRIVER TUNING per the photo. Repeat the process
used in 1-8-2 adjusting L9 and L19
1-9, PA NEUTRALIZATION
Neutralization is the process of nullifying the effect of direct grid to plate coupling of energy via the
interelectrode capacitance between the plate and the grid. This process removes the DC drive and eliminates
any gain factor in the PA. With PA gain eliminated any energy measured on the plate is a result of the plate to
grid capacitive coupling. Our goal is to minimize this energy. It is correct when the PA power out peak and the
PA plate current dip coincide.

15
1-9-1, NEUTRALIZATION PRE-TUNE
Power up in the safe mode. Set the band switch to 21. Set the VFO dial to 360. Set the RF LEVEL to 8. Switch
to CW and adjust the DRIVER TUNE and FINAL TUNE for max power out. Reduce the RF LEVEL as needed
to keep the power out at 45 - 65 watts. (you may have to peak L6 and L16 to get power peak.) Once you have
tuned up you will not readjust the DRIVER TUNE or the FINAL TUNE throughout the rest of the
neutralization process.
1-9-2, NEUT. SET UP
Power down the transmitter.
•Remove PA cover.
•Locate the wire connected to the base of the plate choke L27 and disconnect
it. Tape the end of the wire or otherwise protect it from touching anything.
•Locate R77,1.8K 1w resistor. Disconnect it at the terminal strip end.
Power up in safe mode and insure the RF LEVEL is at minimum. Allow enough warm up time to insure the PA
tubes are up to max temp. Connect the scope to ungrounded end of L29. Switch to CW and advance the RF
LEVEL until you get good signal on the scope. Adjust C77 for minimum signal. Some advance of the RF
LEVEL and the scope gain will be needed as you approach the null.
This completes the neutralization process.
1-10, CARRIER DRIVE LEVEL
The carrier oscillator ckts have enough drive to drive the transmitter to well over 200 watts. However, the audio
phasing and modulation ckts are only designed to operate efficiently at the 100 to 130-watt level. It is critical
that T2 be set to the proper level. Select the center of any band.
1-10-1 CARRIER LEVEL ADJUSTMENT
Set the transmitter to the “save” mode allow 10 minutes warm up. KEEP THE TRANSMITT TIME TO A
MINIMUM. It is recommended to plug in a telegraph key and only go key down in short bursts while making
the adjustment. This also saves wear and tear on the function switch.
•Set the RF LEVEL to 8.
•Key the transmitter and tune the DRIVER TUNING and the FINAL TUNING max power.
•Unkey and rest the finals for a few seconds.
•Key the transmitter and tune T2 for 130 watts output.
•Unkey and rest the finals for at least 20 seconds.
•Key the transmitter and check power out make readjustment of DRIVER TUNING and FINAL
TUNING. If the power out exceeds 130 watts back it off with a detune of T2.
•Key check power, unkey and rest several times to insure stability of adjustment.
NOTE: At this point, if you have followed the process as written all the major systems have been tested
and proven. You are about to start the modulation and carrier suppression test and evaluation. There are
components that have not been tested at this point. They are: V4, T7, and some switching functions of the
FUNCTION and OPERATION switches. If you are not able to generate SSB power in the section 1-11
check V4, T7 and the switches. So far, we have worked around the VOX, ANTI-TRIP and AALC
functions. Tests and adjustments of these subsystems are covered in section 2.

16
1-11, MODULATION AND CARRIER SUPPRESSION
If you do not have a spectrum analyzer perform the tests and adjustments described in the factory manual.
These will be found in section 9-11, paragraphs 1 through 23.
If at all possible, buy, beg or borrow a spectrum analyzer.
One day about 40 years ago while working on a Collins ARC/38A, I wanted to look at the spectrum on SSB and
also monitor the mod envelope in AM. I had old roller coil, 2” in diameter with 20 turns. I attach coax, BNC, T
connector and attached to both the spectrum analyzer and the scope. I place the coil as close as I could to the PA
assembly. Sometimes it is a little crude but it works fine to this day.
I can make AM observations switch to SSB or CW and make spectrum observations. Simple speedy.

17
1-11-1 CARRIER SUPPRESSION TEST AND ADJUSTMENT
Set up the 44 in the safe mode, power up and allow 15 minutes for warm up. The warm up is important, you
must insure all components are up to operating temperature.
Tune for max power in the center of any band in CW or AM.
•Connect mic patch cable, adjust audio oscillator for 5mv, 1000Hz.
•Set MIC GAIN to 8.
•Set function to LSB
•Set spectrum analyzer center freq to 7.23 MHz.
•Key the transmitter and adjust the CARRIER BAL controls R8 and R13 for minimum carrier signal.
•Unkey, switch to USB
•Key up, check carrier suppression adjusting R8 and R13 to test for min carrier.
•Go back and fourth from USB and LSB to insure carrier suppression is equal.
•Return equipment to “safe” mode.

18
1-11-2 UNWANTED SIDEBAND REJECTION
Set up the 44 in the safe mode, power up and allow 15 minutes for warm up. The warm up is important, you
must insure all components are up to operating temperature.
Tune for max power in the center of any band in CW or AM.
1. Connect mic patch cable, adjust for 5mv, 1000Hz.
2. Set MIC GAIN to 8.
3. Set function to LSB
4. Set spectrum analyzer center freq to 7.23MHz.
5. Key the transmitter
6. Adjust the AUDIO Ø BAL and the AUDIO BAL controls for minimum USB signal.
7. Unkey, switch to USB
8. Key up, check LSB signal suppression, adjusting AUDIO Ø BAL and the AUDIO BAL controls for
minimum. A slight tradeoff between USB and LSB may be required. But if the minimum setting for one
or the other causes difference of more than 5db a fault has occurred. That fault is most likely a tube
failure.
9. Return equipment to “safe” mode.
•Repeat steps 1-5 adjusting RFØL and RFØC for max rejection of unwanted sideband.
Once again, a slight tradeoff between USB and LSB may be required. But if the minimum setting for one or the
other causes difference of more than 5db a fault has occurred. That fault is most likely a tube failure.
This completes the test and adjustments. Go to section 2-2-7, GOING ON THE AIR WITH THE 44.

19
2 SUBSYSTEM ADJUSTMENT & TROUBLE SHOOTING
2-1 MICROPHONE AUDIO
2-1-1, VOLTAGE CHART
NOTE: On the unit under test the +250-volt buss actually measured 315vdc. It is not uncommon for the 250vdc buss to
run from 300 to 330vdc with AC line voltages between 120 and 124vac.
V2
V1B
V5
1
57v/(50v STBY)
5
260v/(227 AM KEYED)
1
260V/(227 AM KEYED)
2
0.0
7
0.0
2
0.0
3
0.34
8
2.6v/(3.0v STBY)
3
2.0
6
60v/ (160 STBY)
/
////////////////////////////////////////////
6
260/(227 AM KEYED)
7
-0.7v/(140v CW)
/
////////////////////////////////////////////
7
0.0
/
///////////////////////////////////////////
/
////////////////////////////////////////////
8
2.0
2-1-2, SIGNAL LEVEL CHART
Inject 12mvpp, 1000Hz @ test point A.
Measurement taken in MOX, AM, mic keyed, MIC GAIN adjust for 90 to 95% modulation.
B
C
D
E
F
0.012vpp
0.39vpp
3.9vpp
1.0vpp
1.0vpp
2-1-3, REFERANCE VOLTAGES
Test point G
Test point H
0.0/(-130 CW)
260vdc

20
2-2, VOX TEST AND TROUBLESHOOTING
Relay K1 provides the internal switching for the transmitter. Tube V13B is the control element for K1. V13B
gets its turn on command from the PTT line or the VOX subsystem. When in the VOX mode a sample of the
first mic amp (V2) output is fed to the VOX circuit (V12A and V13A). The VOX circuit sniffs this signal
rectifies it to create a DC voltage relative to the mic input signal. A voltage divider in the cathode of V14C
which is connected to the grid of V13B sets up the quiescent off state for V123B. The DELAY control R90 sets
this quiescent state and the delay in cutoff when mic audio is no longer present. This quiescent state can be
triggered by rise in voltage on the grid of V13B or a lowering of the voltage on the cathode.
•In the VOX mode the mic signal amplified by V12A and V13A and rectified by V14C drives the grid of
V13B into the on state thus energizing K1.
•The vox drop out delay is controlled by time constant of C112, R90, R89, R88 and the function and
operation switches.
•When the OPERATON switch is in the MOX position S4A REAR pin 7 grounds any signal from the
vox amp preventing the vox from controlling relay K1.
•In the CW function all the timing resistors are in the circuit providing the longest drop out time.
•When the FUNCTION switch is in AM, USB or LSB switch S3A REAR pin 9 places a gnd at the
junction of R88 and R89 thus reducing the DELAY time constant for the voice modes.
•When the operation switch is in the MOX POSITION the PTT line is routed to the cathode of V13B.
When the PTT line is grounded the reverse bias on the cathode is removed and V13B turns on.