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Hallicrafters HT-44 Operation And Maintenance Manual Download Page 16

 

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. 
 

 

Summary of Contents for HT-44

Page 1: ...1 SUPPLEMENT TO OPERATION AND MAINTENANCE MANUAL HALLICRAFTERS HT 44 WDØGOF 02 28 2019 ...

Page 2: ...ment 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 http...

Page 3: ...CILLATOR 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 VOLT...

Page 4: ... 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...

Page 5: ... 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 ...

Page 6: ...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 mo...

Page 7: ...kwise 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...

Page 8: ...e 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...

Page 9: ...his 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 ...

Page 10: ...0 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 0 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 Adjus...

Page 11: ...rent 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 ...

Page 12: ...ignal 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 ret...

Page 13: ...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 locate...

Page 14: ...t 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...

Page 15: ...n 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 Th...

Page 16: ...out 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 ...

Page 17: ... 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 ca...

Page 18: ...SB 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 unwan...

Page 19: ...ween 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 VOLTA...

Page 20: ...rid 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 th...

Page 21: ...l in the center third of its rotation is normal 2 Control in the lower third of rotation indicates component drift or gassy tube in the VOX train 3 Control in the upper third of rotation indicates component drift or weak tube in the VOX train Leave all controls on the HT 44 as they are for the next series of tests If the VOX fails to operate properly there is a fault in the vox train Insure the co...

Page 22: ...the tests can be run without keying up the transmitter Dynamic test Connect the audio oscillator and the scope to high side of R103 ANTI TRIP Connect the DVM to pin 1 of V14 Adjust the audio oscillator output to 1400HZ and 3vpp as measured on the scope You should hear the tone in the speaker in the power supply Rotate R103 from end to end monitoring the voltage on pin 1 of V14 At the counter clock...

Page 23: ...L to minimum Remove the Het osc tube V15 Inject 7 23 MHz from signal generator into the tie point of C35 and L10 Place the tube pick up on V6 and connect the scope to it With mic installed key transmitter and increase drive from generator to produce 0 5vpp on the scope If you cannot get 0 5vpp on V6 then the mixer stage has a fault This fault must be cleared before you can proceed Move the tube pi...

Page 24: ...stments Read through the process before you start NOTE This same error will occur with the FINAL TUNING control It is usually caused when L28 has been deformed by high VSWR heating Getting the tuning back to where it should be usually requires a new L28 and optimizing C100 101 102 103 and 104 We will start with the 40 meter band Band switch to 7 0 VFO to 230 DRIVER TUNING to center of 40 tab In CW...

Page 25: ...onitor meter Adjust the BIAS ADJUST for 100ma of plate current Return to the safe mode 2 2 7 2 PA OUTPUT FINAL ADJUSTMENT As stated before the HT 44 is capable of much more than 130 watts output However the audio circuits were not designed to drive the system at higher power levels Set up and turn on the 44 in the safe mode Allow at least 15 minutes for everything to come up to temperature Tune up...

Page 26: ...26 3 ATTACHMENTS 3 1 ERRATA SHEET TUBE MATCHING ...

Page 27: ...27 3 2 INTERNAL R T RELAY MOD ...

Page 28: ...227 AM KEYED 1 260v 227 AM KEYED 2 0 0 7 0 0 2 0 0 3 0 34V 8 2 6V 3 0V STBY 3 2 0 6 60v 160 STBY 6 260v 227 AM KEYED 7 0 7V 140V cw 7 0 0 8 2 0 SIGNAL LEVEL CHART Measurement taken in MOX AM mic keyed MIC GAIN max Inject 12mvpp 1000Hz test point A B C D E F G H Test point I Test point J ...

Page 29: ... cleared 3 3 3 CARRIER OSC 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 3 3 4 HET OSC HET OSC VOLTAGE CHART FUNCTION OPERAT...

Page 30: ...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 First voltage unkeyed second voltage keyed 3 4 MISC 3 4 1 ANALYZER SCOPE PICKUP ...

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