I have a 5237 and it has aligned 6 receivers so far after a thorough going through. I also used a frequency counter to help align the unit. Its a regular piece of equipment on the bench now. Thanks for the video.
The biggest problem with restoring any Heathkit piece is that one is at the mercy of the builder! I have an IG-5237 that I am working on. Judging by the replacement knobs, it has been through at least two prior owners. I replaced all the electrolytic capacitors. The other capacitors and the resistors were within spec. The filament transformer lead was broken off from pin 5 of V5. I repaired that and fired the unit up. Alignment was going fine using a VTVM and oscilloscope until I got to the pilot level adjustment. I was missing the 1000 Hz signal coming from the cathode follower. And I only had half of the filaments lighting on V5. It turns out that pins 5 and 6 are broken off the at tube socket. I am presently waiting for snail mail to deliver some new sockets.
Nice video! It would be nice to see a video on the actual alignment procedure. I had trouble aligning mine. A previous owner permanently installed the precision resistors with a switch to switch them in and out for calibration. I have a funny feeling I may have forgotten switch it back to the operational position when I reached the 38khz alignment section. I'll have to go back and check!
Jeff, seems you are one of the only subject matter experts on this unit. I recently acquired a nice 5237. My primary question is what is this RF connector both of these units use. I cannot find a termination anywhere. I'm not sure what its called besides twin lead 300 ohm connector. Please provide some insight on this termination. Thanks Ben.
The connector is normally used for crystals, type FT-243 I think. I don't know why they used it in this case. You should be able to rig up something using some pins taken from an octal vacuum tube and soldering them to some 300 Ohm twin lead cable.
I thought I had seen on the internet some solid state versions of the 5237....I am waiting for the 5237 to arrive in the mail next week...so it will be interesting in seeing what I got! ~Jack, VEG
I purchased a IG-37 on eBay and just completed the alignment per the manual. I have built many Heathkits over the years and I to found this the most challenging to align. I am attempting to align a Heathkit AJ-30 fm tuner but having very little luck. I can not find the 10.7 signal on the IF marker out on the front panel. My scope shows a 5.35 frequency there and I see no harmonics described by the manual. Can anyone help here as the in-37 manual is very lacking of info on the IF procedure. I have checked v5 wiring changed out V1 with V5 and checked the function switch wiring per troubleshooting in manual with no luck. Thanks john
Terrific video! Thanks for posting. I just picked up an IG-37 and would like to run through the generator alignment procedure. My unit came without the precision resistor also. Can you elaborate on what you did to get through the "Audio Oscillator Calibration" without having the precision resistors? What position are the "Function" and "Frequency" switches supposed to be in for the Audio Oscillator Calibration test? Thanks for your consideration.
I used standard resistors with similar values for the precision ones: 4.7K for 4590 and 15K for 13.5K and followed the instructions in the manual.What this does it make the audio oscillator run at 19 kHz, the same as the separate 19 kHz oscillator, and you adjust them to be the same. If you have a frequency counter or calibrated oscillosocpe, a better procedure seems to be not to use the resistors, and adjust the 38 KHz oscillator to free run close to 38 kHz. Then in the later step where the 19 and 38 kHz should be synchronized in phase, they should be.
Thanks again for your insight on how to calibrate the audio oscillator section. Just as a follow up here’s how I finally calibrated the circuit. I used two miniature 10-turn pots as substitutes for the 4590 Ω and 13.5 KΩ resistors and twiddled them until they were dead on. Using two channels on my oscilloscope I placed one probe on TP1 and the other on the “Composite Sig Audio” connector. Triggering from TP1 it was a surprisingly easy to adjust the frequency trimmer until both 19 kHz waveforms were locked in phase and frequency. The Heathkit IG-37 is certainly a peculiar unit to calibrate. After getting screwy results following Heath’s “Balanced Modulator Adjustment” instructions here’s what I did calibrate that section. Using two channels on my oscilloscope I placed one probe on T2 pin 4 (location where C28 and D3 connect). Then I placed a second probe on T3 pin 3 (location where C29 and D2 connect). I left V1 (12AU7) tube in circuit and set R54 (Balance Mod Control) to midpoint. I adjusted T2 and T3 until both scope channel waveforms were identical in shape and amplitude. Finally, at the end I measured the voltage at the “Composite Sig Audio” connector with V1 (12AU7) out following Heath’s instructions. I measured .03V rms, the instructions called for a range of .01 to .05 volts rms. One other note worth mentioning. After I replaced the main 3-section electrolytic I still noticed a lot of ripple. I added an extra 150 uF at the cathode of diode D1 in the power supply section. It knocked the AC ripple down by about 50% more than typical.
Does anyone know what the expected left/right channel separation is on the IG37 in the stereo test modes? I do not see this specification anywhere and I am only getting a few dB which I suspect is too low.
mikgus - Yes. I also could not meassure the 5 kHz Signal before but I found a Way to check it. I recorded the Tones in Audacity and used the Frequency Analysis of Audacity to check the Frequencies. :D The Results were very close to Your Results. I got 436 Hz, 1070 Hz and the 5 kHz Signal (which I also could not check before) seems to be almost Spot on.. 4,999 kHz... :) But I also found out, that for the Alignment of the Audio Frequencies two additional special Precision Resistors are needed, the Ones that were mentioned in the Video. Without them it must be difficult to align all Audio Frequencies properly.. I guess.. :/
Yes, the 400 Hz measures about 437 Hz and 1000 at 1060 Hz. There is only one frequency adjustment that affects all ranges, and it is more important that it be close at 19 kHz and 38 kHz. There is no published spec on how close the audio frequencies should be, but it doesn't really affect the operation.
This is why a subscribe to this channel. I find this generation of electronic interesting but don't have the time and knowledge to do it myself. i got the frequencies by holding my phone with a guitar-tuner app infront of the computer speaker.
Great video. This should be a template for tech videos on UA-cam. No stupid background music, no waffling about unrelated stuff. Just the facts
I have a 5237 and it has aligned 6 receivers so far after a thorough going through. I also used a frequency counter to help align the unit. Its a regular piece of equipment on the bench now. Thanks for the video.
Thanks for this. Just got one of these myself, and appreciate the information you provide.
I also want to thank you for this useful video! I'm thinking about purchasing one, that's how i found your well made presentation.
The biggest problem with restoring any Heathkit piece is that one is at the mercy of the builder! I have an IG-5237 that I am working on. Judging by the replacement knobs, it has been through at least two prior owners. I replaced all the electrolytic capacitors. The other capacitors and the resistors were within spec. The filament transformer lead was broken off from pin 5 of V5. I repaired that and fired the unit up. Alignment was going fine using a VTVM and oscilloscope until I got to the pilot level adjustment. I was missing the 1000 Hz signal coming from the cathode follower. And I only had half of the filaments lighting on V5. It turns out that pins 5 and 6 are broken off the at tube socket. I am presently waiting for snail mail to deliver some new sockets.
Nice video! It would be nice to see a video on the actual alignment procedure. I had trouble aligning mine. A previous owner permanently installed the precision resistors with a switch to switch them in and out for calibration. I have a funny feeling I may have forgotten switch it back to the operational position when I reached the 38khz alignment section. I'll have to go back and check!
Wonderful job
I have one of these. Still on my bench, but rarely used.
Jeff, seems you are one of the only subject matter experts on this unit. I recently acquired a nice 5237. My primary question is what is this RF connector both of these units use. I cannot find a termination anywhere. I'm not sure what its called besides twin lead 300 ohm connector. Please provide some insight on this termination. Thanks Ben.
The connector is normally used for crystals, type FT-243 I think. I don't know why they used it in this case. You should be able to rig up something using some pins taken from an octal vacuum tube and soldering them to some 300 Ohm twin lead cable.
I thought I had seen on the internet some solid state versions of the 5237....I am waiting for the 5237 to arrive in the mail next week...so it will be interesting in seeing what I got! ~Jack, VEG
Thanks for this video i love heathkit
I purchased a IG-37 on eBay and just completed the alignment per the manual. I have built many Heathkits over the years and I to found this the most challenging to align. I am attempting to align a Heathkit AJ-30 fm tuner but having very little luck. I can not find the 10.7 signal on the IF marker out on the front panel. My scope shows a 5.35 frequency there and I see no harmonics described by the manual. Can anyone help here as the in-37 manual is very lacking of info on the IF procedure. I have checked v5 wiring changed out V1 with V5 and checked the function switch wiring per troubleshooting in manual with no luck.
Thanks john
Thank you!
Terrific video! Thanks for posting. I just picked up an IG-37 and would like to run through the generator alignment procedure. My unit came without the precision resistor also. Can you elaborate on what you did to get through the "Audio Oscillator Calibration" without having the precision resistors? What position are the "Function" and "Frequency" switches supposed to be in for the Audio Oscillator Calibration test? Thanks for your consideration.
I used standard resistors with similar values for the precision ones: 4.7K for 4590 and 15K for 13.5K and followed the instructions in the manual.What this does it make the audio oscillator run at 19 kHz, the same as the separate 19 kHz oscillator, and you adjust them to be the same. If you have a frequency counter or calibrated oscillosocpe, a better procedure seems to be not to use the resistors, and adjust the 38 KHz oscillator to free run close to 38 kHz. Then in the later step where the 19 and 38 kHz should be synchronized in phase, they should be.
Thanks again for your insight on how to calibrate the audio oscillator section. Just as a follow up here’s how I finally calibrated the circuit. I used two miniature 10-turn pots as substitutes for the 4590 Ω and 13.5 KΩ resistors and twiddled them until they were dead on. Using two channels on my oscilloscope I placed one probe on TP1 and the other on the “Composite Sig Audio” connector. Triggering from TP1 it was a surprisingly easy to adjust the frequency trimmer until both 19 kHz waveforms were locked in phase and frequency.
The Heathkit IG-37 is certainly a peculiar unit to calibrate. After getting screwy results following Heath’s “Balanced Modulator Adjustment” instructions here’s what I did calibrate that section. Using two channels on my oscilloscope I placed one probe on T2 pin 4 (location where C28 and D3 connect). Then I placed a second probe on T3 pin 3 (location where C29 and D2 connect). I left V1 (12AU7) tube in circuit and set R54 (Balance Mod Control) to midpoint. I adjusted T2 and T3 until both scope channel waveforms were identical in shape and amplitude. Finally, at the end I measured the voltage at the “Composite Sig Audio” connector with V1 (12AU7) out following Heath’s instructions. I measured .03V rms, the instructions called for a range of .01 to .05 volts rms.
One other note worth mentioning. After I replaced the main 3-section electrolytic I still noticed a lot of ripple. I added an extra 150 uF at the cathode of diode D1 in the power supply section. It knocked the AC ripple down by about 50% more than typical.
Does anyone know what the expected left/right channel separation is on the IG37 in the stereo test modes? I do not see this specification anywhere and I am only getting a few dB which I suspect is too low.
Wowwww this is
cool
Also the IG-112
before the lid was lifted I thought it was all solidstate.. nope!
Yup...REAL stereo generators glow in the dark ;-)
Interesting. In this Video the Audio Frequencies are a bit "high", I think. 400 Hz sounds almost like 440 Hz. Would this be within Tolerance or not?
435,5
1069,8
couldn't mesaure the 5KHz signal
mikgus - Yes. I also could not meassure the 5 kHz Signal before but I found a Way to check it. I recorded the Tones in Audacity and used the Frequency Analysis of Audacity to check the Frequencies. :D
The Results were very close to Your Results.
I got 436 Hz,
1070 Hz and the
5 kHz Signal (which I also could not check before) seems to be almost Spot on.. 4,999 kHz... :)
But I also found out, that for the Alignment of the Audio Frequencies two additional special Precision Resistors are needed, the Ones that were mentioned in the Video. Without them it must be difficult to align all Audio Frequencies properly.. I guess.. :/
Yes, the 400 Hz measures about 437 Hz and 1000 at 1060 Hz. There is only one frequency adjustment that affects all ranges, and it is more important that it be close at 19 kHz and 38 kHz. There is no published spec on how close the audio frequencies should be, but it doesn't really affect the operation.
This is why a subscribe to this channel. I find this generation of electronic interesting but don't have the time and knowledge to do it myself. i got the frequencies by holding my phone with a guitar-tuner app infront of the computer speaker.
Thanks for the Answer! Yes, those Frequencies are the most important!