Fixing old radios, at 01:30 in the morning

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67Dart273

67Dart273

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Hammarlund HQ-129X, someone had tried to replace all the caps and did a slop job, and it did not work. I resorted to measuring voltages at the tube sockets, and about the 2nd IF amp had no plate voltage. So I shut it down and dug around, and the wire from the plate into the adjacent IF transformer was broke and "accidently" got tucked away behind a terminal strip where it was not noticable. So after reconnecting that wire, now the radio receives kinda, but you cannot copy CW (Morse) or SSB. The BFO switch when activated, kills all audio, WTF?? The BFO oscillator tube is in this VERY annoying shield can, so you're reaching in there with long needle nose. The coupling cap for the BFO output was leaking DC (hi voltage) into the detector, and blocking the audio. You can burn stuff up that way. This is a tiny cap, 5 picofarads. I do not have any, nor do I have say, some 10's that I could wire two in series to make 5. But I DID find this little trimmer cap (the white thing) out of a piece of German Siemans telco test gear I junked. In it went with new screen and plate bypass caps and here we FREEKING are, at 1 damn 30 in the morning!!! And, it WORKS!!

BFO.JPG


oldcaps.JPG
 
This ain't mine, a photo stolen off the internet. HF receiver, broadcast band up through 30 Mhz

HQ129pts.jpg
 
So did you replace the rest of the caps or just those two paper ones and that mica?

Glad you got it working, looks like back in the day that would have been a nice set.
 
Love to see guys on the forum that are also into tube electronics. I build audio amps in my basement and I guess this sort of has some connection to the whole car thing
 
mopardude62 said:
So did you replace the rest of the caps or just those two paper ones and that mica?

Glad you got it working, looks like back in the day that would have been a nice set.
Click to expand...
The first sentence. Someone got there before me but did a sloppy job. The "orange drops" you see on the edges of the photos are what someone else did. I'm sure that's why the feed to the IF transformer was broken, and whoever the "tech" was wasn't smart enough to find it. And look at the two paper ones + the mica out of the BFO can Evidently was not smart enough to look in there, either LOL

This old girl is not in the greatest of shape, but at least it's not very rusty or corroded.
 
Del, I admire your intellect and tenacity but 1:30 am is just to dang late to be staying up til.
 
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