Fixing old radios, at 01:30 in the morning
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!!
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!!
