#1
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Zenith J733 AM/FM Clock Radio Issues
Hello everyone, I had picked up from my local Goodwill a few years ago a 1952 Zenith J733 AM/FM Clock Radio that when I first got it the radio still worked flawlessly on the original parts including filter caps, but the a couple months later the filter caps finally started failing so I just went in and completely recapped the radio and it had been working fine since.
Well fast-forward about 7 years and the radio is doing some weird things like on the AM band its making noises similar to what you would hear on a radio that has Silver Mica Disease, but that's not what it is, because the IF cans in this radio aren't the correct type of IF cans to be giving those types of issues, and then the FM Band is completely dead. I've tried swapping out the two 6BJ6 tubes, the 12AT7 tube (which is the oscillator tube, which when I tested it on my newly acquired Knight Model 600 Tube Checker, it tests marginal) and I've even replaced the 12BA6 tube in the radio and I've tested the rest of the tubes in the radio and they test fine, and it still is doing that weird thing I've described in the previous sentence. I've installed a NOS 12BA6, and no change, I've installed a NOS 6BA6 in place of one of the 6BJ6s and no change (actually the radio is just dead silent except for a little hiss on both bands) I've installed a lightly used 12AU7 tube in place of the 12AT7 and the radio is now acting like A signal generator and sending out a signal to my old Sankyo AM/FM Clock Radio at around 1000 kC, which is weird because it never did that before. Is this radio's RF and IF circuitry so sensitive that it needs to have exact tubes in it and that it can't have substitutes installed, or it will wig out? Any help would be appreciated. |
#2
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Never mind I figured it out, it was a combination of a sticky/dirty band switch and a couple of noisy tubes, its working fine now!
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