02-02-2006, 05:00 PM
Scott:
Chuck will have the most knowledge here, but I'll try to help if I can. Forgive me if my questions make you repeat yourself, but it might be the best way to proceed.
Was the radio working when you got it? What I like to do is fix any safety and power supply issues (electrolytic caps, check transformer, replace cord, etc.) and then try it out with a dim bulb tester. At this point you can look for unlit tubes or tubes in the wrong sockets, etc. This way I have a starting point. If one just replaces everything first, it seems too easy to make a mistake (or not know if some else messed eveything up) Just one man's opinion as RR would say.
Next if nothing works, or it works poorly, I measure the voltages. If any are wrong I try to figure out why. Bad cap, bad resistor, bad tube, etc. You can inject an audio signal at the top of the volume control. This divides the radio in half. If you can hear the audio, you know the speaker, audio transformers, and the whole audio chain is good. If no sound or it is distorted you have only half the radio to troubleshoot.
Next comes the "radio" part. You can inject RF at various points. I sometimes start with the IF frequency right at the top cap of the IF amp. Whever the signal stops getting through, that's where the bad part is. There's more to go wrong here. Coils can open. The oscillator can refuse to run. I check this with another radio. You can hear the oscillator signal or a harmonic. Band switches are often dirty. Grid caps can come unsoldered. Resistors and caps can be bad. Eventually you can narrow the defective part down.
Once I get the radio going, I'll replace all the caps, except the micas, and any out of tolerance resistors. About half the resistors may be out, maybe fewer.
You mentioned blown fuses. Where were these fuses?
You said at one point the radio would pass an audio signal. Will it still do that?
When the fuses blew was anything burning?
I think the voltages look OK. Chuck or Ron will know for sure.
Have you done any of the other checks I mentioned above?
If you have replaced multiple components all at once, I think you are really going to have to trace the signal chain. One missing part can break it. Start again with audio (assuming nothing is letting out smoke) and let us know if you can pass a signal.
Keep trying. I'm basically self taught. If I can do it (I've done over 50 Philcos now) you can too. Chuck will let us know if I'm on the wrong track.
Steve Chambers
Chuck will have the most knowledge here, but I'll try to help if I can. Forgive me if my questions make you repeat yourself, but it might be the best way to proceed.
Was the radio working when you got it? What I like to do is fix any safety and power supply issues (electrolytic caps, check transformer, replace cord, etc.) and then try it out with a dim bulb tester. At this point you can look for unlit tubes or tubes in the wrong sockets, etc. This way I have a starting point. If one just replaces everything first, it seems too easy to make a mistake (or not know if some else messed eveything up) Just one man's opinion as RR would say.
Next if nothing works, or it works poorly, I measure the voltages. If any are wrong I try to figure out why. Bad cap, bad resistor, bad tube, etc. You can inject an audio signal at the top of the volume control. This divides the radio in half. If you can hear the audio, you know the speaker, audio transformers, and the whole audio chain is good. If no sound or it is distorted you have only half the radio to troubleshoot.
Next comes the "radio" part. You can inject RF at various points. I sometimes start with the IF frequency right at the top cap of the IF amp. Whever the signal stops getting through, that's where the bad part is. There's more to go wrong here. Coils can open. The oscillator can refuse to run. I check this with another radio. You can hear the oscillator signal or a harmonic. Band switches are often dirty. Grid caps can come unsoldered. Resistors and caps can be bad. Eventually you can narrow the defective part down.
Once I get the radio going, I'll replace all the caps, except the micas, and any out of tolerance resistors. About half the resistors may be out, maybe fewer.
You mentioned blown fuses. Where were these fuses?
You said at one point the radio would pass an audio signal. Will it still do that?
When the fuses blew was anything burning?
I think the voltages look OK. Chuck or Ron will know for sure.
Have you done any of the other checks I mentioned above?
If you have replaced multiple components all at once, I think you are really going to have to trace the signal chain. One missing part can break it. Start again with audio (assuming nothing is letting out smoke) and let us know if you can pass a signal.
Keep trying. I'm basically self taught. If I can do it (I've done over 50 Philcos now) you can too. Chuck will let us know if I'm on the wrong track.
Steve Chambers
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