12-02-2007, 12:43 PM
I have just restored a Model 80 with new electrolytics and replacement of all dogbone resistors (including Ron's Model 80 resistor mods). It looks like this one had its electrolytics replaced, as the original cans were empty and some axial caps were installed underneath (50's vintage caps). I also found that a gimmick was already installed on this unit with the same type of wire as the original wire. Could some of these Model 80's had gimmicks installed in later production runs? The radio pulls in many stations and sounds fantastic, except...
Every couple of minutes or so the volume drops off a bit and I eventually here a "pop", followed by a return to full volume for a few more minutes. I have seen others refer to this occurring on other models in this forum but have been unable to find a description of what might be causing this. Is it a failing rectifier tube or some other component in the DC supply section? The only one I haven't replaced is the 325 Ohm wirewound resistor to ground. Also, I haven't touched any of the bakelite condensors.
Any hints on this would be very helpful. Initially, I just chalked this up to "expected 75 year-old radio" performance. But, it seems like a problem that should be fixable.
Every couple of minutes or so the volume drops off a bit and I eventually here a "pop", followed by a return to full volume for a few more minutes. I have seen others refer to this occurring on other models in this forum but have been unable to find a description of what might be causing this. Is it a failing rectifier tube or some other component in the DC supply section? The only one I haven't replaced is the 325 Ohm wirewound resistor to ground. Also, I haven't touched any of the bakelite condensors.
Any hints on this would be very helpful. Initially, I just chalked this up to "expected 75 year-old radio" performance. But, it seems like a problem that should be fixable.
