My radio was working great, and I had it on for about 30 minutes today when suddenly it stopped working. No static, no hum, nothing. I've been fumbling with it all day with my limited knowledge, and found that when I tested all of the grid plate test points, I was getting almost double voltage on almost all of them including about 600V at the rectifier where it shows I should get around 300. I've tested all of the resistors and they seem good. I've already recapped and all tubes test good. When I went to check voltage after it had been shut down for quite some time, the radio began to work again. Could the high voltage be overheating something and causing it to stop working? Does this sound like the power transformer is bad? Thanks,
Mike
Posts: 48
Threads: 7
Joined: Jun 2007
City: Seabeck, Wa.
Boy, That's a weird one. At first, it looked like it might be a bad/intermitent connection at the 35 ohm section of R43, which would unload the power supply with no voltage drop across the field coil or op transformer primary. Still can't get to 600v. Tried to make some kind of voltage doubler out of C45 and C15a, couldn't make that work either. Be interesting what the experts say. Are voltages approximately correct when the set is working?
Well, this is a bit embarrasing, but I was measuring ACV not DCV like I should have been. So voltages check good, and the problem hasnt repeated with hours of use. I'm thinking there was some kind of short at the field coil or output transformer. I did nothing more than let it cool completely, and fiddle with some wires around the field coil. Well it works again, so I won't try to fix it. Also finally found the short that was causing my 89L to stay silent since I bought it. I'm listening to it now for the first time. All in all a pretty good day!
Mike
