12-08-2018, 01:42 PM
Hi all,
Well I must have blown something in the re-cap. I got this 48D given to me and it was playing quite well. So I tackled it starting with a nice laquer re-finish, looking great, and then went to the caps and a few resistors, pretty straight forward. Not much had been done to it in the past, had orig. electrolytics. Several .05 caps had been replaced long ago.
So I fire it up and I have no signal, just noise, a strong hum/growl not affected by the volume control. Not unusual for me, the trouble shooting starts and it's pretty exciting when I find my goof and the signal comes through. Not this time. This time I haven't been able to find my good and I don't know how to go forward, maybe you can give me some direction.
First, made sure all the dimmers were off in the house, then cleaned all the tube pins (I had used a naval jelly type product on the chassis and thought some remnant could be insulating somewhere), swapped out a couple of tubes that I had seconds of, the others going by my Hickok tester. Because it worked before the re-cap of course the first thought is an incorrect wiring, but I took pictures and drew sketches as I went and with those and tracing everything with the schematic, cannot find an error. Checked the tuner fins for short. I attached an ipod to the volume pot and recieved great sound so the af section is ok? All the while there is this loud hum/growl uneffected by the volume control. I can put an rf signal from a sig. generator into the antenna wire and get a very low signal out of the speaker again with the hum/growl overwhelming it. Plate and heater voltages are all there. There is no voltage on the secondary of the 2nd I.F. transformer.
Because it worked before I started it's likely something I did, like short something. Please, I hope that you can send me in a good direction.
Thanks,
Alan
Well I must have blown something in the re-cap. I got this 48D given to me and it was playing quite well. So I tackled it starting with a nice laquer re-finish, looking great, and then went to the caps and a few resistors, pretty straight forward. Not much had been done to it in the past, had orig. electrolytics. Several .05 caps had been replaced long ago.
So I fire it up and I have no signal, just noise, a strong hum/growl not affected by the volume control. Not unusual for me, the trouble shooting starts and it's pretty exciting when I find my goof and the signal comes through. Not this time. This time I haven't been able to find my good and I don't know how to go forward, maybe you can give me some direction.
First, made sure all the dimmers were off in the house, then cleaned all the tube pins (I had used a naval jelly type product on the chassis and thought some remnant could be insulating somewhere), swapped out a couple of tubes that I had seconds of, the others going by my Hickok tester. Because it worked before the re-cap of course the first thought is an incorrect wiring, but I took pictures and drew sketches as I went and with those and tracing everything with the schematic, cannot find an error. Checked the tuner fins for short. I attached an ipod to the volume pot and recieved great sound so the af section is ok? All the while there is this loud hum/growl uneffected by the volume control. I can put an rf signal from a sig. generator into the antenna wire and get a very low signal out of the speaker again with the hum/growl overwhelming it. Plate and heater voltages are all there. There is no voltage on the secondary of the 2nd I.F. transformer.
Because it worked before I started it's likely something I did, like short something. Please, I hope that you can send me in a good direction.
Thanks,
Alan
