Working on a neighbors JC-120 and getting no sound from the reverb tank (or the distortion pot) and flipping the tank over to take a peek and was greeted with this colorful tag.
I recently bought a Peavey Classic VT Series from the late 70's early 80's for cheap and the last month I have been working on getting it running again. It came with no tubes, so I bought some new tubes and after installing them there was a very loud hum sound and very little guitar sound even at full volume. I changed all the electrolytic capacitors on the power supply and it did not help. I eventually was able to trace the issue down to the 15V power that powers the preamp. The schematic is in the picture and I replaced all of the components on the preamp board (IR11/12, IC15/17, ICR10/11) for this power supply. After replacing these parts it took away the hum and volume went back to normal, so it seems that was the issue. However, after playing around with it for about an hour all of those replaced parts were pretty hot, especially IR11/12 (these are 5W 100 Ohm 5% Power Wire wound Ceramic Horizontal Cement Resistors). Not scalding hot where I could not touch them, but hot enough that I would not want to hold my hand on it for an extended amount of time. The voltages seem to be within range for the parts prior to this on the power amp side, and the voltages coming out and on the op amp are slightly over 15V at about 15.8V, so it seems everything is working as it should. The tubes are also extremely hot (especially as compared to my Peavey Heritage VTX, that is only a few years younger. It does have 4-6L6 tubes, as compared to 2 on this one). I've read that these amps do run pretty hot, but this seemed a little more than normal, but maybe that's just the way they are. Does anyone have any experience with these amps and is that normal? Does anyone know if there is a temperature range that is too hot?
I also get a lot of hiss once the gain hits about 4-5, especially on the bright channel. I have a few capacitors I plan to change on those circuits that may help, but is this normal for these amps? Could the two issues be related?
Free circuit Friday! Every Friday ill post a schematic I have designed & built in Kicad
Have good weekend fellow tubies!