Fender Super60 volume surge on power off

[sonicmojo]

I've got a couple of Fender Super60s that I'm trying to get totally right. One of them has a weird issue on power off. When I power it off, the volume surges up to about 11 for a few seconds and then subsides. If I put it on standby for a minute before power off, this doesn't happen.

It's not a big deal but I'd like to correct it. Does anyone have a suggestion on what I should look at? These things are a bear to work with the upside down PCB so it would be trial and error debugging. My first guess is a filter cap discharging very quickly? The amp sounds great otherwise.

Thanks!

[selloutrr]

capacitors. possibly a burned resistor. the good news you have two so you can use the good one to follow as you meter through the amp.

also you might want to try powering it off with the amp openned up and the lights off and see if you can see any sparck or arching on the PCB to help identify the area of problem.

chop sticking the board may or may not give you an answer. Being that it's a PCB not only do you have component failure to consider you also have PCB moisture, trace arching, and just over all poor layout. it might take hard wiring a threw runs for better isolation. even though one amp works great it's possible the other PCB was not perfect in manufacturing.

Hope I didn't scare you. I'd check the capacitors and work from there.

[sonicmojo]

Nah, not scared of it. The PCB and all the solder joints look like someone sweated on it and the left it outside to rust a few weeks. Amazing it works at all really. Thanks for the suggestion. This thing is kind of tricky to measure with the upside down PCB but t is possible Trying to meter a small solder dot aurrounded be a bunch of others while it is running is tricky. I'll have to flip it and mark out everything first. Flipping it requires I disconnect a bunch of stuff first so no way to power it on flipped.

[selloutrr]

rust could be the reason it's arching.
as well as the sloppy soldering.

I'd start by cleaning up the board, entire amp really. make sure everything it clean, lubricated, and tightened. then go at it if needed.