Fender Roc 1000 changing channels when played.

[g1]

A heat gun/hair dryer may also prove useful, although if it only does it at high volume, then that does imply that it is a vibration rather than heat issue.
But some heat might speed up getting the fault to show up.

[Enzo]

And for that matter, even if the parts are not thermally sensitive as regards the problem, hitting them with freeze spray also sends a shock through them, whoch MIGHT reveal something.

[Danglin' Fury]

OK, so... I ran a wire from the zeners. Got one for the +16 volts and one for the -16 volts. hooked up 2 meters and.... The +16 volts stayed strong. The -16, on the other hand, was all over the place when the channel changing event took place. And that was after I paralleled 2 zeners for the +16 and 2 paralleled for the -16 for heat dissipation. So the negative voltage is the ONLY one fluctuating. I had to play guitar through it to change the channels. The function generator wouldn't do it. And, once again, only inside the cab and only at loud volumes with palm mutes ringing out. Any other ideas? I'm going to be the Ohm Ranger and see what I can find.

Oh yeah, pounding the hell out of it with a rubber mallet totally makes it change channels.
And Im still only losing the -16volts

[Danglin' Fury]

I FIXED IT!!!! It was a damn hairline crack on one of the solder pads of the big 10 watt resistors right after the rectifier. And I hit that one with an iron too. Oh well. Thank you everybody on here that helped me. I love all you guys!!!! Strictly platonic though.