I'm betting a broken ground trace or a failing filter cap, but aside from that, PLEASE PLEASE post back when you fix it Robert!

I find the amount of "how to fix it" suggestions generally outnumber the "well this is what fixed it" posts by a huge margin. I know for me personally, most of my fix it knowledge is well out of date as I downed tools professionally more than 10 years ago. It'd be nice to know how many of my guesses were actually correct!

In the spirit of my request..

Recently my Peavey Ultra was humming intermittently and reverb not engaging, also intermittently. Caps looked OK but solder joints were weak. I re-flowed all the filter caps and gave the reverb relay section a re-flow as well and that fixed both issues.