Peavey Classic 100 help

[robot_trouble]

So I've got a Peavey Classic 100 that's been sitting around for a few years. Mostly because the Lead channel doesn't work and the Reverb won't kick in. Well, I was poking around last night and got both of those working by grounding R30 as indicated in another post here. So obviously something is wrong in that circuit. Suddenly I smell the bad smell and look down to see R61 and R62 covered by a thick stream of magic smoke. Amazingly, I found two replacements in my pile of junk and swapped them out. Powered it back up, burnt right back up. Damn. Any ideas how to start troubleshooting what could have gone kaput?

[52 Bill]

...grounding R30 as indicated in another post here. So obviously something is wrong in that circuit. Suddenly I smell the bad smell and look down to see R61 and R62 covered by a thick stream of magic smoke.

Un-ground R30. Do R61 and R62 still cook?

Something in there is shorted and is drawing too much current, causing the resistors to cook. R61 and 62 are in the -27 volt power supply, so check filter cap C43, IC U1, Relay K1A, diode CR1, Cap C20.

[robot_trouble]

Jackpot. Short to ground on IC U1. I'm not sure which I'm more amazed by - A: The fact that I pulled all of the other components for test BEFORE I pulled the IC which was visibly burnt on the BOTTOM or B: the fact that I actually had a spare 4558D sitting around from my TS9. I wonder if the sound is any different because of it...

Also, Reverb and Lead channel still aren't working (without grounding to R30)... will have to look into that more. Any ideas?

Thank you so much for your help, Bill.

[52 Bill]

Also, Reverb and Lead channel still aren't working (without grounding to R30)... will have to look into that more. Any ideas?

Did you try cleaning the footswitch jack or using a footswitch? The jack has normally grounded contacts that complete the switching circuits to ground. If they don't close properly they will stop the switch on the panel from working.

[Enzo]

R30 has nothing to do with the shorted IC. And I sincerely doubt the brand of IC will affect the sound of your reverb in any way.

ANd what Bill said. If the panel switch doesn't work and the reverb doesn;t work, then the one thing they share is their path to ground - the footswitch jack. Perhaps the jack is broken, perhaps the ribbon cable to it is messed up, or its solder.