Crate rfx 65 amp hum

[Rick Ferrell]

Given a crate rfx65 amp partially disassembled with no on off switch.
replaced switch and when turned on it makes a very loud hum. Within 20sec picks up surge from effects board.
Found one spot on circut board that appears to have been very hot.
Unplugging the accessories white loom stops hum and all sound. Have tried some other looms and don't find any change.
Hoping for some direction.
Thanks in advance

[Enzo]

When the loud hum ressults, look at the speaker cone, does it move one way and stay there? In other words is there DC voltage on the speaker?

[The Dude]

Please post a schematic if possible.

[g1]

Schematic here: https://music-electronics-forum.com/...etch?id=815212