I agree with you do a full visual on the electrical and work on the components afterwards with an multimeter to see if there are any problems. Once you know where the problme lies that is causing the humming from the speakers. It could be as well that the IC are not lighting up to get to the POST like what some computers go through.
|Darth Tronage Wrote:If you don't have the manual you can get it here
I'd look for broken or worn wires. Take each of the boards off one at a time and inspect them. Look for burnt or swollen parts. As long as the roms are not faulty I think you would be able to repair it. Capacitors, diodes, etc. should be replicable if faulty. Now if sections of the board are burnt because of something shorting out, that can be difficult to fix.