OK, in between working on the PF, I have played a few games on my LAH today....The humming on the sound is starting to get to me..

At this stage I've only replaced the one cap on the sound board (as per Clay's guide)...All backbox pcb screws are present and tight (even bought some new ones from Mark)...The two connectors which attach the screen display / speaker panel are on and tight to the metal tabs.

My question is  - will replacing the -12v caps on the power supply have any assistance?  Or should I look elsewhere?

Thanks guys