Possible Bad PCB, any ideas?

[daz]

This is a question that possibly cannot be answered here, but I have no idea so I am throwing it out.

I have a full head on machine. The year shows 1979, mftd by Gremlin. Sideart is in decent shape, Black & White monitor. I really dont want to mame the machine since it is complete.

http://www.klov.com/game_detail.php?letter=H&game_id=8090

My wife has instructed me to clean up what I have before I can even think of going to the upcoming auction in october so I took it out of the corner of the garage and started to clean it up and work on it last weekend.

When I powered it up, it made a very loud screeching sound.
So I unplugged it, blew out the cabinet to get it clean, removed the pcb and cleaned it as well as I could with isopropyl alcohol, let it dry and tryed again; same thing but screen came up. disconnected the sound board so I could stand to see what was going on with the monitor. The screen comes up with garbage, you can tell that the board is active though because when you trigger a coin insert, the screen changes. I reseated all of the eeproms (or whatever they are called) and checked for possible broken traces, couldnt find any. Another thing of interest is the led on the board, sometimes it is on, other times not unless you insert coin or repower cabinet.

Any further ideas on what I could check? I spent quite a bit of time with it, but came to the conclusion that I dont know what I am doing... I can post pictures if needed.

Any ideas are appreciated...

Jesse