Just picked up a Monte Carlo to restore and at some point during the game play, usually after a pop bumper is hit, the machine starts making a high pitch sound. It starts out low and gets louder. I have read a few posts that this could be due to a bad driver board or possibly cracks in the solder on the power supply. I reflowed the power supply board, but that did not fix the problem. Sound board seems to be fine. Does anyone have any experience with the system 80's and encountered this issue? Thanks!