I'm working on a squawk & talk board that got hit with over voltage. I bought the machine as a project and my guess is the 5V got over voltage as all the boards have problems. This board makes some sound but has lot of high pitched screeching. I can heard the background/feature sounds and all the "talking" sounds like static. The LED flashes correctly. It has been recapped and needed a new 2002 amplifier. All the socketted chips test good in another board. Any good guesses on how to proceed?