These sound boards don't have a BR that I can recall.

You need to check the connectors and resolder the board connectors.

They have three separate amplifiers - unusual that all three would be defective which leads to the PAL chips which can be replaced but only with the proper desoldering station as these are fickle boards to repair. The fact that the IC reseating solved the problem leads me to think it could be the ROM Sockets.

Try reseating one at a time to see if you can narrow it down to one particular IC or socket. ROMs can be re programmed - but I still think it could be as simple as the power connector on the board - resolder to be sure.