There have been a number of con artists on EBay lately charging $125 to repair your Williams 3-6 Mpu boards. These people are frauds and hacks! Do not buy from them! They will try to con you out of more money and send your board(s) back unrepaired. They are fly by night, here today, gone tomorrow and apparently eBay is powerless to stop them. My latest experience is with an Asian guy calling himself Lenny Espitio (an Asian impersonating an Italian? Go figure) Under the EBay name classicgamerepair.
He is a fraud! Do business with him at your own peril.