Your +12v and -12v supplies are fine. If these were low, the amplifiers on the sound board would start cutting out, causing the sound to pop in and out completely. Your +5v supply is also fine, or else you would hear the power up sound repeatedly. You stated you already verified the sound ROM checksums to be valid. Your sound board likely has a bad address decoder chip or some other logic issue. I would suggest sending it to Clive at Coin-Op Cauldron for repair. He has repaired a similar issue for me and has even guaranteed his work with a free follow up fix when a second issue arose with my sound board.
(Topic ID: 253579)
