There's no working sound on the A board for Slam Masters. That A board has the whole sound section unpopulated and it has a different sound PAL on it since it has the Q-Sound board in it instead.
If it's dead you should be able to get it phoenixed.
As for the CPS1 with no sound, an A board might not solve the issue. The sound program ROM and the digitized sound ROMs for the OKI chips are on the B board. If the sound Program ROM is bad then that's not on the A board.
RJ