mvs sound problem..

I have a one slot medium size, when you boot a game for example pulstar the neo geo logo sound is fine and the background music is fine but when you start too shoot or even in demo mode all sound effects go beep beep beep , this is the same on all carts, I have another one slot with a video ram error ,does any one know which chips I could swap around too make one good mvs board thanks...

Sounds like a voltage problem to me. Check the +5v on your PSU, tweak it to as close to 5v as you can.

...Or, failing that...
It "might" be a problem with one of the 2 sound chips,
Most likely the Z80. Check the PCB for loose soldering/
Burn markings/broken connector legs. Use caution when exploring the PCB, static isn't your friend.