Fix for dead CPS-1 audio...

ifkz

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So, I started with a Street Fighter II: WW board I brought 100% back to life from a bunch of parts. After I took the board out to add EPROM stickers, I put it back in my bartop and found the sound was out. Two hours pass troubleshooting.

In the end, I found the issue. If one of the B ROM board resistor jumpers is not attached during powerup, it can lead to completely dead audio. If contact is made during the game, the audio is still dead. I'm sure this can be the cause of other issues as well. These resistor jumpers are off white in color with a black band, arranged in groups of four.

My boardset has been knocked around a lot and the jumper was just sitting on the metal pad, making enough contact for it to work. It will be fixed properly tonight. Something easy to look for when troubleshooting CPS-1 boards.
 
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Those jumpers are for selecting which ROMs you are using - either JEDEC or non-JEDEC types. If they are in the wrong spot then the Z80 won't boot.

Other common causes of problems with the audio circuit on CPS-1 are:
  • Z80 CPU is dead (should be a faster Z80A)
  • bad electrolytic caps in the audio circuit
  • fried audio amplifier ic (check for miswiring in cab)
  • bent pins between A and B boards
  • gouged traces on either A or B board
 
+1 on the blown Z80 suggestion - have seen dozens (literally) of CPS1 boards with blown Z80s, sometimes they make squawking noises, other times they are totally silent.
 
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