CPS1 A board no sound output repair

[arcadeqc]

I have a CPS1 A board that plays well and outputs video, but no sound. Does anyone have experience repairing the sound portion of CPS1? Pointers, tips, repair logs greatly appreciated!

 

[ekorz]

No music no fx no nothing? If you turn up the amp can you still hear a hiss? If so I’d start with the z80. Also easy to check the audio roms but the z80s fail a lot

 

[xodaraP]

No music no fx no nothing? If you turn up the amp can you still hear a hiss? If so I’d start with the z80. Also easy to check the audio roms but the z80s fail a lot

This.

I've also seen the amp go bad, but the Z80 is where you start. They used a Z80 but built the sound system (and silkscreened it for) a Z80A. So the lower rated Z80s have been running overclocked for 30 years

 

[arcadeqc]

Ok, thanks for the input guys. When I crank up the sound, it does have a hiss to it. Inspecting the board it seems that the Z80 has already been socketed and the chip in there is a Z84C0020PEC. I'll look into replacing that. Is the part I should replace it with the Z84C0006PEG, in DIP 40 pin package?

 

[xodaraP]

Z84C0006 would be a 6mhz Z80A I think, so that should be fine.

The current one is a 20mhz processor.. are you sure it isn't Z84C0002PEC? 2mhz? I would replace it anyway as they do fail and see where you end up from there

 

[arcadeqc]

Yep, I'm positive it looks like the 20MHz version