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Need assistance fixing a CPS2 A board (game only loads randomly, never any sound)

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Stupid Dufus

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When I first joined I posted about it under the Darksoft multi support thread.. but really, it's a general A board problem, not related to the multi at all.

Anyway, the issue:
Bought as junk from YAJ with a working B board.

A board only powers on randomly with a game with full ROM set populated. Doesn't produce sound at all, regardless of setting mono or Q sound/stereo. No sound from JAMMA edge or RCA jacks. I've tried powering on with volume down held with no change.

If I connect a B board with the Razoola Suicide CPS2 test ROM, it powers on and displays text every time... but sound ROMs show an error, and no audio plays. But there are rare occasions it starts with no error, but still no sound.

I already did a shotgun approach and replaced all the capacitors in the sound section of the board with no change.

Attached are pics of the junk A board. When I compared it to my separate working A board, I noticed that this junk one has the CPU in a socket... and the CPU is labeled differently?

Is that different CPU the issue? Or is there something else I could try?

I don't have a logic probe or scope, so I imagine that makes things more difficult to diagnose.
 

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Replacing the capacitors won't help if the board isn't able to read the sound ROMs.

The reason the Z80 is socketed is because this is a common cause of sound failures in CPS1 so someone has performed the same fix here to see if it worked.

It's still entirely possible the CPU is at fault but I'm not sure if a standard Z80A will work or whether you need the Kabuki
 
Hmm, guess I'll look and see if I can find a replacement z80 and give that a shot.
 
I compared the broken and working A boards.

On the broken one:

  • Labeled as "93646A-6"
  • All PALs are socketed, as well as the z80 (as mentioned above)
  • The PAL closest to CN3 (above the z80) is labeled as "D8L1" but the label on the A board itself says "bGSA3). All other PALs match up with the labels on the board.
  • The z80 is a DL-030P-110V Kabuki. Right next to it, JP3 is jumped/soldered for "DL-030P".
  • Has more "CCX" capacitors (25v 10 uF) installed than the working one

On the working one:

  • Labeled as "93646A-7"
  • Nothing is socketed. It's all soldered directly to the board.
  • All PALs match the labeling on the board.
  • The z80 is a z0840008PSC. JP3 is open.


I don't have a programmer to read PAL/GAL, so I can't dump to verify it's correct. And really don't want to desolder from the working one and swap parts out.

Thinking of going ahead and ordering a replacement z80, but anything else to check in the meantime? The four connectors that the B board connects to all look clean, no bent pins. I don't see any scratches or broken traces either.
 
Well, I got the new z80 in, and no change. Still no sound. Street Fighter Zero does its initial checks and hangs on the Q Sound check.

Any other ideas on what I could check or try? Any chips I should maybe try reflowing the solder on?
 
Sorry, I should've stated.

I replaced with a standard z80 that looks to be a match with what is in my working A board. I undid the "DL-030P" jumper as well.

If you need close-up pics of anything, I can try and take some.
 
Hmm. If it's freezing on the initial checks that points to a RAM or ROM issue. Since you have tried the B on a known good A that leaves RAM as the next thing to look at, especially since you replaced the CPU.

It could also be the Q Sound processor since it would also explain the issues you're having
 
I imagine the big ""CAPCOM-Q1" chip is Q Sound processor, but would you be able to point out the ram?
 
I'm not actually 100% sure myself but I would assume it's the 6264 SRAM in the sound section next to CN3

In photo 2.jpg - Fujitsu MB8464

One of the 2 PALs could also be bad

Also and I only noticed this recently, what on earth did AT&T have to do with Q Sound?
 
Well, I reflowed all the pins on the Q sound chip.. and it boots now every time!

However there's still no sound regardless of mono from jamma or stereo through RCA jacks on the A board. I've tried changing settings from mono/stereo (q sound) with no difference.

Guess I'll try reflowing more pins?
 
Good start - what does the suicide test say now? Same as before?
 
Also try putting the Kabuki back on, that revision may need a Kabuki rather than a standard Z80
 
Put the kabuki back on, soldered the jumper for it. Also reflowed the pins on the ram chip you pointed out.

Still no sound.

All my boards have an infinikey installed now, so not sure if suicide test will work? I'll look for the test chip I burned and give it a shot anyway and report back
 
No, don't solder the jumper for Kabuki, that's to enable encryption so with that soldered you will get no sound.

Encryption wasn't used in sound for any CPS2 games even though they added it a potential option

They used Kabuki CPUs because they had loads of them still around from CPS1.5 - but they disabled the encryption option and they then operate as a standard Z80
 
Thanks for the background on the kabuki usage. I had no idea!

Suicide tester didn't work, but I'm guessing that's because of the infinikey.

I undid the jumper, but still no sound.
 
Do you have any way of connecting the RCAs and checking to see if sound is coming out in stereo just not over the JAMMA edge?
 
Yup! With each change I make, I've been testing it via jamma edge (going through HAS through a SCART cable to gscartsw, which feeds into some speakers) and RCA outputs of the A board straight to the speakers.

Either way, no sound. And I'd read before that RCA outputs don't work unless you set sound to stereo (q sound) in the settings.. which I've been also been toggling off and on.

¯\(o_O)/¯
 
Ok at this point I'm going to say you need a logic probe or a scope. You need to know where audio is and isn't working (if at all) to track down the fault
 
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