SF2 World Warrior A board - sound cutting out

NoAffinity

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Got another problem A board here. The board will start up fine and play fine for an indeterminate amount of time. Sometimes it's 5 minutes, sometimes it's 15 minutes. One time I left it on for about 40 minutes, with no problem. On average, and every time but that once, I would say sound cuts out around 5 minutes. The game continues to play "deaf".

It makes a scratchy noise when cutting out, and then audio is gone.

I've replace the Z80, amp and caps in the audio circuit.

Next suggestions?
 
I had an A board like this, got to the point of almost giving up and then replaced the z80 crystal which fixed it.

Nice. Seems to corroborate what a member at the Arcade Otaku forums responded to my parallel posting there:

"I had the same problem on 2 A boards.. check the clock to the z80 when the sound cuts out. If I remember correctly it lost clocksignal after 1-15 minutes randomly playing perfect.. cant find the log now check pin 6 with a scope of logic probe."

Where is/which one is the z80 crystal?
 
If you're looking to buy one I think the correct name is an oscillator when it's in a 4 pin package (I always just call them crystals). It's a 3.579545 mhz, I took one off a scrap board.
 

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If you're looking to buy one I think the correct name is an oscillator when it's in a 4 pin package (I always just call them crystals). It's a 3.579545 mhz, I took one off a scrap board.

Cool, thanks! I've got a scrap CE A board. Wondering if it's the same crystal. Will have a look, and likely try the swap tonight or tomorrow morning.
 
Just a quick update on this. Been testing through the circuit, with advice from a member at Arcade Otaku forums, and making some progress without shotgunning parts.

1) Checked the interrupt pin on the YM2151 before and after sound failing. Before, it is pulsing normally. After, the signal goes high w/ no pulsing. Interestingly, removing the logic probe causes sound to return temporarily. Continuing to probe with sound working, and it gets scratchy with signal going low and high and basically freaking out. Other times, it continues working fine and probes correctly (Logic "1", with negative single pulses)
2) Checked resistor R52, which is in the line feeding current to the open collector on YM2151. It tested good - labeled "472", and measured at 4.68k resistance.

Next and final check is to measure the trace from the Z80 pin to the YM2151. If that checks out okay, then time to replace the YM2151.

More to come....
 
the YM2151 is only the FM synth component, there's also the MSM-6295 digitizer. you've already replaced the Z80, amp, and caps.

have you looked into the volume pot itself? without that you'll have no sound.
 
the YM2151 is only the FM synth component, there's also the MSM-6295 digitizer. you've already replaced the Z80, amp, and caps.

have you looked into the volume pot itself? without that you'll have no sound.

I've played with the volume pot when sound has failed, and it has no affect. It is working normally when sound is working normally as well. Is there a reason to believe it would be the culprit?
 
I've played with the volume pot when sound has failed, and it has no affect. It is working normally when sound is working normally as well. Is there a reason to believe it would be the culprit?

that's the only other common denominator I can think of if your entire sound is messed up. you replaced everything else.

different hardware, but a SF3 3rd Strike at work would have the audio go scratchy, quiet, or cut out entirely. simply wiping the volume pot had no effect, but once I hit it with deoxit it never messed up again!
 
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