SF2 World Warrior A board - sound cutting out

PCB problems and fixes
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Re: SF2 World Warrior A board - sound cutting out

Post by NoAffinity »

Finally got back around to this. I ponied up for a Hakko desoldering gun, which they had on the shelf at our local big box electronics store. A bit of an expenditure, but well worth the investment already, just in the time saved desoldering parts from boards in this effort alone (and I've got plenty of other projects lined up that it will make quick work of).

Okay, back on topic. I pulled the SRAM and YM2151 off of a parts board, which had working sound but graphical glitches due to a failing custom chip. I soldered them on, and still have the same problem. :cry:

What next?
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Re: SF2 World Warrior A board - sound cutting out

Post by leonardoliveira »

Some failed TTL? Any fujitsus? :lol:
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Re: SF2 World Warrior A board - sound cutting out

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leonardoliveira wrote:Some failed TTL? Any fujitsus? :lol:
What should I be looking at specifically on the board - components and measuring?
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Re: SF2 World Warrior A board - sound cutting out

Post by leonardoliveira »

look a photo of the A board from a CPS1.5 game. Look which chips are missing, those will be the sound parts you need to check.
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Re: SF2 World Warrior A board - sound cutting out

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And what should I be testing or measuring at those? Please forgive the noobishness. Again, working through this for the first time, but learning as I go. :thumbupright: :-D
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Re: SF2 World Warrior A board - sound cutting out

Post by leonardoliveira »

A chip programmer which can test SRAM and TTLs is very helpful on this hobby. :awe:
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Re: SF2 World Warrior A board - sound cutting out

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leonardoliveira wrote:A chip programmer which can test SRAM and TTLs is very helpful on this hobby. :awe:
Any good models to be recommended?
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Re: SF2 World Warrior A board - sound cutting out

Post by leonardoliveira »

If you have a chip programmer, yours might already do it.

I think only cheaper stuff like Willem won't test TTLs and SRAM.
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Re: SF2 World Warrior A board - sound cutting out

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leonardoliveira wrote:If you have a chip programmer, yours might already do it.

I think only cheaper stuff like Willem won't test TTLs and SRAM.
Yeah, my GQ-4x4 won't do them. I ordered a G540 tester off ebay. It has mixed reviews, but from what I saw, older reviews weren't good, newer reviews are. So, I'm hoping that's an indication that they've worked out the bugs over the years, and it's now a good low-cost solution. Plus at $50 shipped, I'm willing to take the gamble. At $500+ for a higher-end model, I'm not even a player.

Hope to be reporting back with good news in a couple weeks, both with regard to the tester and the board.
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Re: SF2 World Warrior A board - sound cutting out

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Circling back on this, almost a year and a half later. This board had been relinquished to a "maybe I'll get to it someday" pile, but I am happy to report that the problem is solved. The resistor at R53 was out of spec. It is supposed to be a 560 ohm resistor, but when pulling and measuring it, it measured at 860 ohm. I then pulled the same resistor off a parts CPS Dash board, and it too measured at 860 ohm. Checking the labeling on the resistor (561), it is indeed supposed to be 560 ohm. So I pulled yet another R53 off of a working board, and it measured at 660 ohm. Well, if these things are 20% tolerance then that is probably within spec. I swapped it onto the board with audio that would cut out after a random period of time, and it is now working with no disruption to audio.

Theoretically, it seems this location has pretty high tolerance, and presumably at 860 ohm, the circuit was still functioning normally, but once heat was introduced through operation, it would reach some threshhold of increased resistance that would result in failure of the z80 clocking.

Interesting that 2 boards had the same resistor failed. Hopefully this helps someone else down the line. Now to order some 560 ohm resistors for my stockpile. :)
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Re: SF2 World Warrior A board - sound cutting out

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Did you replace the 3.58MHz oscilator?I guess your is branded JVC.I remember some time ago I fixed two A-BOARDs with sound cutting out and the culprit was two bad 3.58MHz oscillator from JVC.
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Re: SF2 World Warrior A board - sound cutting out

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caius wrote: August 18th, 2018, 7:23 am Did you replace the 3.58MHz oscilator?I guess your is branded JVC.I remember some time ago I fixed two A-BOARDs with sound cutting out and the culprit was two bad 3.58MHz oscillator from JVC.
I don't believe that I did, but it is possible that I swapped one off another board at one point, shotgunning various parts. I'll have to remember this, though. Did you replace with oscillators that were an exact match for the originals? Do you have a link to the replacements you used (or were they also pulled from other boards?). It never hurts to have spares. :) Good info!
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Re: SF2 World Warrior A board - sound cutting out

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I don't believe that I did, but it is possible that I swapped one off another board at one point, shotgunning various parts. I'll have to remember this, though. Did you replace with oscillators that were an exact match for the originals? Do you have a link to the replacements you used (or were they also pulled from other boards?). It never hurts to have spares. :) Good info!
You replaced everything except the most suspicious part :)
Any oscillator with same feequency and package is fine.
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Re: SF2 World Warrior A board - sound cutting out

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caius wrote: August 20th, 2018, 3:22 pm
I don't believe that I did, but it is possible that I swapped one off another board at one point, shotgunning various parts. I'll have to remember this, though. Did you replace with oscillators that were an exact match for the originals? Do you have a link to the replacements you used (or were they also pulled from other boards?). It never hurts to have spares. :) Good info!
You replaced everything except the most suspicious part :)
Any oscillator with same feequency and package is fine.
If I didn't replace it, it would have been because I probed it, and was getting a pulse out of it even after sound cut out. For future reference, am I correct in thinking if a pulse is there, the oscillator is working, and if the oscillator is to blame, there will be no pulse? Or could it be still pulsing but not correctly? Did you see that in either of your cases, or were they all or nothing?
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Re: SF2 World Warrior A board - sound cutting out

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A bad oscillator can still output some kind of signal, see this repair log of mine for example:

http://www.jammarcade.net/out-zone-repair-log-6/

I'm pretty sure this is the problem on your board.
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Re: SF2 World Warrior A board - sound cutting out

Post by leonardoliveira »

NoAffinity wrote: August 20th, 2018, 8:46 pm
If I didn't replace it, it would have been because I probed it, and was getting a pulse out of it even after sound cut out. For future reference, am I correct in thinking if a pulse is there, the oscillator is working, and if the oscillator is to blame, there will be no pulse? Or could it be still pulsing but not correctly? Did you see that in either of your cases, or were they all or nothing?
That's why burn-in-tests exist, to aid on diagnosis of intermittent faults. Which would be the case with the oscillator fault mentioned by Caius. Both the Z80 and the YM2151 chips have dynamic ram cells inside for their internal registers. If the clock fails for a long enough while, even if it comes back later on, the data stored on their registers will fade out and because the chips will lose their internal state they will crash and stop operating properly until the board is reset again.
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Re: SF2 World Warrior A board - sound cutting out

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Thank you for the additional color, Leonardo. I'm glad I have the real experts looped in on this thread. :)

After many hours of play testing, many reboots, letting the board run in attract mode with sound on for upwards of an hour (multiple times), the problem came back. This was with only the resistor swapped, which I was sure had solved it.

So, I followed caius' advice, and replaced the 3.57mhz oscillator, taken from a known good board. Actually swapped oscillatorss between the problem board and the known good board. The problem persists on the problem board, and the known good board is still working fine.

So, then, for shirts and goggles, I swapped in a new 12mhz crystal, replacing the native 10 mhz crystal. I have run the problem board now, with the 12mhz crystal, for a burn-in routine at least equal to the point when the board failed with only the resistor replaced.

I know I really need a scope and a good way to separate the boards, to get a more accurate picture of what's going on when it fails, but I haven't quite gotten there yet. In theory is it possible that the 68K oscillator could have an effect on audio?
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Re: SF2 World Warrior A board - sound cutting out

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If the 68000 oscillator had problems then the game would crash (while only sound cuts off on your board) so you can exclude it.You must focus on Z80 as this CPU rules the whole sound system.If you can, hook up a logic analyzer on CPU busses and see what happens when the sound cuts off.You may need to trigger the data acquisition to a certan CPU event.
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Re: SF2 World Warrior A board - sound cutting out

Post by leonardoliveira »

Just to give you a idea about what/how to look, I repaired a System 16 board today which had a bizarre sound corruption problem with the voices playback. The voice roms are read by the Z80 processor through a banking mechanism and then pumped through a I/O port to the NEC ADPCM chip. CPS1 OKI chip fetches sample data autonomously differently from System 16 uPD7759 which needs the Z80 to perform streaming.

I had no logic analyzer here so I could not spy on what the Z80 was doing. But since it was playing the FM sound properly, and the voice data is streamed by the Z80 into the NEC uPD7759 chip the problem had to be the uPD7759 itself or something between the the roms which hold voice data, the Z80 (but not the Z80 itself) and the uPD7759.
s16_voice.png
Following that line of thought the only things that mattered between the Z80 and the uPD7759 were the 74LS244 and the 74LS125 on the above diagram. I decided to pull these two parts and test them on a TTL tester. Funny enough the 74LS244 which were a Fujitsu part was working perfectly. The 74LS125 was SGS but it was faulty. Replaced it with a tested SN74LS125 I had on a parts drawer. The fault disappeared after the part was replaced.

The point of me posting this is mention that you might have a minor/intermittent fault on one of the small TTLs on the sound circuitry.
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