Here’s an issue I ran into that I’ve been trying to help a buddy solve for a few months. Hopefully this can save you a ton of headaches.
The backstory. My buddy got a South Park pinball without a logic board. He sources a board and ROMs, puts it in and everything works except sound. It’s screeching, popping, missing sounds and making wrong sounds. He gets another logic board that works fine with the Space Jam ROMs it came with but when he puts in the South Park ROMs it has the same sound issues.
Thinking theres a problem with the ROMs, he gets another set only to have the same problem. Two boards, two different ROM sets, same problem.
He asks me to burn another set suspecting a corrupt file is floating around online, but I’m not so sure. I have him send me the board so I can checksum the ROMs. Sound ROM U7 is corrupted. I burn a new one, send the board back and hope for the best. Nope, same problem. This is just a few days before Christmas so I suggest we get back to it after the holidays.
In the meantime I look into it a bit and notice there’s some jumpers for the sound section, but they aren’t documented too well except for J4 and J5 which select the RAM size. I suggest he looks into it. He ends up bringing the entire game to me so I can look it over. Before this I didnt have access to a Whitestar system game to test the board in.
Now that I have the game in hand I can confirm the situation. Two boards doing the same thing. Only this time I have a Stryker Extreme that I can experiment with. To verify that it isn’t the speakers or power supply (I already verified all voltages are present but wanted to be double sure) I put the board into the Stryker and get the same thing. I decide to swap the South Park ROMs into the Stryker board and viola! All sounds are present and correct. So now I know there’s nothing wrong with the ROMs. I also swap the Stryker ROMs into the South Park board and its screeching, popping and having the same issues. I take both boards to the bench to see what’s up. They are different revisions. The South Park board is a 520-5136-00 REV-D and the Stryker Extreme board is a 520-5136-00 REV-E.
Other than different revision numbers and one is marked SEGA and the other STERN, I can’t see any differences. The chips and layouts are the same and the PAL’s are the same versions.
Looking a little closer I notice another jumper, J6. On the Stryker board it’s populated, on the other two boards he brought to me they aren’t, with one exception. When I suggested adding the jumper to the South Park board he says he tried it but it locked the board up. When I looked a little closer, I noticed it was just a bare wire that actually looked like it was touching an adjacent trace.
On a hunch, I decided to try it anyway. BAM! All sounds present and working correctly. So some further digging revealed Space Jam uses smaller sound ROMs than South Park and Stryker Extreme. Space Jam uses 512k sound ROMs and South Park and Stryker use 1024k, The jumper is for ROM size. I can’t say I can remember having to change jumpers on Whitestar games in the past.
If you’re doing a board swap, check your J6 jumper and install it for games with 1024k sound ROMs and remove it for 512k sound ROMs.
Maybe you’ve dealt with this before. If you have, I’d like to hear about it, please let me know below.
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