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jowstni

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Hi everyone. I'm hoping I can get some help diagnosing a problem with a Mercs board (US version). So far all my work has been on the B board, because I currently do not have another Capcom game with a compatible A or C board.

The issue:

The story:
The game worked flawlessly at the seller's house. We transported the cabinet with the mercs board still mounted inside on a flatbed truck for a 2 hour ride. Upon booting up the game at home, the lines/jailbars appeared.

My guess:
The vibrations from the truck ride loosened a connection on the board, or perhaps a loose wire inside the cabinet brushed up against the board causing static electricity.

What I've tried, and what I've noticed:
- Disconnecting and reconnecting A, B, and C boards and doing a flex and press test on these boards. It seems like pressing or moving the C board changes these lines--sometimes better or worse.

- Cleaning and lightly sanding all roms on the B board. As I slotted roms back in one-by-one, booting up each time, the game had no lines until a rom would randomly trigger the lines. Then, the lines would not disappear until ALL graphics roms were removed. It's like the lines were stored in memory somehow. The lines do not appear to be isolated to one rom. Furthermore--without touching the board between bootups--sometimes the sprite lines are there, and sometimes they are gone. The background lines always remain. My supergun/power supply setup always runs at 4.99v or 5.00v, so I am confident it is not a power issue. Plus, it acted the same in the cabinet with a different power supply.

- Using a logic probe to compare signals on removable roms that have similar function or same chip model. The signals seemed to match each other when appropriate. I do not believe there are any broken pins or slots.

- Using a GQ-4x4, I dumped the contents of roms 30, 31, 35, and 36 onto my PC. I compared the data of the original roms to the mame roms, and none of the data is the same. Well, in some cases large chunks of it seems the same, but the way the data starts out is totally different. Is it because the software for the GQ-4x4 does not have the exact models of the chips? How can I reliably check if data is corrupted on the original roms?

All 4 of my original rom dumps did not work in mame. They either produced missing graphics with no game logic running, or the game froze completely, or just a blank black screen on startup. For reference, here are the chips I dumped and the closest models I could find in the GQ-4x4 software.

30:
model on chip: M5M27C100K-2 (Mitsubishi brand)
model in software: M5M27C100K

31:
model on chip: M5M27C100K-2 (Mitsubishi brand)
model in software: M5M27C100K

35:
model on chip: HN27C301G-20 (Hitachi brand)
model in software: HN27C301

36:
model on chip: TC571001D-15 (Toshiba brand)
model in software: TC571000D

If there is corrupt data, do I need to get new roms that match the exact same model? Is there any copy protection or anti-piracy issues I need to work around?



If anyone has suggestions please let me know. This is my first time trying to repair a board with this serious of an issue. I'll keep an eye on this thread, and either way I'll update with any progress.
 
Quick update: I removed all the graphics roms from the B board, with only the 68000 roms (game code) still in, and the same lines are still there. It's just a black screen--no graphics at all--with the lines floating around. The lines match what I assume are the graphics' boundaries/positions. Before I spend money on a whole new CPS1 game, I'm gonna try flashing new 68000 roms (30, 31, 35, 36).
 
Thats probably your C Board. Can you try reflowing the pins on the Big Capcom chip? Good luck!

Also maybe a dumb question but have you tried a different game that you know works well, to be sure that problem is the game and not the monitor or any other circuitry?
 
Thanks for the tips!

And perfectly good question: All my other boards work just fine with my setup.

Here's a picture of my C board. Anything look suspicious? I do have the tools to reflow the pins but... is there any other way to strengthen or put pressure on the connections? lol.

edit: I just looked at all those tiny pins under a magnifier and I did not notice any lifted or broken pins. Still worth reflowing?
 

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I dont see anything suspicious. It could also be the A-01 chip on the A board or something else on the A board. You dont have another A board around, do you?
 
Unfortunately, no.

I was planning to get another CPS1 game, just so I'd have another A board to test with. As far as I know Mercs only shares a C board with a specific version of Street Fighter II, so I don't expect to get a replacement C board.
 
Yes, you'd need either the same C board or a C board plus infinikeys but for A board it's much easier to find, that's why I'd try that first.
 
Thanks, I really appreciate your responses and advice. Helps me focus on what to try next.

I'll pick up another CPS1 game for the A board, and if that doesn't make a difference I'll reflow/resolder the C board chip.

I'll look into the infinikeys for the future, in case this C board doesn't work out.

Thanks again! I hope to update this thread with good results.
 
Let's hope for positive news! Post a picture of the A board before buying to make sure it's a good one.
 
Did you check your power source? Maybe the jostling of the transport caused the voltage pot to change.
 
Did you check your power source? Maybe the jostling of the transport caused the voltage pot to change.
Good call, but I've tried the game on two totally different power supplies and the game has the exact same problem. That power supply in its original cab was messed up, though. The voltage pot was crooked, and in the lowest position the voltage on the 5V rail was something like 5.35 :(

I wonder if that damaged the board over time. I don't know how long it was like that before buying it.
 
Any CPS1 faults I've had pop up on boards tended to be down to the A board. I've had a few I've bought over the years that I thought were broken, changed out the A board and they worked fine.

I'd definitely wait and try the B & C boards out on a verified working A board before doing any more troubleshooting.

Edit - funnily enough, I did think my Mercs board was broken last year and I had similar graphical issues to yourself. Turned out to be the power supply in the end. Replacing that and the board was back to 100% working correctly.
 
Sound good, yeah. Currently hunting for another CPS1 game that won't murder my wallet lol

Glad your Mercs turned out to be working. Now I'm kinda questioning my PSU, although it works with all my other boards and I've already tested Mercs at 4.85 and 5.15 voltage and it's the same. So, it's probably okay.
 
Yeah I've say you've troubleshooted it down to not being the PSU alright.

Out of the broken CPS1 games I had, I'd a SF2: CE also with a very similar graphical problem to you and it was 100% the A board. So I'd say that should sort you out.

A board failure is definitely a bit of a problem these days. I share one single A board now across Mercs, SF2:CE and King of Dragons. At one point I'd enough working A board for all of them!
 
Gotcha, yeah that's rough lol. I joined this forum and I'm trying to learn as much as possible about repairing because I see all these boards failing and I want to stay in the hobby seriously. I didn't realize CPS1 games basically needed to be Frankensteined together before getting Mercs--now I know!

Hope you can scrounge up those A boards.
 
Quick little update: I have since tested Mercs with a truly working A board (from Ghouls n Ghosts). Mercs still produces the same graphical problems :( And GnG works perfectly with Mercs' A board, so I can rule out it being an A board issue.

I still have not tried reflowing the C-board chip's pins, and I don't have a matching C board so I'll save that as a last resort.

My only idea now is to dump/save all the data from the B board chips and check it against the mame roms. I still have my GQ-4x4, but I still don't understand how to find the closest matching chip model in the software. If anyone has some pointers or guides on how to choose the right chip in software just for reading/dumping roms that'd be amazingly helpful.

Progress is slow but I'm still 100% determined to get this board working. Huge thanks to everyone who has helped so far. I'm still learning a lot.
 
have you tried building a replacement 1A PAL. In my experience wide spread graphics issues like this are either a C-Board issue or an issue with that PAL.

anything else (like ROM corruption) would be isolated to only specific sprites.
 
it's not a ROM it's a PLD, and the way they work you can't really dump and confirm. you'd either program a replacement and try that, or swap the PLD onto a known working board.

depending on your specific PCB revision yours might be different than the one in the PLD archive. so check the number that's printed on it.

I had a Merc's board that had bad graphics due to this chip and it used a different version than the one in the PLD archive that I had to track down.
 
Ah, ok, I understand. Thanks for the clarification. Maybe it would be compatible with Ghouls n Ghosts--I'll check into that.
 
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