What's new
By:

CPS1 Dash Board Repair Help

E

edd_jedi

Student
Joined
Jul 12, 2023
Messages
75
Reaction score
65
Location
England
I'm having another go at reviving this CPS1 stack I bought a couple of years ago. It came from Ali Express, and appears to have a genuine 12mhz A board, genuine SF2HF C board, but a "repro" B board (looks too new, the Capcom font is off.) Based on other reports of receiving frankenstein A boards, this seems untouched so I seemed to have done OK. It arrived packed only in foam and bubble wrap (no box!) with a damaged corner, so I had to replace the sound volume pot. There was also a minor intermittent graphics glitch shown below. Due to these issues I (eventually) got a 50% refund, so only have £75 invested in this currently, I figured it was worth keeping to try and save as the volume was an easy repair and the graphics glitches could just be loose connections as they are intermittent.

IMG_6591.jpeg

I haven't had a chance to look at it recently, so today I took the boards apart and found some pretty bad surface corrosion, and even an old bug on the A board!

IMG_6586.jpeg IMG_6587.jpeg IMG_6588.jpeg

I cleaned these up with isopropyl hoping it would solve the graphics glitches, but no joy unfortunately. On the plus side it cleaned up well. I have also tried reseating the EPROMS on the B board, they don't fit very well and even when fully pushed in don't all fully line up nicely, so I'm hoping this may be my issue - poor connections, dodgy chips, or even the fake B board itself. Here's some photos of all three boards cleaned up:

A board
IMG_6599.jpeg IMG_6596.jpeg

B board
IMG_6593.jpeg IMG_6594.jpeg

C board
IMG_6597.jpeg IMG_6598.jpeg

Any suggestions on what I can try next? Does anyone have a genuine B board they would sell or even lend me to see if it fixes the issue?
 
Try the A and C boards with another game.
Probably it's a A chip issue, or Vram if you are lucky.

On the bootleg this fault is usually caused by something bad in the rack of shift registers LS597 or something, this would probably be equivalent to inside the A chip somewhere on an original motherboard.
 
Well after reseating all the EPROMS for a second time, I am getting much fewer glitches which is promising, the most noticeable glitch now is white flashing on Vega's stage background (Spain.) But I just played about 5 characters without seeing any glitches at all. The EPROMs all look very old and the pins are quite tarnished, so I'm leaning more towards poor connections. Before I order a full set of new chips, does anyone know which particular graphics EPROM(s) may be the culprits for the Spain background so I can leave the rest alone and foucs on that one?
 
Here's a couple of stills of the Vega glitch I took from videos, in fact it's not just the background that are flashing white, but some of the sprites too. It only does this for a frame or two, very quickly, once every 5 seconds or so.

IMG_6605.jpeg IMG_6610.jpeg

And here's a couple of photos of other stages with no issues

IMG_6600.jpeg IMG_6611.jpeg
 
I've just noticed it also flashes on the intro, again only for a frame, and always at this exact point of the animation. These are converted / burned Champion Edition EPROMS, either flash faults or degradation perhaps? Might have to invest in a programmer.

IMG_6612.jpeg
 
Can you buy new EPROMS still? Also does anyone have a link to a beginner / idiots guide to flashing CPS1 EPROMS, which programmer to use etc?
 
Not really new, just recycled or NOS. I recommend www.buyICnow.com

djsheep said:
Here's some tips when starting to learn how to repair boards (I'm still learning myself).

1. Firstly, read these articles on AO, they give you the jist of what's involved: https://wiki.arcadeotaku.com/w/Game_Board_Repair

2. Get the necessary tools and get familiar and competent with how to use those tools -- for the board repairs you've listed above, at the very least, you be needing a soldering iron, desoldering gun, multimeter, EPROM burner, logic probe, wick, solder, tweezers, cutters, etc. Here are some threads on this forum with some good recommendations and discussion:

Best, low cost, programmer for most arcade hobbyists to have???
I need a new soldering iron
Beginner Recommendations: Hot Air Gun / SMD Rework
Preferred / Recommended Solder Wire?
Thoughts on this beginner's soldering kit?
Oscilloscope for beginner question

3. Before asking how to repair, it's worth searching the forum, google and other places for repair logs related to the board you're working on. Here's a few places to start you off reading:

https://arcadefixer.blogspot.com/
https://www.jammarcade.net/pcb-repair-logs/
https://wiki.arcadeotaku.com/w/Category:Repair_Logs
https://www.mikesarcade.com/arcade/repairs/
http://newlifegames.net/nlg/index.php?action=forum#5
https://www.aussiearcade.com/forum/...repair-questions/pcb-and-monitor-repair-logs/

4. Compare your ROM chips against MAME by dumping your chips and using this tool: http://romident.coinopflorida.com/ -- If they don't match, they're either dead or you have an undumped version. If they don't compare, try burning the MAME set onto some blank chips and see if that fixes things. This is usually the first step I would advise if there isn't anything visibly wrong with the board.

Good luck, there's a lot of great people on here who can always help out and I hope this helps you out somehow.
Click to expand...
 
After much trial and error, I think I have traced it to a poor connection or possible cold solder joint somewhere between the 3 boards. I started getting sound glitches and sound cutting out completely after a few minutes, and it seemed very unlikely a new fault would develop. So after taking them all apart and reassembling yet again, I have now had it running for about an hour with zero video or sound glitches! Obviously this kind of intermittent issue is very hard to diagnose so I'm just going to try and avoid touching it now, as I seem to have the three boards assembled and happy currently. Will report back if any of the video or audio issues return.
 
Vega and Balrog's stages were the two that usually "flash" almost every time, but it's been on for about 4 hours now and nothing :D

IMG_6882.jpeg IMG_6884.jpeg
 
edd_jedi said:
IMG_6597.jpeg IMG_6598.jpeg
Click to expand...
So while it is now working correctly, the curious side of me still wants to know why it was glitching, and I might have been barking up the wrong tree with the A and B boards, after finding this thread it looks like the C board can cause similar glitches too:

https://www.aussiearcade.com/topic/69755-capcom-cps1-quotcquot-board-repair-pic-heavy/

As you can see above mine has the original (I think) foam around the chip, and with that attached I can't see the pins. Is there any issue with removing this foam, eg is it acting as a heat sink or something? Or shall I just get rid of it.

Also does anyone know if the lower sticker is original, or something that's been added later? I think the sticker on the chip is original.
 
The foam is much stiffer and more firmly attached than I was expecting, any tips for getting it off? Pulling it is bending the PCB.
 
Well that was almost a disaster, ever wish you hadn't started something?! The foam was a real pain to get off, it was stuck really hard, and alarmingly especially on the custom chip pins, I had to use a lot of IPA to get all the sticky black stuff off.

IMG_6933.jpeg IMG_6934.jpeg

When cleaned up, I could see that there was some rust on the bottom solder joints, and quite significant oxidation on some of the smaller chips. I cleaned it all up, noticed the two chips on the left hand side could do with a clean as well, but when removing the second chip one of the legs snapped off :(

IMG_6936.jpeg

thinking I had just killed it, I carried on anyway and and put it all back together, and to my amazement it still worked! Maybe that pin is unused?

IMG_6937.jpeg IMG_6938.jpeg

But I would still like to know what is that chip, and can I get a replacement?
 
At least it's removed now, it won't cause a problem later!
Clean it up good and it will be better in the long run.

It's just a PAL chip with the broken leg, i should have some originals but they are in storage, when i've dug some out i'll send you one!
 
Thanks, that's a good suggestion. I'm still curious to understand how it works with a broken leg though if anyone knows! I have noticed some CPS1 C boards don't even seem to have this chip fitted in the socket.
 
edd_jedi said:
Thanks, that's a good suggestion. I'm still curious to understand how it works with a broken leg though if anyone knows! I have noticed some CPS1 C boards don't even seem to have this chip fitted in the socket.
Click to expand...
It might have some unused harness circuitry?
C boards with kick had two where normal has 1.
 
You must log in or register to reply here.
Back
Top