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FIXED!!!!! MVS Repair: Warped PCB repair ideas? (No longer warped, still bad sound)

rewrite

rewrite

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Got in an MVS cart that one of the two boards is pretty warped (the other only slightly). Seems to be warping enough to not make contact in some spots since it's slightly parentheses shaped at this point.

Any way to go about flattening it out?
 
nem said:
I've "fixed" one with hot air. Heat it up, press the middle against the edge of a table so that the board is flexed in the opposite direction (slightly over), and let it cool.

You may have to reflow SMD components afterwards. I didn't.
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That's what I was thinking, but wasn't sure if it was a batty idea. It was that or maybe put a few little blocks in the cart forcing the PCB flat against the other PCB and cart wall.

I'm gonna give it a shot this week and I'll let you know how it goes!
 
How'd the MVS carts board get warped? I thought the boards were held in place with some posts. Correct me if I'm wrong, it's been a while since I've really looked that closely inside an MVS carts.
 
nem said:
Remember to stand your carts upright!
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That's actually a great reminder. I have definitely stored some MVS carts flat in the past. I never even considered the PCBs in there getting warped.
 
Robertguy09 said:
How'd the MVS carts board get warped? I thought the boards were held in place with some posts. Correct me if I'm wrong, it's been a while since I've really looked that closely inside an MVS carts.
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Given how all the chips on this one are poorly reflowed, I think it was hit too hard with a heat gun in its past. I cleaned it all up and checked continuity, PCB seems fine, just doesn't make proper contact now.

I got some REAL bad PCB's years back from Guru that had been stored laying down in a humid shed. Including an M92 where both PCBs touched..
 
oooooooh ouch sounds rough! I hope you got a really good deal at least!
 
Robertguy09 said:
oooooooh ouch sounds rough! I hope you got a really good deal at least!
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Yeah, I wish. lol And that dude is not good to deal with. Bought 3 boards, 2 had issues he didn't mention, all 3 warped like crazy, and I was basically told too bad.

Like any other scummy seller in this hobby, no one mentions these things publicly but soon as you have an issue 14 guys come out of the woodwork going "Oh yeah, that guy's been awful for years, here are these 10 stories".
 
i would use some sort of non conductive spacer in the meantime. you could also lightly bake it in the oven between two sheets of glass...althought i wouldn't do it.
 
Well, heating it up and bending it back went GREAT.

Still have messed up sound though. It's loud garbled roaring over the game sounds real low in the background.

I'm guessing M1 is busted? I've reflowed the SMD stuff, M1, and all 3 sound roms. But since the sound works in the background of the garbled roaring I'm assuming the sound roms are not the issue?
 
SB_Electronics said:
Have you recapped? All that heat would have definitely taken a toll on already aged caps. Also maybe look at replacing the op amps.
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This is not a motherboard issue. It was one of the two cart PCBs that was warped.

I have half a dozen carts and the multi, they all work flawlessly on this 2-slot, and even to double confirm, this cart acts just as bad in my 4-slot and 1-slot.
 
rewrite said:
This is not a motherboard issue. It was one of the two cart PCBs that was warped.

I have half a dozen carts and the multi, they all work flawlessly on this 2-slot, and even to double confirm, this cart acts just as bad in my 4-slot and 1-slot.
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Ah, I misunderstood. Have you reflowed all the solder points including ROM chips?
 
SB_Electronics said:
Ah, I misunderstood. Have you reflowed all the solder points including ROM chips?
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No worries, I was likely not clear enough.

I've reflowed it all! And no progress :/

I'm assuming /something/ is dead or there's a bad trace somewhere or something. But everything I check out seems to check out fine so far...
 
rewrite said:
No worries, I was likely not clear enough.

I've reflowed it all! And no progress :/

I'm assuming /something/ is dead or there's a bad trace somewhere or something. But everything I check out seems to check out fine so far...
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Nah, you were clear. I just can’t read 🥴. I’m assuming everything has continuity from edge connector to chips? Has the edge connector been cleaned?

I would check the ROMS for bad bits as you are getting good background sound but bad sound fx.
 
SB_Electronics said:
Nah, you were clear. I just can’t read 🥴. I’m assuming everything has continuity from edge connector to chips? Has the edge connector been cleaned?

I would check the ROMS for bad bits as you are getting good background sound but bad sound fx.
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Yes and yes.

That's what I'll do next then. Thanks for the suggestions.
 
I bought a box full of 50 or so "non working" MVS carts a while back. After going through them all about 75% of them worked but had sound like this (they were almost all KOF97 for some reason also).

Anyway I fixed a bunch of them and the culprit was the PCM chip on the PROG board:
https://wiki.neogeodev.org/index.php?title=PCM

aside from the ROMs and the PCM chip the only other chip that handles audio is the little CMZ chip on the CHA board
https://wiki.neogeodev.org/index.php?title=File:Crt_zmc.jpg

Depending on your specific game's V-ROM configuration there may be some logic chips doing some bank switching on the PROG board but those are less likely to fail than the PCM and ZMC in my experience.
 
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