Rainbow Glitch at MVS Bootup

adaup1

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Hi everyone. I should mention this is my first post. I have had a Neo-Geo CD for a long time but recently acquired a consolized MVS, which has just been amazing (up until a few days ago). Recently, no matter which cartridge I put in, I get this coloful checkerboard-like screen. I have noticed that if I let it sit for a couple of minutes, the game eventually starts up. Searching online, I have found a few instances of the same glitch but no clear answer on how to fix it. The whole point of moving to the consolized MVS was to skip the load times of the CD (and of course to access more of the library) but now I have to wait two minutes every time I turn on the system. Thanks everybody!

mvs glitch.jpg
 

adaup1

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AliExpress "cbox"?

Yeah, the fact that you guessed this makes me nervous. I've had it since March with no problems, though.

That said, based off images online, board seems legit.

Voltage issue definitely sounds like it would make the most sense and is what I assumed initially. Nothing seems wrong with the power adapter but I could definitely track down a repalacement and try that. I should mention that without a cartridge in, I get the proper screen immediately. Also, it's not like this is just the case with a multicart or something unofficial. No matter what cart I use I get the same issue.
 
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Carless Walker

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Check for debris in the cart slots too, perhaps a sliver of copper wire, or a ball of solder etc.

Develop thick skin. I'm surprised you've not been flamed into oblivion yet. You may come out unscathed.


Good luck.
 
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madman

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Check for debris in the cart slots too, perhaps a sliver of copper wire, or a ball of solder etc.
Can you explain how debris in the cart slot would fix itself after 2 minutes of being powered on?
 

Carless Walker

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Sure, off the cuff, I was thinking a strand of copper wire (or similar conductor) could create a high-open type situation. Whereas the presence of voltage over time would create a bridge to the a pin, allowing the cart to work.
Alternatively, I could have told him to track down broken traces. This seemed like a good starting point after Xian suggested voltage checks.
 

adaup1

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First thing I did was make sure the carts and slot were clean but thanks for the advice. Only thing I found was dust and barely any at that. I did find this video on youtube from a few years ago with a similar problem. Mentions in the description that it may have had something to do with a trace to the Z80 but it doesn't seem like he found a clear answer or at least I don't understand whether or not he did. I'm not the most knowledgeable about tech side of things. Is anyone able to make anything of this? https://www.youtube.com/watch?v=w4jfOOBCalY
 

Carless Walker

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Maybe someone else more versed will chime in. I've had excellent luck using the search function. It's time consuming reading through thread after thread, and narrowing down your phrasing,but you may learn other things in the process.
 

ack

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First thing I did was make sure the carts and slot were clean but thanks for the advice. Only thing I found was dust and barely any at that. I did find this video on youtube from a few years ago with a similar problem. Mentions in the description that it may have had something to do with a trace to the Z80 but it doesn't seem like he found a clear answer or at least I don't understand whether or not he did. I'm not the most knowledgeable about tech side of things. Is anyone able to make anything of this? https://www.youtube.com/watch?v=w4jfOOBCalY

You should do as Xian Xi suggests the check the voltage. Use a multimeter and verify the 5v rail on the jamma edge is 5v. What you are seeing can happen if the voltage is to low ~4.5v.
 

adaup1

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So I'm afraid voltage does not appear to be the issue, or at least not something I can safely test. The power adapter is outputing propper voltage. I opened up the box to see the board and the board looks super clean but I don't know what I'm looking at, anyway. I'll attach a picture for hahas just in case there's something obviously wrong.Image-1.jpg
 

BIG BEAR

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That's 24.000MHZ Crystal,fuse or bios related.
BB
 
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adaup1

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That's 24.000MHZ Crystal,fuse or bios related.
BB

If that's the case then it sounds like my best bet is to send it off to somebody for repair. I don't want to completely ruin my board by attempting things myself. It looks like there's some people around the forums who can do repairs. I live in the north-eastern U.S. if anyone knows anyone in that general area for the purpose of shipping costs and what not. Thanks everybody for the tips!
 

Xian Xi

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So I'm afraid voltage does not appear to be the issue, or at least not something I can safely test. The power adapter is outputing propper voltage. I opened up the box to see the board and the board looks super clean but I don't know what I'm looking at, anyway. I'll attach a picture for hahas just in case there's something obviously wrong.View attachment 51219

Just from this statement I can tell you didn't test properly. He uses a voltage regulator that converts the PSUs power to 5v so testing the power supply itself isn't really testing the 5v output to the board.

Send it off to someone like Big Bear and also request a legit Unibios upgrade and get rid of the stolen bios on that thing and replace with a legit registered version of Unibios 4.0.
 

GadgetUK

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Seeing garbage like that, and the fact the BIOS has been swapped, makes me wonder if its a bad connection on the BIOS tbh, or a bad connection on the RAM - that looks replaced?

If that area warms up and expands, connection makes - watchdog would likely kick in and boot it.
 
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BIG BEAR

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Is there enough clearance in those units to have the biosmasta installed?? I have a couple on hand.
BB
 
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adaup1

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Just thought I'd hop in to mention that I ended up sending the CMVS to Big Bear who was able to diagnose and fix the problem. While most of the tech is beyond me, from my understanding it was a voltage issue, pimarily invlving the power supply but also a faulty power button. A capacitor would eventually fill with enough voltage to run the unit after enough time but the old power button was extremely sensitive and would easily restart the unit without notice. I want to thank everyone who tipped in with advice, including the advice to send it to Big Bear who did a fantastic job.
 
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