Omega, Neo Geo MVS - Garbled Graphics

[philexile]

Hello,

I'm having some issues with my Omega MVS, and it recently developed this issue with garbled graphics and text when booting the NeoSD (which is the only cart I have to test with at the moment):






I've had this Omega since 2014 so I thought it would be a good idea to check the caps. There were a number of bad ones – the two 470uf caps in particular had very high ESR and one was well over 50 ohm.

It looked like the MVS board itself was never recapped, which surprised me since this is an Omega, and I thought that was part of the deal. The battery looks to be original as well.

In any case, replacing the caps didn't resolve the issue. I tried many things including the following:

1. cleaning the cartridge contacts (and NeoSD contacts) with deoxit
2. updating (and verifying) the unibios to 4.0 (the original chip had 3.1)
3. checked all the traces on the capacitors
4. ran the diagnostic bios – all tests passed for whatever that is worth
5. cleaned and reseated the unibios chip

At this point, I'm out of ideas and the only possibilities for me would be:

1. The Neo Bios Masta install is a faulty install. I noted the hot glue, and I've heard that can sometimes cause issues over time, see below:



2. Maybe a faulty RAM chip?

In any case, I figured someone here would have more experience with MVS systems and could point me to a solution. I reached out to Shadow (the creator of the Omega), but I haven't heard back from him.

Thank you

[SavagePencil]

You've got a least significant bit stuck low, which is why Es are turning to Ds, Ss to Rs, etc. If you flex/jiggle the board, do you see any screen changes?

[philexile]

Hello, I’ve tried to wiggle the cartridge itself while the unit is powered up, but there weren’t any changes.

Is there another area that I should be flexing the board at?

Thank you

[bobrocks95]

I am not sure where to source them, but since you have a socketed BIOS with the NeoBIOSMasta I believe you can put a diagnostic BIOS in that will run some good hardware checks. At least, that's how the person I sent my broken CMVS to determined that I had a fried CPU.

Or maybe the Unibios has something like that built in already?

[philexile]

Hello,

I did try the Diagnostic BIOS and the tests all passed. I'm not sure how thorough that test is, as it was completed in seconds upon booting the console.

Any other ideas?

Thanks again

[Josh128]

Your OMEGA should use an MV-1C mainboard , I assume. *EDIT - I just confirmed it from your pics.

I had a Neo Geo MVS MV-1C with similar issues-- check these pics of my issue.




Your issue is most likely caused by a bad solder joint or broken trace coming from the cartridge connector. These garbled graphics can sometimes come from bad CROM joints or traces on carts, but since your NEO SD is a brand new device that functions differently from carts, I think it can safely be ruled out. Its also very unlikely you have a RAM or graphics RAM IC issue on your MVS. As mentioned above, slightly flexing the cartridge front to back while its displaying these garbled graphics may temporarily change or resolve it-- this points to bad cart connector solder joints or broken PCB traces at those joints.

What happens when you boot with no cart? Are garbled graphics present like that too? Do you get the crosshatch? Crosshatch means all RAM tests passed. Also, if you press buttons on the controller, it should take you to the system setup screens. Are the garbled graphics present in any of them?

I recommend re-flowing ALL the the solder joints on cart connector (on the underside of the MVS mainboard). There are a SHIT LOAD of them, it will take a little while. Doing so completely fixed the problem I had on mine. Also, if that doesnt fix it outright, you will need to follow the traces from those solder joints to their next destination on the main board and examine any of them for damage, using a magnifying glass, and proceed to reflow them at their next joints.

Below is some info about the issue, but again, since you dont have a cart and still get the issues, its 99% a bad trace or solder joint.

https://wiki.neogeodev.org/index.php?ti ... c_glitches

[Taiyaki]

I second that, I think bad solder joint too. I've had this happen on individual games (not the system though), and that was the fix.

[Josh128]

OP, any update??

[philexile]

Hello,

Yes, and sorry for the delay – it is a very busy time at work. Here is what I tried:

• Cleaned the cartridge slot (99.99% isopropyl, also deoxit)
• Replaced the capacitors – one was very bad (50 ESR)
• Replaced the battery while I was in there – it now has a “clip”
• Reflowed the solder on the cartridge slot pins
• Updated the unibios to 4.0 (free) from 3.1
• Ran the diagnostic rom – all passed
• Reseated the unibios adapter (also removed the hot glue)
• Double-checked each of the unibios adapter solder points
• I looked over the board for any broken traces for a while, no luck

The graphical glitches only happen when a game is inserted. The unit can boot/self-test without any issues.

I heard back from Shadow who is going to refurb the Omega completely to get it back up and running. I'll be mailing it to him this week and will let you know what I hear from him in regards to what the issue is. Personally, I'm stumped – which I find very annoying, but sometimes you have to call it a day!

Thanks again for everyone's suggestions.

[Josh128]

Well, you did your due diligence, for sure. Glad the seller is going to repair / make right for you!