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MV1C Issues - Random Reset, Exploded Cap (!) After Recap

kazuo

kazuo

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Hey everyone,

Looks like I somehow ended up with the MV1C from hell. Had this thing for years, and it only recently began exhibiting problems:
  1. Random resets. To be clear, the random resets were happening before I attempted the recap. This seems to happen more frequently when using flash carts, but also happens with original MVS carts as well. This is on a JAMMA cabinet with a brand new Mean Well PSU; no other (non-MVS) boards exhibit this issue, so I'm inclined to believe it's specific to the MVS board. All hardware tests pass. Voltage is 5.01V at the JAMMA edge. I've tried going as high as 5.1 and as low as 4.99 and it doesn't make any difference. It'll reset after a few minutes or some other random interval.
    1. I read in a few places that this may be a RAM-related problem; inspecting the RAM chips didn't reveal anything obvious, but I did notice one of the chips (RAM6) appears to be missing part of a pad on one of the legs (!). I probed the leg with tweezers, and it's not moving, so I'm inclined to think this isn't the problem, but happy to pursue further if people feel otherwise.
  2. Exploded cap following a recap. The specific cap is AC5; it blew up right after I powered the cab on. I got the cap kit from Console5. Check the images below. The board still boots fine and will run carts, but the colors and brightness are all messed up.
    1. Did I short something? Used the wrong cap? Or just bad luck and happened to get a bad cap?
RAM6 chip:
cy3uydqm.jpg

https://i.imgur.com/cy3uydq.jpg

Exploded capacitor (AC5):
l9cEapLm.jpg

https://i.imgur.com/l9cEapL.jpg

Bottom of exploded cap:
xckpOWWm.jpg

https://i.imgur.com/xckpOWW.jpg

Appreciate any help. Would love to get this all in working order again.
 
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Hard to see from photos but is it possible you reversed polarity on the capacitor? That would be my guess as to why the cap exploded.

Also, it looks like the heatsink is missing. I don’t think that would be the source of your issues but it may point to previous modifications which may be causing the random resets.
 
Ugh, yeah, I think you're right. Seems like I flipped the polarities on the caps. This is what I get for doing things like this at 2AM and not checking my work after I wake up... going to go and fix that now. Any chance I caused any other damage as a result of this? I tried some other boards on my cab and I do feel like the image might be a little dimmer... wondering if I may have accidentally overdriven the monitor chassis somehow as a result of flipping the caps. I believe it's an MS8 but it's been a while since I looked back there.

The heatsink was missing when I got it; I don't see any other obvious modifications beyond that, but if anyone is aware of anything I should look out for, let me know.

Thanks for the tips!
 
kazuo said:
Any chance I caused any other damage as a result of this?
Click to expand...
I don’t think reversing the caps would damage the monitor but I leave it to someone more knowledgeable than me to weigh in.
 
Reinstalled the caps in the correct polarity; replaced all of the 470uF caps with the originals and tested the board. Seems to work okay now, but I did have to adjust up the monitor brightness (which is a little odd since it was fine before this). Sound, controls, video etc. seems fine. I've been letting it run in attract mode for about an hour now and all seems well. No random resets (yet!), but I'll keep an eye on that.

I tried reflowing that leg on RAM6 just to add some fresh solder and try to strengthen the joint. No idea if it did anything. If anyone knows where that leg/pad connects to, I think I might just run a jumper to the other end to rule it out as a potential cause of the reset issue.
 
The capacitors smooth out power so it may be that the old capacitors were faulty leading to random resets.

Glad it’s working now.
 
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@KOarcade Doesn't sound quite the same unless I misunderstood your post. I don't get any green screens or garbage, I just get random resets during gameplay. Most common issue that I was able to identify by searching online was a problem with one of the RAM chips; I wasn't able to identify any obvious issues with RAM on my board beyond that ripped pad I found, but after I recapped and reflowed, the problem seems to have gone away... I also cleaned the cart connector with Deoxit, but I doubt that had any meaningful effect.
 
If AC5 is the one above the other 2, that’s the filtering cap for the 12v line.

As for random resets, download and run the Neo Diagnostics bios from smkdan and test all the ram on the board. Usually random resets via RAM would be the fast video RAM which on the MV1C is internal to the GRZ. I didn’t look but pin6 might be D0 on the VRAM but that won’t cause resets, just graphical issues only.
 
Awesome, thanks Xian! Appreciate you taking the time to chime in with your endless expertise on all things Neo. Yes, AC5 is the one above the other two, the one that's blown with the little thread things hanging out of it. I've since gotten a new set of replacement caps; I've been running the old ones in that area temporarily without any issues.

Any idea if the Diagnostics BIOS can be used on Flash Carts, e.g. NeoSD/Darksoft? I tried looking around for something that would run on NeoSD, but didn't have much luck. Not sure how to use the Neo Builder to make a .neo (or if that's even possible).
 
I’m not too educated on the DS or NeoSD carts but if you are able to upload a bios file on them then you should be able to do it with the Diagnostic bios as well.
 
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