Installed a new PSU, now I've got this weirdness. Any guesses?

[pmindemann]

I purchased a 2-slot MVS cab about three weeks ago, and recently discovered it had a badly frayed power cord. So, I asked the seller (E.C. Amusements outside of Philly) to drop by and replace both the cord and the power supply (just to do both while he was visiting). He came over today and did just that... brand new China-made PSU, along with a newer, non-frayed cable. But then, things started to get weird.

In only have a few games... Bust-A-Move and Neo Turf came with the cab, and I recently got Sam Sho II and a new-old-stock copy of KOF 2002. And while all of the games seemed to play just fine before, now, I'm getting screens that look like this:



And also this:



Sometimes the 1 and 2 player lights flicker, sometimes the screen displays nonsense blocks of color and light. All very weird.

The tech said it was a case of dirty contacts. He told me to lightly sand (using a very, very fine sandpaper) each of the contacts on the games, which I did and then used ispropyl alcohol to clean and remove any loose dust. The tech is long gone, but none of my games play now... even though they all played fine before.

Is this a case of contacts on the mobo suddenly getting dirty and causing things not to work? Is the Chinese PSU causing weird issues? Any thoughts or advice would be appreciated.

 

[Kid Panda]

First thing. Don't use sandpaper on your contacts man.

 

[pmindemann]

First thing. Don't use sandpaper on your contacts man.

Yeah, I thought that was weird, too, but he's had lots of experience with these cabs, so I trusted him on it. Either way, the problem was happening before I tried that, and I only did that on two carts (but the problems persist with all four carts). So, though not good practice, it's clearly not the primary problem. Any other thoughts?

 

[Kid Panda]

I would get a multimeter and check the voltages at the MVS edge, (where the harness plugs into the motherboard), check the 5v line and the 12v line. With the light flickering I would think maybe you're not getting enough on the 5v line. But start there first, does your motherboard still have the original battery on it? If its corroding then some traces may have gotten eaten a bit.

 

[pmindemann]

I would get a multimeter and check the voltages at the MVS edge, (where the harness plugs into the motherboard), check the 5v line and the 12v line. With the light flickering I would think maybe you're not getting enough on the 5v line. But start there first, does your motherboard still have the original battery on it? If its corroding then some traces may have gotten eaten a bit.

Thank you for the advice. I believe it does have the original battery, and I believe I saw some minor corrosion. Can you tell me more about that?

Also, can you (or anyone) describe what you typically see if a cart isn't making good contact? I'd love to rule that out, but the tech said there could be a grounding issue with bad contacts.

 

[Kid Panda]

If you saw corrosion it's time to clip that battery off pronto brotha! I would then clean up the area around the battery, hopefully you haven't gotten much corrosion. And even the littlest crystals you see could cause big damage.

 

[pmindemann]

If you saw corrosion it's time to clip that battery off pronto brotha! I would then clean up the area around the battery, hopefully you haven't gotten much corrosion. And even the littlest crystals you see could cause big damage.

I'm not familiar with the process (perhaps you can point me to a link... if not, I'll do a search). Do you mean literally clip it off and remove it? The corrosion was indeed very minor, and didn't appear to be touching anything else.

One detail I forgot to mention... my CRT (and old RCA model) suddenly developed thick, rolling lines across the screen after the PSU was changed out. It wasn't super terrible, but those rolling bands weren't there before. Another reason I was thinking PSU, but again, the tech thought it was a cart grounding issue. I'm still stumped... and not sure how a corroding battery would have caused that (acknowledging it might soon enough cause other problems).

 

[mr_b]

Yeah that guy doesn't sound like a fucking tech at all.

 

[pmindemann]

Yeah that guy doesn't sound like a fucking tech at all.

Well, maybe not a Neo Geo tech, but he owns and operates an amusement company that buys, restores and sells a lot of arcade cabs (and even build their own), so the guy's not completely unskilled. Either way, the sandpaper bit isn't what's causing the issue, so...

 

[mr_b]

The fact that he just installed and bolted by the reciting of your story is frankly bullshit. He should have dialed in your power supply, did he measure the voltage with a meter while the game was running?

 

[pmindemann]

The fact that he just installed and bolted by the reciting of your story is frankly bullshit. He should have dialed in your power supply, did he measure the voltage with a meter while the game was running?

He was basically doing it as a favor and didn't charge for labor or anything. It semi, kinda seemed like dirty contacts were all that was keeping it from working when he left, so I was ok with that. He's going to come back on Monday, now, so I'm just hoping to be able to help him track down the issue.

When you guys have dirty contacts, what kinds of problems do you see? Does the game not load at all? Do you get issues like the 1 and 2 player lights going whacko? Do you see weird nonsense on the screen? Something else?

 

[dgame]

If all of the games played fine before then it is not likely to be a dirty contact issue. Do you still have the old power supply? As others have mentioned the new power supply probably needs to be tested and adjusted. Do you have a multimeter? Do you want to try to adjust it yourself, or just wait for the guy on Monday?

 

[Xian Xi]

Sounds like your voltage needs to be set. Right now it's probably around 4.5v, up it to 5.00v when you check it with a multimeter and a game inside.

 

[pmindemann]

If all of the games played fine before then it is not likely to be a dirty contact issue. Do you still have the old power supply? As others have mentioned the new power supply probably needs to be tested and adjusted. Do you have a multimeter? Do you want to try to adjust it yourself, or just wait for the guy on Monday?

Thanks for the advice. Unfortunately, the tech didn't have a multimeter with him, so we couldn't check for sure. But there's a little adjustment knob on the back of the PSU that I did try turning up a notch, without really seeing any difference. I was hesitant to turn it up too far, for fear of frying the board. He'll bring a multimeter when he returns.

My only other thought is some kind of grounding issue... like, maybe the tech didn't ground it the same as before, and that's causing the rolling bands on the CRT and the inop mobo. But I don't know much about these things, so it was just a guess.

 

[ReplicaX]

Thanks for the advice. Unfortunately, the tech didn't have a multimeter with him, so we couldn't check for sure. But there's a little adjustment knob on the back of the PSU that I did try turning up a notch, without really seeing any difference. I was hesitant to turn it up too far, for fear of frying the board. He'll bring a multimeter when he returns.

Rule# 1: Never turn a voltage adjust without having a meter on it, period.

 

[pmindemann]

Rule# 1: Never turn a voltage adjust without having a meter on it, period.

Fair enough, but we were desperate and didn't have that tool. So,yes, we did things wrong... we sanded contacts, adjusted the PSU without a meter, etc. All valid to point out as mistakes. But those misjudgments in attempting to fix things weren't the cause of the problem to start with. That's what I'm still trying to figure out, hoping that someone has seen and/or experienced the same kind of weirdness that I described, so we can better diagnose the issue.

 

[ReplicaX]

But those misjudgments in attempting to fix things weren't the cause of the problem to start with. That's what I'm still trying to figure out, hoping that someone has seen and/or experienced the same kind of weirdness that I described, so we can better diagnose the issue.

sigh...

The tech forum is also to teach beginners and even veteran techs how to properly troubleshoot and repair. So they don't hurt themselves, others, or further damage the hardware.

Update us after you have a meter on it and adjusted the voltage properly. We can go further if the issue isn't resolved.

 

[mr_b]

Seriously, you're on a NG forum asking a NG related question. Some of the best tech on the site (Xian Xi, RepX) are telling you its a voltage issue. Holy fuck you didn't even have this issue prior to switching out a power supply and you're still fucking arguing. The garbled screens are very likely due to improper voltage. I mean the damn 1p 2p lights flickering just like lightbulbs will flicker when power changes. I'm beginning to wonder if the light bulb in your skull is flickering

 

[pmindemann]

Seriously, you're on a NG forum asking a NG related question. Some of the best tech on the site (Xian Xi, RepX) are telling you its a voltage issue. Holy fuck you didn't even have this issue prior to switching out a power supply and you're still fucking arguing. The garbled screens are very likely due to improper voltage. I mean the damn 1p 2p lights flickering just like lightbulbs will flicker when power changes. I'm beginning to wonder if the light bulb in your skull is flickering

Didn't meant to offend or frustrate anyone, and I appreciate the advice regarding the voltage. Seems logical, and we'll check that for sure on Monday when the tech comes back out. I wasn't arguing that any of the improper techniques were valid... only that I KNEW they weren't the best, and was trying to move on from that, to find out if anyone had experienced anything similar in regard to what I was seeing on the screen, or the lights flickering, etc. (which no one has replied to, so I'm assuming not). Either way, I appreciate the advice given, and will provide an update once we have proper voltage tests.

 

[pmindemann]

Sounds like your voltage needs to be set. Right now it's probably around 4.5v, up it to 5.00v when you check it with a multimeter and a game inside.

Sorry I missed thanking you for this advice, Xian Xi. Will definitely check it out with a multimeter when the tech comes back.

BTW, love your avatar... I studied Wing Chun Gung Fu myself. Yip Man is... well, the man.

 

[pmindemann]

Panda, dGame, Xian, et al... The consensus was correct. It was a defective power supply. We got a multimeter on it this morning, and it was reading at about 4v (vs. 5), and 10v (vs. 12). Turned out the tech had gotten another bad power supply in the same shipment, which is rare. Either way, we installed a different PSU, and that cured all ills. Everything works great now. Thanks for the advice!

 

[Atro]

have you ajusted the +5V pot ?

Seems pretty much like not getting enough voltage.
turn the machine on without any board ( to prevent damage ) and then tune up to 5V with a multimeter.
After you're set, test again with a board and tune up ( there's always tension loss ) to 5V again and you might
be ready to go.

 

[pmindemann]

have you ajusted the +5V pot ?

Seems pretty much like not getting enough voltage.
turn the machine on without any board ( to prevent damage ) and then tune up to 5V with a multimeter.
After you're set, test again with a board and tune up ( there's always tension loss ) to 5V again and you might
be ready to go.

Thanks, Atro. Not sure you read the post right before yours, but yeah, the original PSU was failing to put out the proper voltage. We swapped it for another PSU, checked the voltages, and were good-to-go.