Newbie needing help with wiring grounds.

[Necrobot20XX]

I have a Neo Geo MVS 1 slot. My monitor sometimes shows wiggling visual noise. I researched a lot and found a quote in a few places from Ken Layton that said this.

"If the pattern is "herringbone" (as the experts call it) which newbies would call a fine "worm wiggle" you need to connect a jumper wire on your power supply between the "Frame Ground" terminal and the DC output Ground terminal."

The problem is that I have no idea what the frame ground and DC output ground terminals are. Can someone please help, I'm more of a visual learner. I am including pictures of my power supply.

[big10p]

Can't see the terminals in the top pic of your PSU, but you should have one marked FG or with a ground symbol. This is where the earth wire coming from your mains supply is attached. You should also have one or two terminals marked GND or COM. The info you've been given seems to say you should put a bridging wire between these.

The bottom pic is the iso transformer for the monitor and is unrelated.

[Necrobot20XX]

There are three different sets of wires coming off my PSU. I can take more pics if this will help someone help me.

[behrmr]

It is likely that your PSU is frame grounded internally so you can just back off a screw in the housing and use that.  Then your PSU's ground would be one of the black wires coming off of an outlet.  Test it with a meter to be sure.

[Necrobot20XX]

The PSU has a power cord that plugs into the back from the outlet. So do I need to ground that to the internal grounds? I think I'd have to open the PSU to do that, or am I wrong?

[MTPPC]

The PSU has a power cord that plugs into the back from the outlet. So do I need to ground that to the internal grounds? I think I'd have to open the PSU to do that, or am I wrong?

Measure the resistance between the black wire and the case of the PSU. If zero, field ground can be found on the PSU's metal case.

Ken's advice is for switchers that have a row of screw terminals.

[Necrobot20XX]

Well that stinks. The herringbone pattern wasn't always there. It seemed to come and go as I was tinkering with things when I got it and cleaned it up. It also seemed to come and go when I moved it around the house. Now that we bought a house it has a permanent spot but the herringbone thing is back. Anyone know how to fix it with this kind of power supply? Also, sometimes my multicart resets on some games, which I read was possibly a voltage problem. My friends machines, which have the screw terminals, also have adjustable voltage, but mine doesn't as far as I know. Although the games stop resetting once the machine has been on around 30 minutes and has "warmed up".

[big10p]

It's always a good idea to check voltages. You'll need to buy/borrow a multimeter for this.

Also, if the problem is intermittent, you may have a dodgy ground connection somewhere. Is the monitor image affected by wiggling the power cable plug, where it plugs into the cab?

Another possible cause could be the capacitors on the monitor chassis gone bad. They don't last forever.

[Necrobot20XX]

I have a multimeter but I'm not sure what I'm doing. I had my wife watch the monitor while I checked all of the grounds in the cabinet but couldn't make it better. Wiggling the power cable did nothing and I even checked with another cable I had around. Is there any way to know if it's the capacitors without replacing them? I also noticed a new pro lem since I've been trying to fix this the wiggle noise problem. The monitor has a noticeable vertically scrolling line that's brighter that the rest of the screen. It reminds me of when you try to record a crt with a camera and can see the electron beam scanning the image on the tube.

[Necrobot20XX]

I tried every trick I could find online, would my power supply be going bad? The noise is there no matter what and with all the tinkering I've done it seems to look even worse now. Maybe it's noise from the power outlet, but I only have surge protectors to see if that helped, but no such luck. This is only a new thing that's gotten worse since I moved to our new house. I'm pulling my hair out trying to fix it but it's so hard to find my exact problem searching online not to mention a solution.

[big10p]

OK, I've done up a couple of pics to show you how to test the voltages. I've included -5v but don't think MVS uses that.

With the cab on, place the black lead probe on GND and hold it there. Now you can test each voltage by placing the red probe on the contacts indicated.

[Necrobot20XX]

Thank you so much. I tested it and ask of the voltages read way low. Does that mean I need a new power supply?

[Necrobot20XX]

So when i checked the readings I unplugged the jamma harness and read from that. Now I plugged the harness back in and the game won't come on. The LED on the board isn't lighting up. What did I do wrong?

[big10p]

You need to check the voltages with the harness connected to the board, else you'll get wrong readings. The PSU can't regulate properly without a load on the +5v rail. Make sure you've plugged the connector back the right way! There's a 'parts' side and a 'solder' side.

[Necrobot20XX]

Crap. I didn't know. Now it won't come on but the monitor and maquee light still work.

[big10p]

Did you plug it in upside down, then? 

[Necrobot20XX]

It's plugged in right, there's no way to plug it in backwards because of how its made and the way the wires are in the cabinet it doesn't have enough room to be plugged in wrong.

[big10p]

Can't think why it's not powering up, then. Make sure the edge connector is fully pushed on. Think your PSU may have had it, but try checking voltages again (with board connected) and post them here.

[Necrobot20XX]

The readings were 0 on the grounds, 0.58 on the +5v, 0 on the -5v, and 0.24 on the +12v.

[big10p]

You don't need to test between the 2 grounds. I just indicated in the pic that there are 2 ground contacts, and 2 +5v contacts.

Anyway, the readings are super low - even without a load on the +5v rail. Sounds to me like the PSU has had it, unless someone else can suggest something? There's no voltage regulator knob on your PSU, right?

Your marquee and monitor still work because they aren't powered from the JAMMA PSU.

[Necrobot20XX]

There's no voltage regulator. But the same power supply powers the whole thing, monitor, marquee light, and the PCB, unless I just don't understand how it works exactly. Before I checked the voltage by unplugging the JAMMA harness everything worked, besides the visual noise I was trying to get rid of. Now the PCB seems to not be working and the LED won't even come on. So hopefully this is just a PSU problem and the PCB isn't messed up, right?

[big10p]

The monitor iso transformer and marquee ballast take a mains voltage, so your PSU will just have a pass-through connection to these, probably. The +5v, -5v and +12v are provided and regulated by the PSU.

Since it's not possible on your cab to plug the edge connector in upside down, the board should be fine. That is unless the board was the cause of the fault in the first place, and it's finally packed in.

Do you have (or can borrow) another JAMMA game board to test with?

[Necrobot20XX]

I could, but since the Neo Geo needs an adapter for true JAMMA, I'd need to buy an adapter first. Basically, the Neo Geo has stereo sound while most machines have mono, it's wired slightly different and can potentially cause damage over time, but the adapter fixes that. I'd say that I need a new PSU  at this point. I'm just confused as to why the board stopped coming on after checking the voltage wrong. When I did it, I used the connectors on the harness and didn't touch the PCB until I plugged it back in. I hate it because the power supply I need for my Neo Geo is about $40 plus shipping.

[big10p]

Yeah, that's why I suggested testing with another board first, to make sure the PSU is at fault.

I'm pretty sure 1 slot MVS boards are standard JAMMA wired, so you can just plug a JAMMA game board right in. The pic I posted above even has JAMMA written near the connector. Only the multi slot boards need an adapter, I think.

[Necrobot20XX]

I'll do some research to make sure. I'd have to borrow a PCB from a friend and don't want to ruin his stuff.

[big10p]

For sure. You just want to test with a common, cheap board - nothing rare/valuable.

I *think* I might know why your board doesn't power up after testing the voltages: powering up a switching PSU with no load on the +5v rail (i.e. no game board attached) causes it to not be able to regulate the voltages properly. I expect this puts extra stress on the PSU components, which may have been the final nail in the coffin for a PSU already on it's way out.

[Necrobot20XX]

I think I'll just be ordering a new PSU in the next few days. Hopefully this will fix the noise in my monitor and the resetting games on that Multicart. I appreciate all the help, it's been a learning process ever since I got my Neo Geo, which is my first cabinet. I will post an update here when I get a new PSU to let you know.