Sega Blast City Monitor Grounding Issue

[Kiwi]

Hey there, I'm looking for someone smarter than me for help with a grounding issue I have. I have an MS-2933 monitor in a Blast City and I noticed that there were some volts running through the monitor frame, and whenever I tested it with a multimeter some interference would show up on the screen.

The same thing happens when using the multimeter on this metal plate in the control panel and anything connected to it (such as that bolt on the left). This plate has felt strange to the touch for a while, and I'd like to fix the problem somehow. Any ideas? I already have a 3 prong cord plugged in, and I've swapped cords once to see if it helped, but the problem remained. The house is new so the outlet is definitely properly grounded.

 

[mR_CaESaR]

I've got exactly the same issue.

https://www.arcade-projects.com/threads/blast-city-resurrection.15109/post-308347

Take an AC reading of the ground and metal plate, you will probably get 170V Ac.

Is yours 240v? I found the moment I removed the internal step down, I almost dropped 100v.

I still get around 55v when I prong the same without the internal step down

 

[nem]

None of the Sega cabs have grounded monitors. It's by design. If your chassis is leaking some current (most do), then you will get a voltage reading with a multimeter on the metal plate. The bottom monitor mounts and the metal plate are one thing. It's not a dangerous current.

If you try to ground the monitor, you will possibly get visible interference, like you did when you tested it with the multimeter.

IMO put on some slippers and don't worry about it.

Is yours 240v? I found the moment I removed the internal step down, I almost dropped 100v.

Was the stepdown isolated from the cab floor?

 

[mR_CaESaR]

None of the Sega cabs have grounded monitors. It's by design. If your chassis is leaking some current (most do), then you will get a voltage reading with a multimeter on the metal plate. The bottom monitor mounts and the metal plate are one thing. It's not a dangerous current.

If you try to ground the monitor, you will possibly get visible interference, like you did when you tested it with the multimeter.

IMO put on some slippers and don't worry about it.

For my case, I got zapped when turning on the cab on the front switch or adjusting the monitor - it wasn't a pretty thing, so I needed to find the source of the voltage.

It's worrying when you prong any of the pins on the metal plate (12 way, or 10 way connectors) against the ground, that it was reading 170+V AC.

Was the stepdown isolated from the cab floor?

It's on a wooden board, but wasn't grounded at all. I believe this was OEM

A number of friends I've reached out to seems to have 0v on the metal plate when probing the ground and metal plate (which is what I expect). I've been too scared to touch it again, but I'm not sure if 55V AC will be enough to shock myself - I just want it to get to as close to zero as possible, but I'm currently lost as I cannot for the life of me find where the issue is.