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Another Ground Noise Post - Super Neo 29 Type II

notsonic

notsonic

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I have a Super Neo 29 Type II with the original monitor. It has the LCD marquee and the big link board.

The cabinet used to shock the shit out of me because it's all metal. I've since added a 3 prong power cord, tying the cabinet ground to earth. I'm going to double check but I'm pretty sure this has introduced shadowy wiggly interference most obvious in darker green stuff.

Anyone ever try to address this with this cabinet? I don't think it's possible to isolate the monitor from the frame ground so I guess the next step is to try tying earth and logic ground together if they aren't already.


Edit: it looks like logic ground and earth are already tied together somewhere. If I take the link board out of the equation it's not as bad but it's still there. It's really not that bad to begin with.

Anyone ever tried like a power conditioner or something to clean up the power in their house?
 
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So I took a deeper look in the cabinet. All the cabinet earts are tied together at the exterior earth stud, which is where I have the ground from my 3 prong cable.

The stud is on a metal box which is attached to the metal body of the cabinet. There's actually no continuity between the box and the rest of the cabinet due to the powder coating.

There are 4 earths. Ones goes to the ac line filter housing, and the other 3 go into the power supply. From the power supply there's a handful of green wires but I think only one is an earth (based on the gauge) and it goes to the coin slot in the control panel. Earth makes continuity with the rest of the metal in the cabinet through the body of the power supply.

The monitor has no explicit earth, it has a two prong power cord that plugs into an outlet on the power supply.

Basically unless the powder coating is supposed to be relied on to be an electrical insulator, all the metal in the cabinet is continuous which includes the monitor frame, so there's no way to not ground it unless nothing is grounded.
 
Remove the grounds from the PSU body and monitor frame to test and see if it solves your problem (won't hurt anything to test for a bit). If it solves the problem, come up with a grounding solution that does not ground those parts.

I run all my cabs with these parts ungrounded (I get interference otherwise) and have no problems. You may need to build some cables to manually ground the parts like the CP if it is all continuous (run ground from the metal box to the individual part)

FYI it's actually considered not ideal to daisy chain earths like they are in your cab. Each grounded part should have its own direct line to the main earth hub at the rear. At least that's what I've been taught.

EDIT: Also failed continuity test != infinite resistance. Your cab body is grounded well enough I'm sure, unless some crazy dielectric paint was used
 
FWIW all the wiring is original when compared with the diagram in the manual. The metal parts of the cabinet are grounded through each other either via the earth stud or the power supply body. Earth is connected to the power supply from the AC input connector. It's not just a ring terminal on a screw.

Also, the only thing that could really be considered daisy chained is the coin slot.

The point I'm trying to make is nothing metallic on the cabinet can be earthed without also earthing the monitor, and long term, I'd rather deal with some faint interference on dim solid colored screens than get zapped. Every time I touch this cabinet I still reflexively pull away with how many times it's shocked me before grounding it. I think the only way to do it would be to insulate the monitor frame around the mounting points (I think the Net City does this) and also dig into the power supply to see where earth is being tied to logic ground.

The biggest reason I wanted to unground the monitor was so I could use a Jamma VS harness on it with my Astro City.
 
Yeah most cabs should have the monitor totally isolated from earth ground. I'm kinda surprised that the cab came from the factory with the monitor frame grounded since I'm pretty sure that should always be floating, otherwise there's a potential difference with the video signal ground. Tying DC ground to earth ground should mitigate this, but the connection between earth ground and logic ground in your PSU may actually need to be beefed up rather than eliminated. I have removed interference with screw terminal PSUs where there is already continuity between the two, by adding an 18AWG wire directly betwenn earth and DC ground, rather than relying on the internal connection.

Can you share some photos of the PSU and ground wiring?

EDIT: In metal cabs there's usually these plastic standoffs around the monitor frame mounting points like you've seen in Net City. Same thing in my Aero and I believe in my MVS U4
 
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I'll pull out the psu and take a look at how the earths are routed.

Pulling the front bezel off is really annoying but I can do that and see if it looks like any kind of isolators are missing.
 
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