MVS four slot video noise.

So I have a four slot board I've been restoring, new battery etc. Everything is working perfectly, but I'm noticing some noise on the RGBS signal when I compare it to a single slot board. Any idea what the cause could be? Same supergun, same power supply, same cart, same display. Noise on the four slot, not on the one slot. Thinking it MAY be a grounding issue... there was a green grounding wire on the frame, which I removed since it's not going into a cab.

Any ideas would be appreciated. It's not a very noticeable thing, but it makes my brain itch.

Kujako said:

So I have a four slot board I've been restoring, new battery etc. Everything is working perfectly, but I'm noticing some noise on the RGBS signal when I compare it to a single slot board. Any idea what the cause could be? Same supergun, same power supply, same cart, same display. Noise on the four slot, not on the one slot. Thinking it MAY be a grounding issue... there was a green grounding wire on the frame, which I removed since it's not going into a cab.

Any ideas would be appreciated. It's not a very noticeable thing, but it makes my brain itch.

Click to expand...

Mind sharing pictures or a video?

RyuX said:

Mind sharing pictures or a video?

Click to expand...

Really doesn't show up in a picture.

https://i.imgur.com/xSJ9aaB.jpg

You can kind of see some lighter pixels in the background, they move in a diagonal pattern. Will try to capture a video, but I don't have any way of recording directly from the RGBS output.

So an update... the issue goes away, if I use the YCbCr outputs from the supergun. So it is possible, that the supergun is the issue. It's just weird that it works with the RGBS outputs for the 1FZ board, but not the 4F.

Kujako said:

So an update... the issue goes away, if I use the YCbCr outputs from the supergun. So it is possible, that the supergun is the issue. It's just weird that it works with the RGBS outputs for the 1FZ board, but not the 4F.

Click to expand...

Might be the supergun.. judging from the picture it looks fine to me so it's really hard to say. Do you have any caps on the RGB Lines and do you have a Composite Sync Stabilization Resistor connected to ground ?
I usually run a 680 Ohm Resistor from Composite sync to ground to stabilize the C-Sync and most RGB Cables use 220uF Caps on the RGB Lines as well.

RyuX said:

Might be the supergun.. judging from the picture it looks fine to me so it's really hard to say. Do you have any caps on the RGB Lines and do you have a Composite Sync Stabilization Resistor connected to ground ?
I usually run a 680 Ohm Resistor from Composite sync to ground to stabilize the C-Sync and most RGB Cables use 220uF Caps on the RGB Lines as well.

Click to expand...

As I said, the issue really doesn't show in a picture, it's subtle. I was trying to wire it up to a video recorder, but that's when I saw that the YCbCr signal didn't have the problem.

I honestly don't know how the supergun is wired, it's an aliexpress special. Thinking I'll splice into a JAMMA extension cable I have to pull the RGBS signal out before the supergun and see what I get. Again, it's weird that it's perfect on the 1FZ but I get noise on the 4F. Could also be the RGB upscaler not liking the signal... can try a GBS-8200 I have sitting around instead of the Extron.

Edit: Not seeing the effect on the GBS-8200... so may be something in the signal that the scaler doesn't like. Unfortunately the GBS is kinda useless, as I can't get it to be consistently full screen.