Can someone identify my monitor problem?

[ranma]

Here is the thing, This is the best cab I could get in my country for a
decent price, the monitor (a unknown national brand) was in a very bad
shape, I had to change some color transistors, replaced all the caps, etc.
Now the image is decent, except that it has a lot of background "noise".
I'll post some pictures I could take. The circular lines are not
in the monitor, but some kind of effect from when I took the pictures. What I want you to see are the horizontal lines (or noise). These pictures are taken without any video signal on the monitor, just the raster. But that noise appears the same when the picture is on. The noise has some movement, but the patern is always the same.

Someone, on usenet sugested to move the cab, when I move it the patern changes but the noise is still there. It's not close to any electrical or magnetic field.
BTW, the degaussing coil is not working, but It doesn't appear to be a magnetic problem, or it does?

Well, thats it, if you have any idea of what could be the problem (and a
possible solution) I'll be very grateful.

Francisco

[ranma]

An additional picture

[Ken Layton]

That's the old "Herringbone" (or "worm wiggle") problem. On the switching power supply connect a jumper wire from the FG terminal to one of the GROUND terminals.

[ranma]

That's the old "Herringbone" (or "worm wiggle") problem. On the switching power supply connect a jumper wire from the FG terminal to one of the GROUND terminals.

Can you explain a bit further about this, please?.
There is no specific power suppy with terminals in it. It's just a big circuit board, and one part of it is the power supply. Maybe if you explain what should I look at I can find it. (or any references on the web)
Thank you

Francisco

[Ken Layton]

The problem is not caused by the monitor. The monitor is merely displaying the "noise" it is receiving from the game power supply. It is caused by the lack of good grounding of the game cabinet's switching ower supply.

[ranma]

The problem is not caused by the monitor. The monitor is merely displaying the "noise" it is receiving from the game power supply. It is caused by the lack of good grounding of the game cabinet's switching ower supply.

Oh, but, I'm afraid there is no game power supply in the cab at the moment. The only thing in the cab is the monitor.
Another person suggested me to ground the monitor to another place on the cab. I'm not sure what do they mean, the monitor plug doesn't have the third grounding connector. Is that what they/you mean?
Maybe a loose conection that should go ground in the monitor and is floating?

[ranma]

<BUMP>
I'm so sorry to insist, but I can't find a solution to my problem and I don't know anyware else to ask.
As I said before, I'm sure this is a monitor problem since I don't have anything else running near it, any tips or pointers on were to look for a solution would be very usefull.
If it wasn't for this problem the picture would be very nice.
Thank you.

[Ken Layton]

So you have no power supply and no game board in your cabinet? If that's the case then the monitor is working properly and is displaying noise because there's no signal and no signal ground going to it.

[ranma]

First, thank you Ken.
Ok, now I've narrowed my problem. I took the pictures without signal to be able to see the problem better, but was having the same problem when I had signal too.
Now I've connected my jamma board, and I realize that the noise is gone, however, if I connect my computer back, the noise is there.
So the first part is solved, not a monitor problem  
But do you imagine is that I'm doing wrong?, the image, when I connect to the computer, is very good, but is mounted on that noise, maybe a bad connection or something?