A flag-like waving picture

[Vanderzam]

First of all, since it’s my first post on this forum, greetings everyone!
(I’ve been reading it for more than a year now though. It helped me a lot with my cabinet!)

So, here’s my problem:

I bought a Midway Universal cabinet from a guy I know in my area, containing a Wells Gardner monitor (model 25K7195). The cab was already “ready to use”, with Mame installed and all the necessary stuff (J-Pac, ArcadeVGA card, etc...)

However, I did a lot of work on it, mainly refurbishing the cab itself (painting, etc...) and building a completely new control panel (with more controls).

I noticed while working on it that the picture was slightly “waving” from left to right, like a flag or some slight oscillation. Of course I immediately searched the forum to get some answers or explanations and I found a couple of treats concerning similar problems. From what I understood, the main cause of such waving is bad capacitors.

Since changing caps is out of my league (never done such work before and I’m not familiar with monitors... well not yet!) I first decided to call the guy who sold me the cab, and he gladly accepted to replace the monitor.

So we mounted another one in place in no time (same exact model), hooked everything up and tested it. The waving was still there, same speed, same direction, and same identical oscillation. 

Different monitors, different capacitors, same “flagging” distortion in the picture.
I don’t think the source of the problem is the monitor...

So, what could it be then?

P.S: I also noticed that the waving reduces after the unit is on for a long period. It’s still present, but diminishes a little.

[Kevin Mullins]

Does it have a good ground on it ?

[Vanderzam]

Yes, it is grounded.

I checked the wire (from the chassis to the ground pin) and it seems in perfect condition.

[grantspain]

disconnect the degauss coil from the chassis and remove the marquee light to see if it helps

[Vanderzam]

Thanks for your ideas grantspain.

The marquee light (a simple neon) is not installed.
Still have to buy a new tube. So it can't be the light.

As for the degaussing coil, can you tell me what it looks like and where it is supposed to be connected.

Sorry for asking, but like I mentionned in my post, I'm a newbie with monitors... 

[Kevin Mullins]

The marquee light (a simple neon) is not installed.
Still have to buy a new tube. So it can't be the light.

Is the ballast still wired up though ?
Whether it has a bulb or not.

[grantspain]

also be careful of how close the stepdown transformer is located in relation to the scan coils-if you have one of course

[Vanderzam]

Okay, I'll unplug the ballast and let you know the results.

"...of how close the stepdown transformer is located in relation to the scan coils"

Speaking chinese ?

If I post some pictures of the monitor's back side, would you be able to point me out the "stepdown transformer", the "scan coils" and the "degaussing coil" ?

[lilshawn]

your degauss coil connection should be near the main power input on the board.

it's a big coil of wire that wraps around the big part of the tube...it should only have 2 wires on it.

BUT....

i'm thinking if 2 different monitors do the exact same thing...

it's power - try isolating just the monitor on a single power line and plug the computer in someplace else to try it.
it's interference - from electrical motors, from florescent lights, maybe even from the isolation transformer in the cabinet.
it's ground problem - some computers and accessories are notorious for "ground loops", monitors can back feed noise into amplifiers and create hum...what your basically seeing is hum VISUALLY..trippy

just a process of elimination start pulling things one by one - eventually you will find the culprit

[Kevin Mullins]

try isolating just the monitor on a single power line

Do not confuse that with plugging the monitor straight into the wall or anything like that. The K7000 requires power from an isolation transformer.

[lilshawn]

try isolating just the monitor on a single power line

Do not confuse that with plugging the monitor straight into the wall or anything like that. The K7000 requires power from an isolation transformer.

sorry thats kinda what i meant, musta not come across that way. 

i meant just the monitor plugged into the transformer, if the computer and lights, amp etc, all that stuff is plugged in to that transformer too, it will load it down, and they arent rated for too much power. (only a few 100 watts or something ridiculous like that.) so try plugging everything ELSE into a separate plug.