ATTN: Wells Gardner D9200 owners

[Dan Gendreau]

I've been having problems with slightly discolored patches on my Wells Gardner D9200 monitor  pretty much since I bought it a year ago, but the problem was recently solved with the help of WG tech support. I thought I would let you all know since I think many other D9200 owners could potentially run into the same issue.

I kept thinking the screen was getting magnetized some how and needed degausing, but no matter how often I degaused the discoloration kept reappearing now and again and in different places on the screen.

A little background on monitor masks: The D9200 has a metal screen just inside the tube called a shadow mask. It is used to direct the 3 electron beams at the proper colored phosphors on the inside surface of the CRT.

Apparently when you have large areas of extremely high contrast video (ie large white squares on a black background or vice versa) for long periods of time, the shadow mask can become slightly warped. The mask returns to its correct shape a few minutes after the extreme contrast is gone, but when the mask is warped in certain areas (where the high contrast was) the beams bleed over into adjacent colors causing discoloration.

In my case, the high contrast culprit was the standard windows color scheme (but with a black desktop). Whenever I left my cabinet at the mame32 screen for a 15 minutes or more the distortion would appear for a few minutes after entering a game.


The fix was to change the windows color scheme to dark gray window frames(3d objects=96,96,96),  black text on a gray background(window=128,128,128). The UI is still clearly readable, but not so glaring anymore. I'm sure other colors are fine, but try to stay away from large patches of white.

Mame32 users note: Mame32 doesnt properly respond to the WM_SYSCOLORCHANGE message, so you will need to exit and re-enter mame32 once after changing the color scheme.

I dont consider this issue to be a flaw in the monitor's design and I would still recommend it to anyone building a cabinet. Its just something that you ought to be aware of. Especially since the cause and fix are not very obvious (at least to me).

-Dan G.

[Dan Gendreau]

heh, i guess the smilie engine ate a little bit of my post there. That should have read:

(window=128,128,128)

[Carsten Carlos]

Most likely this happens when you set your contrast-knob very high - the same problems occure with some TV's when contrast is near maximum and you are watching wintersports or anything else white for some time. Maybe setting contrast lower and brightness-control higher instead would help either!