Weird arcade monitor problem.

[Ord]

There is something funny going on with my monitor and i don't know what it is so, i was hoping someone here could help.
Basically what happens is when ever i'm playing shooters and there are loads of flashes going on, the screen around the edge goes all dark. This is especially noticeable when ever i'm playing Armed Police Batrider. The bombs in that game are usually over the top, but whenever i let a bomb loose the screen goes quite a bit darker. Two player is a bloody nightmare.
I've tried degaussing the screen with a degaussing coil and that hasn't seemed to have an effect.
I have a Super neo 29 cab, as pictured below if that is any help.
It's starting to do my nut in!

[raiden]

I know this effect from TV sets, not sure if arcade monitors behave similar. With TVs, it usually means your video signal input level is too high, so the TV´s auto-adjustment kicks in to save the tube from being strained too much. The remedy is adding resistors to the corresponding picture signal wires. With a cab, I´d try to reduce brightness before doing any soldering, but it didn´t help with the TVs that had this problem, because the brightness adjustment is handled after the auto adjustment did its work.
Of course, if you add resistors to the picture lines, a side effect will be that games which worked fine before will look a lttle pale afterwards. That´s why my current setup has customized cables for each PCB, with the fitting resistor strength for each PCB built into the cable. Another way to go about it is using potentiometers instead of resistors. Those can be adjusted manually before the auto-adjustment of the monitor causes problems.
If you´re looking for a quick solution, 150 Ohm resistors are a nice compromise. Sometimes, reducing the voltage sent to the PCB (the adjustable +5V line) can also help.

[system11]

Very common on ageing screens too - but more usually accompanied by the screen size changing with it. As raiden says, dropping the brightness usually helps - I get quite a bit of mileage from adjusting the contrast myself.

[Trevor spencer]

try adjusting the CRT voltage its on the same little white box as the focus . becarefull though that big red wire that goes into the box has a lot of voltage going through it ..

basically the CRT voltage works as a corse brightness control it might just need to be tweaked, DONT TURN IT ALL THE WAY UP this can damage the screen cause its so bright ..

if all else fails email sales@killercabs.com and speak to tony and explain you bought the cab off me (cause its not that old) and see if he can supply a replacement monitor

cheers
Trev