WG 25K7197 - Color Issues

thegnome

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Ok... I just picked up an UMK3 machine with some monitor issues. Unless you turn the Green Drive Pot all the way up, the machine doesn't display green and with the pot turned up all the way it doesn't display black, but grey-green where black should be. The monitor has not been rebuilt and will be as soon as I can get a cap kit and flyback [there's a hairline crack in the plastic housing of the flyback so I'd rather replace it while replacing everything else].

My question is: What would cause the behavior that is exhibited by this monitor? Could it be a bad Pot/Transistor on the neckboard? Bad Caps? I *really* want this machine to work as soon as I can get it to, because well... I love MK!

I snapped some photos of the boards monitor test screens to help aid in diagnosing the problem, as well as a couple shots of the neckboard and tube.

So here we go...

Test screen menu [you can see the colors are a little out-of-whack]
20130210_144451.jpg


The "RED SCREEN"
20130210_144501.jpg


The "GREEN SCREEN" [You can barely see the slight green tint in the black, it's a little more pronounced in person]
20130210_144509.jpg


The "BLUE SCREEN"
20130210_144519.jpg


The "COLOR BARS" Screen [Notice the lack of green]
20130210_144530.jpg


The "CROSSHATCH PATTERN" Screen
20130210_144540.jpg


Current settings of all the neckboard Pots [From Left: Red CutOff, Red Drive, Green CutOff, Green Drive, Blue CutOff, Blue Drive]
20130210_144943.jpg


Shot of the tube [Shouldn't there be convergence adjustment rings?]
20130210_145004.jpg
 
get it rebuilt that is the first step.

check to see if the pot is broke or dirty.

make sure you have a good green signal coming from the PCB run a continuity test from the PCB to the input connector.

re-flow the video input headers.

check the neck transistor.

Peace
Buffett
 
Do you happen to know what kind of pot/transistor I would need for replacement if these turn out to be poop? I'm having a hard time finding the transistors listed in the WG manual. The pots also don't list what kind they are [I assume they're linear?].
 
i stock many of the parts you would need but i need to know the part #'s printed on each part you need to replace afret determining they are bad.

wells used several diffrent transisters on their neck boards. so the actual Part # you have on there is info i will need.

my bet it it is a lifted pad or broke wire in your harness.

if you can get green on the screen from turning up the pot on the neck board then that means your tube is working because the chassis is driving the gun.

i think your problem may lie between the video header and the PCB.

check that the pins in the jamma harness and in the video conector are making good contact and the wire is not brok anywhere.

Peace
Buffett
 
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