Ms pacman/ galaga 20th reunion arcade monitor has no red, need some help

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Ms pacman/ galaga 20th reunion arcade monitor has no red, need some help

So i bought this nice Ms.PACMAN/Galaga 20th reunion cab in great condition, only one small crack on the right side....the whole game works 100% but the only thing wrong is the monitor, im having some problems with the color red on the monitor, this machine was made in 2000.

basically there is no red, the fruit is black, the 3rd stage is unplayable due to the dots being red and makes me a little annoyed, so if anyone knows whats up or might have an idea let me know. or if your local stop by maybe?

0320011646a.jpg

the red ghost is black in this shot

0320011650b.jpg

umm the dots are suppose to be red in this shot but they are black now which makes the game unplayable

0320011650.jpg

black fruit
 
I have seen two of these that are WG K7400 25" monitors.
 
all i know is that its the original monitor and its the 25 inch monitor...i wont see the machine till saturday so i cant give you guys a full answer, but its stock eveything
 
most likely a K7400, I know that's what ours has.

now I know that all the WG medium res monitors I've encountered have had SHIT tubes (the U5000 and K7500 varieties) the K7400s haven't had tube issues that I've seen.

considering that all of the above mentioned share the same basic design though, I'm inclined to believe that your problem may lie in the neckboard, cause the "tube issues" that I speak of have involved weak or shorted colors, not absent ones.

pop the neckboard off, make notation of the order in which the color bias pots go (if you're looking at the top of the neckboard you'll notice they go in the order of red, then green, then blue from left to right) and the drive transistors go in the same order. in this case, the leftmost transistor will be the one that drives red.

you can try reflowing the solder joints on the transistor, a common problem is that these transistors get so hot that they lift the solder pads/traces, and thus you will observe that you have a contact issue. people have created jumpers from wires, I've personally taken NEW uncut transistors, scraped the coating off traces, and folded the legs over and soldered direct to the trace (the L-shaped elbow of the leg additionally creates a force that holds the lifting trace down once it's soldered in)

you can do some troubleshooting work and attempt to swap the red transistor with the green or blue one, with a stroke of luck you may have had cold solder on the red and you'll find all your primary colors work again. either that, or you'll have red again but be missing green or blue, meaning the red transistor was no good.

that's a good place to start. reflow the transistors first, see if that helps. these monitors are pretty good at "discharging" themselves, so you shouldn't get zapped or anything by pulling the neckboard off. I know it'll be a little difficult to solder with it still attached, due to the funny angle the monitor mounts in the Ms. Pac/Galaga cabinet. if you're really handy you'll know how to remove the neckboard entirely by unplugging the CRT ground, G2 wire and opening the neck socket to remove the focus wire. :)

EDIT: additionally, your red video wire/pin on the JAMMA harness could be messed up too. try the neckboard first, if it's not that, then move on to the JAMMA harness. though I doubt it, it's not like you'll ever be swapping games in and out on these, but it's another failure point to consider. if it's neither of those, expect it to be a bad red gun in the CRT (you'll need a rejuvenator to test this)
 
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reflowing the solder joints

Prairied1ll0 did some work on it today and still the same problem, we also checked the jamma for the red pin and still no red, we tried a different board just to make sure it wasn't the board and same result...no red
 
Yeah I did everything but swap transistors. I didn't ahve any spare parts so I couldn't get it fixed tonight anyways.

Too bad cause it wasn't the easy fix.
 
I wouldn't concede that it wasn't an easy fix if you haven't tried swapping transistors.

just saying.
 
yeah I had tried all of the solder joints but didn't have any parts for this. I'm assuming that it's probably a transistor and I could have confirmed it but there's no way he could have walked away with it working unless I sacrificed one from my own K7400

I actually skimmed the thread and overlooked to check the transistors by swapping.
 
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