Galaga missing Red

wrkey

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Dec 13, 2009
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Spring, Texas
Been working on my Galaga for a while now... it was working fine and the color was as it should be. It died on me ... CPU wise... and I've been working and swapping various things trying to get it going again. It would never get to the 'Boom'.

I now have managed to get it working and can play a game on it. However, it's missing the red pixels in the game. The red in the Starfields are showing up... just no the reds in the game itself. So I don't think it's a monitor issue... but could be wrong obviously.

I am assuming that A) the star field is generated seperately from the game graphics and B) since I see 'red stars' this would indicate the red on the video tube is working.

If this assumption above is valid, then my 'red problem' lies someone where in the CPU process and/or data communications between the CPU and the video board.

Please know that I really have VERY LITTLE experience here and most of what I do is guessing. I do have spare boards and chips as I've picked up a complete second machine with trashed cabinet and a set of 'untested' boards. So.. I can swap chips if necessary to try to make it work. However... since I've broken legs on at least two chips thus far... I would rather make a 'educated' swap rather than a 'blind' one.

So.. someone educate me please... where should I start looking first. I have only a basic Digital Multi-Meter at my disposal so if there is something I can check with that.. let me know.

Any assistance would be extremely helpful!

Thanks,

Rusty
 
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