Punch-Out: corrupted graphics/colors on upper monitor

MaximRecoil

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Punch-Out: corrupted graphics/colors on upper monitor



Everything is fine on the lower monitor. For the upper monitor, the title screen is fine, but the high score screen and the fight status screen have corrupted graphics/colors, as well as some random lines that flash on the screen. I've confirmed that the problem is on the BAK board. I've also confirmed that the color proms are all good.
 
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I don't know if this is the exact problem, but there's 2 color PROMs on the board, one for each monitor I'm assuming. this is probably a common enough problem that it's probably that.

hopefully someone else who knows better can chime in.
 
There are six color proms on a Punch-Out boardset (3 for each monitor), and Punch-Out is notorious for chewing them up, but like I said, I confirmed that all of the color proms were good.

In any case, it's now fixed, though I have no idea how. Since I knew the problem was somewhere on the BAK board, and I'd already swapped the color proms around with my other Punch-Out boardset to confirm they were good, I tried swapping the only other socketed chips on the BAK board around, which are four EPROM chips (part of the overall ROM set). Now both boardsets work. Normally I would think that means one or more of the EPROMs simply needed to be reseated, but I reseated all of the socketed chips on both Punch-Out boardsets the day before yesterday when I first noticed the problem (and on my Super Punch-Out boardset too, while I was at it).
 
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