Please Help Galaga Experts! Galaga Starfighter Graphics Bassackwards

Madaracs

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Please Help Galaga Experts! Galaga Starfighter Graphics Bassackwards

Can someone help me out? When the Starfighter 'splodes it's explosion graphics are drawn backward! Or rather one side is drawn the same twice.

Take a look at this video and screen shots:



splode1.png


splode2.png


Can anyone tell me which EPROM or which RAM may be suspect? Could it be a bad Zilog? The game does boot up OK otherwise...
 
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I'd start by checking the circuit driving the address pins on the character ROMs.
 
Bump. This is still an issue. I have been swapping parts with other boards trying to figure it out but I haven't managed to luck out. I was reminded of the issue today because I had to fix a RAM problem on it today.

Any advice would be cool.
 
Well I now know not a single custom ROM is at fault. Cleaned and swapped them all last weekend.

I think ChannelManic is probably on to something. Though I don't know where I'd start to find that circuit.
 
Check with a logic probe to see if you have a missing signal on the EPROMs on the video board.

You most likely have a bad socket.
 
OK, will do. That makes sense--if there is no low or high then? Although it could be a stuck low where it should be high or something... but if I don't know which one is supposed to "flip" the explosion graphic it may be tough to find.
 
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