Jul 242016
 

Got this board from Muddymusic.
Board was filthy when I got it and most IC legs were a nice shade of green. I decided to clean this up first.
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After a good clean the board came out OK, not great but definitely much better. I noticed that a socketed RAM chip had one of its legs hanging out the side of its socket.
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Not sure what effect this would have but I reseated it properly before powering it up.
I replaced all of the single wipe sockets on this board as I really don’t like them.
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Next up was the power up test and I was greeted with a yellow screen which eventually turned mostly red and stayed that way. I could see the game was booting at least.
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From this point I can be sure the palette circuitry was at fault. Looking at the schematics you can see there are 2 x CXK5856 RAM chips responsible for the palette RAM.
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In my experience these RAM’s have been the most unreliable so I desoldered both of them straight away and both of them failed spectacularly when tested out of circuit.
I replaced them and fired up the game.
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All seems to be working fine now.
Also dumped all the PAL’s from this too and hopefully will be getting them tested soon.