OIB1981
Member
My Ghosts N Goblins board runs fine but every now and then it flashes a color that looks like coin bonus but all over the screen. Anybody have any idea what this could be?
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My Ghosts N Goblins board runs fine but every now and then it flashes a color that looks like coin bonus but all over the screen. Anybody have any idea what this could be?
What you are seeing are glitches in the Scroll RAM area of the board. There are some 74LS245 latches on the CPU board and on the bottom board (I won't say "video board" since a lot of video functions are on the CPU board too!) that send signals back & forth.
These boards are VERY fickle with their timing. I wouldn't touch it until it gets far worse...
Edit: The chips in question were 13F, 14E, and 14F along with the 2k x 8 SRAM (24 pin one) on the bottom board.
Had some spare time today so, I pushed the theory that data is not getting to that PROM and replaced a few more chips.
On the CHARACTER GENERATOR ROM (A-2-7/8), I replaced the two 86 chips @ 9D and 9E, and the 174 chip @ 8E. Tested game. No, change: Game glitches.
On the CHARACTER VIDEO RAM (A-2-6/8), I replaced the three 273 chips @ 8H 9F, and 9H; and the three 157 chips @ 3H, 4H and 5H; and the 32 chip @ 6F; and the 04 chip @ 5F. Tested game. No, change: Game glitches.
On the LINE BUFFER 1 (B-2-5/9) and LINE BUFFER II (B-2-6/9) pages, I replaced four 257 chips @ 6L, 7L, 12L, and 13L; two LS 273 chips @ 6M and 13M; and the LS21 chip @ 14L Tested game. No, change: Game glitches.