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Author Topic: Pac Man PCB issue  (Read 1019 times)

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CD2193

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Pac Man PCB issue
« on: June 06, 2023, 02:17:00 am »
Since it seems like there's tons of PacMan repair logs out there, figured I'd check to see if anybody has noted this issue before.

During the first intermission, there's a scrolling, dashed yellow line at the very top of the screen that appears when big PacMan chases after Blinky (see pic). No other graphical faults are noted.


lilshawn

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Re: Pac Man PCB issue
« Reply #1 on: June 07, 2023, 10:38:26 am »
if it's just the in the one intermission, and no other graphical glitches are seen elsewhere. I'd suspect a ROM.

CD2193

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Re: Pac Man PCB issue
« Reply #2 on: June 12, 2023, 03:42:43 am »
if it's just the in the one intermission, and no other graphical glitches are seen elsewhere. I'd suspect a ROM.
I'll check to see if all the ROMs are good. Fwiw test mode shows all ROMs are still good.

lilshawn

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Re: Pac Man PCB issue
« Reply #3 on: June 13, 2023, 10:35:49 am »
problem with the RAM/ROM "test" is that it simply checks to see if the data lines are responding, not if the data is good.

you'd have to download the appropriate version dataset for what you have and do a ROM by ROM compare.

...and, unless you have kept a particular old version (for a glitch or something) or have a weird china clone of some kind, you likely might only be able to download the last version and just burn a "new" set of chips.

eliminate that completely as a source of the error.

CD2193

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Re: Pac Man PCB issue
« Reply #4 on: July 09, 2023, 12:35:37 am »
Thanks for the advice! I started pulling the EPROMs to verify them, only to find that the ROM reader that I have isn't compatible with the EPROMs currently on the PCB, so I guess I'll have to get a different reader first

lilshawn

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Re: Pac Man PCB issue
« Reply #5 on: July 09, 2023, 02:16:25 pm »
typically roms are all about the same... you can find a larger one with a generic number and the same pinout that is supported...it will work just fine if you tell your writer software to stop a particular address (the size of the original rom).