Post a Comment On: Arcade and Video Game Modding

Okay, the Pole Position PCB is again on my desk. As told it has some issues for the graphic output. This was the starting point.
[Image] Color is red is defect somehow. Replacing PROM at 11E for RED 136014-137 (82S129)

[Image] After that fix the picture still has some issues. Every second line is missing on the sprites.

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[Image] So I dig out the manual

Table 2-1; Seite 2-2
http://www.arcade-museum.com/manuals.../P/polepos.pdf


Checked the EEPROMS
http://www.solvalou.com/subpage/arcade_roms/P/polepos1
13N and 12N are 2764, 8 * 8Kbit (small cars and signs) OK
6N (background) und 11N (All Cars and signs) sind 2732 8 * 4 Kbit OK

Then I found this info
http://forums.arcade-museum.com/showthread.php?t=61451

I checked schematic 15A Motion Object Line Buffer. Control Logic for Lines is in 74S158@8D (control logic) and the lines are recombines in 74S298 (recombines lines). Line Buffer is needed in SRAM 2148L-2 @ 9F, 10F.

9F and 10F are 55ns RAM; 137199-00, used 2149 ones.

After replacing the SRAM the PCB was fine again.

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Picture of replaced connector edge.

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Picture of PROM 11E for RED

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[Image] Replaced SRAM on 9f and 10F. Each replaced IC gets a new socket.

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See the perfect sprites :)