Tuesday 20 November 2012

Pole Position Repair Log

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.
Color is red is defect somehow. Replacing PROM at 11E for RED 136014-137 (82S129)

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

So I dig out the manual

Table 2-1; Seite 2-2

Checked the EEPROMS
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

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.

Picture of replaced connector edge.

Picture of PROM 11E for RED

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

See the perfect sprites :)

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