Pole position.

Lurch666

Lurch666

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Got a pole position that was booting to a ram 8 error.
This was down to a faulty battery backup circuit. The cmosramcs was missing so I bypassed the circuit by shorting the legs of Q2.
This whole section was corroded so I haven't bothered to repair it yet. I'll sort it once the rest of the board is up and running.
pp rambackup.jpg
This got the board booting but with graphics errors:
2026-05-13 10.03.47.jpg

The road was on the side of the screen and the car and road sign sprites are repeated vertically.
Started with the road section and after checking continuity with the 02xx custom at 3N I swapped it with the other 02xx custom at 8N that runs the text (which was fine) but there was no change showing the custom was ok.
pp roadmem.jpg


So I started checking the nearby TTL and found a 283 at 3K with pin 13 stuck to GND. Swapping that out fixed the road. Now I just need to sort the sprites out.
 
Lurch666

Lurch666

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4,208CR
So this other fault with the signs and cars being duplicated vertically is proving more difficult than I thought it might be.
I tried looking in the obvious places but nothing is showing up as obviously wrong. I can't see exactly what part of the video circuit would cause such an error.

So I have decided to start going through the video circuit from start to finish slicing everything I can.
I thought I had a breakthrough with another LS283 at 3C with the pin 10 output stuck high. Replaced it and now there is a signal but no change so the search continues.
 
Lurch666

Lurch666

Active member
Feedback
21 (100%)
Credits
4,208CR
Before I continued searching for a bad TTL I decided to dig(?) out my dig dug board as some of the customs are the same as pole position.
Swapped out all the customs except for the 09XX which appears to be unique to PP. No difference.

So back to methodically testing TTL. there were a few 245s which were showing tiny errors but I've come across this before and it's usually nothing.
After going through everything else I came to the MATCH CIRCUIT. I had ignored this as I had no idea what it's function was. Slicing the 283 at 10M showed missing outputs and other errors.
Should have known:It was a bad 283 that messed up the road,found another bad 283 but replacing that one made no difference so I should have checked all of the other 283s since it looks like they have a higher fail rate than the other components on this board.
Replacing 10M has fixed the issue with the cars and the signs. All graphics now appear good.

Just need to check sound and find out if my sprint 2 steering wheel can be adapted the this game so I can playtest it.
 
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