Pole position.

[Lurch666]

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.

This got the board booting but with graphics errors:


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.



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.

 

[Mr20to5]

Good luck. Is it an Atari or Namco board set?
I (read we) spent ages and I mean ages chasing ghosts around all the rubbish sockets and corroded legs.

 

[Lurch666]

Atari.

 

[Mr20to5]

Atari.

Double eek!

Check out my write up, on the off chance it helps you out in any way.

 

[Lurch666]

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.