So after fixing a pole position I decided to do another one. Since I now had working boards how hard could it be?
At first it was not booting which was solved by replacing the pal with a gal at 7C.
Then it booted to a ram 6 error which was solved by replacing the ram at 7J.
Now it booted to a ram 0 error. This was fixed by replacing the 2114 at 8F on the video board.
Then it gave a ram 30 which was the ram at 3E so I replaced that.
Now the game was booting but with messed up graphics which were smeared across the screen. While looking for that fault (which turned out to be a bad LS174 at 8L on the video board) it started to boot to a ram 28 error which is the ram at 3F.
So I replaced the ram at 3F on the video board but that's made no difference.
I have checked continuity for the ram chips and checked all the logic in the video sync chain,control signal converter,video ram address controllers and the playfield video memory. I can't see any other part of the video circuit that could affect this ram. If I plug in my good video board the game boots so it's not an issue with the CPU board. I've cleaned the edge connectors,checked voltages and swapped out all the custom chips.
I'm really running out of ideas now. Can anyone suggest where to look?
It's annoying because I fixed the graphics issue but this ram 28 error is stopping me from seeing if the graphics are fully fixed.
At first it was not booting which was solved by replacing the pal with a gal at 7C.
Then it booted to a ram 6 error which was solved by replacing the ram at 7J.
Now it booted to a ram 0 error. This was fixed by replacing the 2114 at 8F on the video board.
Then it gave a ram 30 which was the ram at 3E so I replaced that.
Now the game was booting but with messed up graphics which were smeared across the screen. While looking for that fault (which turned out to be a bad LS174 at 8L on the video board) it started to boot to a ram 28 error which is the ram at 3F.
So I replaced the ram at 3F on the video board but that's made no difference.
I have checked continuity for the ram chips and checked all the logic in the video sync chain,control signal converter,video ram address controllers and the playfield video memory. I can't see any other part of the video circuit that could affect this ram. If I plug in my good video board the game boots so it's not an issue with the CPU board. I've cleaned the edge connectors,checked voltages and swapped out all the custom chips.
I'm really running out of ideas now. Can anyone suggest where to look?
It's annoying because I fixed the graphics issue but this ram 28 error is stopping me from seeing if the graphics are fully fixed.