It had also been stored in a damp place so it had some corrosion and every socket on the board needed to be replaced, a lot were single wipe rubbish that would have to be replaced anyway. Apparently Atari made these boards or at least assembled them, I'm not sure if this is true but it would explain the sockets.
This board uses a LOT of PLDs (Programmable logic devices), all secured and none have been dumped or replicated from what I can tell. This was my main concern as one bad PLD and I wouldn't be able to get it going.
Top Board PLDs
Location Device Name
U9 PAL20L10 38-01
U42 PAL16R6 37-01
U43 PAL16R4 36-01
U44 PAL16L8 35-01 - Bruteforced, jed file available at wiki.pldarchive.co.uk.
U54 PAL16L8 41-02 - Bruteforced, jed file available at wiki.pldarchive.co.uk.
U55 PAL18P8 39-01
U68 PAL18P8 40-01
U74 PAL16R6 19-01
U75 PAL16R6 18-01
U82 PAL16R6 21-01
Bottom Board PLDs
Location Device Name
U16 PAL16L8 03-01 - Bruteforced, jed file available at wiki.pldarchive.co.uk.
U17 PAL16L8 04-01
U19 PAL20X10 06-01
U21 PAL20X10 05-01
U22 20X8 Programmed to behave like a 74LS461 which can be used instead.
U23 20X8 Programmed to behave like a 74LS461 which can be used instead.
U26 PAL16R8 10-01
U27 PAL16R8 11-01
U40 PAL16R8 09-01
U42 PAL16R4 08-01
U43 PAL16R8 07-01
U45 20X8 Programmed to behave like a 74LS461 which can be used instead.
U56 20X8 Programmed to behave like a 74LS461 which can be used instead.
U60 20X8 Programmed to behave like a 74LS461 which can be used instead.
U85 PAL16L8 02-22
U96 PAL16L8 01-01 - Bruteforced, jed file available at wiki.pldarchive.co.uk.
I bruteforced, created jed files and tested the four PALs I could, this still leaves a lot that cannot currently be replaced but it's a start.
On to the repair.
The board would boot from cold and display the title screen but it was cut up into pieces and then would crash. Trying to boot the board again or pressing the reset button would result in vertical lines and the slave cpu resetting.
When replacing sockets I tested every chip I removed and found two bad 6116 rams and two bad 41464 rams which I replaced. I also found that R1 resistor next to the CPU socket U1 on the bottom board was only soldered on one end and the other end was just touching the pad, it must have been like this since it left the factory, so I soldered that on properly.
It still behaved the same though, next I found a bad 74LS374 @ U18 on the bottom pcb, replacing this fixed both the graphics and crashing issue.
I'll also replace the original battery from 1989 with a new CR2032 coin battery and holder.
The sound and digital controls all work but I haven't been able to test the steering as I don't have the 'opto coupler' board but hopefully this repair is complete.
Hello there - would you be able to help me with my Ivan Stewart's Off Road board?
ReplyDeleteThanks
meestermole at yahoo.com