Friday, 5 June 2020

Super Off Road (Ivan Ironman Stewart's) repair and notes

A Super Off Road board came in for repair, the first thing I had to do was make up a basic power and video harness to test it. It was completely dead, a look over the board revealed it was two non working pcbs (different serials) from different sets connected together with a big X in marker on each.

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 will be on jammarcade.net soon.
U54          PAL16L8      41-02 - Bruteforced, jed file will be on jammarcade.net soon.
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 will be on jammarcade.net soon.
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 will be on jammarcade.net soon.

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.

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