Fault 1: game randomly resetting and not booting reliably
This was quickly traced to an intermittent +5v from the supply by playing the game whilst a voltmeter was hooked directly to some fabricated test points on the PSU. (+12v was stable, input to the PSU from the 'suitcase' power brick was within spec.
I'd already replaced most of the semiconductors (eg power transistors) in a recent attempt to shotgun it so on trying to readjust the 5v pot and noticing it's movement felt like grit I thought I'd pull it and test. Instead of 100 ohms it read something in the region of 2K and the wiper wasn't any better. Examination showed acid damage which I suppose is pretty common on these. Replaced pot, problem solved.
Fault 2: oil slick light only comes on occasionally, when the game has been on for a long time.
Bulb tested good, traced continuity back to pin 7 of J1 on the lamp driver pcb (good) thus ruling out bad bulb holder, etc . Fault traced to bad output on IC U2 on the lamp driver pcb.
Fault 3: steering and 'gas' pedal incorrect values.
Mid game these went to full left and full throttle. This is roughly the same as disconnecting the absolute position pcb entirely. Checked power supply/gnd to AP pcb (good), checked power getting to 'gas' pot and changing values on the 'wiper' connection (easiest to reach from back to take readings). Reseated connections on AP pcb (no change) reseated J5 on SSI main logic pcb stack and the problem went away. I suspect bad contact on header/connector J5, or bad pcb trace nearby I suspect this needs further investigation before conclusive diagnosis and that the issue may return.
This was quickly traced to an intermittent +5v from the supply by playing the game whilst a voltmeter was hooked directly to some fabricated test points on the PSU. (+12v was stable, input to the PSU from the 'suitcase' power brick was within spec.
I'd already replaced most of the semiconductors (eg power transistors) in a recent attempt to shotgun it so on trying to readjust the 5v pot and noticing it's movement felt like grit I thought I'd pull it and test. Instead of 100 ohms it read something in the region of 2K and the wiper wasn't any better. Examination showed acid damage which I suppose is pretty common on these. Replaced pot, problem solved.
Fault 2: oil slick light only comes on occasionally, when the game has been on for a long time.
Bulb tested good, traced continuity back to pin 7 of J1 on the lamp driver pcb (good) thus ruling out bad bulb holder, etc . Fault traced to bad output on IC U2 on the lamp driver pcb.
Fault 3: steering and 'gas' pedal incorrect values.
Mid game these went to full left and full throttle. This is roughly the same as disconnecting the absolute position pcb entirely. Checked power supply/gnd to AP pcb (good), checked power getting to 'gas' pot and changing values on the 'wiper' connection (easiest to reach from back to take readings). Reseated connections on AP pcb (no change) reseated J5 on SSI main logic pcb stack and the problem went away. I suspect bad contact on header/connector J5, or bad pcb trace nearby I suspect this needs further investigation before conclusive diagnosis and that the issue may return.
