joetechbob
Member
I recently picked up a non-working Defender which I'm having issues getting to boot. I suspect that this is due to a ROM failure, but I wanted to check with the Defender experts.
Here's what I've found:
1) When I got the game, +5 was missing and one of the fuses was blown. Replacing the fuse restored +5. I now measure good +5, +12 and -5 at the power supply.
2) With +5 restored the game started making the Defender boot noise and displaying the "rug" pattern, which gets redrawn regularly. Also, on power up, all four ROM board LEDs momentarily light solid and then turn off (no flashing). The same happens when the CPU board reset it depressed.
3) Voltages look pretty good at the RAM chips (-5, +5 and +12), though +5 is measuring at around +4.9--not sure how sensitive the RAM chips are to +5. Didn't detect significant AC rippled in the DC voltages.
I tried re-seating the ROM decoder chips, CPU and ROM chips (including cleaning the legs if necessary) and inspected the solder joints around the header connectors--joints looked good with a visual inspection.
Having looked online I believe this is a ROM failure. Does that sound about right? My next step is to try reflowing the solder on the header connectors (even though they look good), and potentially replace the ribbon cable between the CPU and ROM boards.
Does that sound about right? Any other advice?
Here's what I've found:
1) When I got the game, +5 was missing and one of the fuses was blown. Replacing the fuse restored +5. I now measure good +5, +12 and -5 at the power supply.
2) With +5 restored the game started making the Defender boot noise and displaying the "rug" pattern, which gets redrawn regularly. Also, on power up, all four ROM board LEDs momentarily light solid and then turn off (no flashing). The same happens when the CPU board reset it depressed.
3) Voltages look pretty good at the RAM chips (-5, +5 and +12), though +5 is measuring at around +4.9--not sure how sensitive the RAM chips are to +5. Didn't detect significant AC rippled in the DC voltages.
I tried re-seating the ROM decoder chips, CPU and ROM chips (including cleaning the legs if necessary) and inspected the solder joints around the header connectors--joints looked good with a visual inspection.
Having looked online I believe this is a ROM failure. Does that sound about right? My next step is to try reflowing the solder on the header connectors (even though they look good), and potentially replace the ribbon cable between the CPU and ROM boards.
Does that sound about right? Any other advice?
