Space duel signature analysis questions

Hello all,

After being away from the hobby for a while, I am trying to repair a
Space Duel. I am trying to use signature analysis to pinpoint the
problem using an HP5004 and a KK Signature II. I have wired the
processor for a NOP (0xEA) and am getting correct signatures for the
6502 as listed in the KK manual. Unfortunately these signatures differ
from those listed in the Space Duel schematics. The KK manual lists
additional signatures for the 6502a which match those in the
schematics. The question is: Why are these different? I'm certain that
this must have been discussed before, but a search of the vectorlist
archives offers nothing, neither do various google searches. Anyone
have any ideas?

Regarding the Space Duel itself, here are the symptoms.
1. The game does nothing in play mode. The watchdog is pulsing the
reset line. A little investigation shows that the processor is in a
loop waiting for the vector generator to change the halt flag, which
never occurs, hence the reset.
2. In selftest, the display is garbled at first. As the machine warms
up the display gets better. Note this is not a monitor problem, but a
game board problem. The switch settings are all shown correctly
although with K's rather than O's (or 0's). When a switch is pressed the
display correctly shows a 1 and sounds a tone. Other screens show
similar defects, vectors missing etc. I have tested the '244s and '245s
and all appear functional. All roms show correct checksums.

TIA for any and all help.

Best Regards,
John Ardern

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Received on Sat Apr 12 10:18:00 2003