TECH HELP: Gravitar

[vernimark]

[ukvac] TECH HELP: Gravitar
I bought a not working Gravitar PCB on Ebay. I cleaned it, resocket
all EPROMS (Black Widow) and custom chips, changed clock, changed
6502, and so on...
Now it works for 30-40 seconds (without sound) and then it doesn't
work any more. I turn off, wait 30 seconds, and when I turn on it
works again for 30-40 seconds and then it stops, and so on...
Sometimes one second before it stops all vectors move on the right
monitor side (I see only a vertical coloured line on the right).

Marco
(vernimark)



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[LukeWells]

Re: [ukvac] TECH HELP: Gravitar
Have you checked for activity on the board once it gets into its 'not
working' state. i.e. is everything still getting clock, is there activity on
the data lines? or has everything just frozen?

also check that the reset line is not creeping in and causing the problem.
I've had this before on a board where the reset voltage slowly dropped from
5volt to about 3volt after about 60seconds causing one of the cpu's to reset
and the other carry on running, but loose sync and everything go tits up

Luke

 

[vernimark]

[ukvac] Re: TECH HELP: Gravitar
I'll check this night


Thanks,
Marco