TECH: Data East Jurassic Park DMD dead

[powesmith]

Could really use some help on this. Been having issue with the DMD for a while, one day turned the machine on and DMD was totally dead. The power supply board was rebuilt, all voltages are were they suppose to be. I was able to get it working a couple of times by unplugging 5VDC and other connectors. The interesting thing is, once I get it to work, It will be working for as long as I turn the machine on once a day. If I let it sit for a week without turning it on, it goes dead. Last time I was able to see it coming to life for a split second and then it went dead again. I didn't replace the ribbon cable, but I did flip it on both ends, no effect. Any help would be greatly appreciated. My next step is to get the replacement, but I don't want to just through $$ away. Thank you.

[John Robertson]

On 2021/06/29 5:16 a.m., powesmith wrote:
> Could really use some help on this. Been having issue with the DMD for a while, one day turned the machine on and DMD was totally dead. The power supply board was rebuilt, all voltages are were they suppose to be. I was able to get it working a couple of times by unplugging 5VDC and other connectors. The interesting thing is, once I get it to work, It will be working for as long as I turn the machine on once a day. If I let it sit for a week without turning it on, it goes dead. Last time I was able to see it coming to life for a split second and then it went dead again. I didn't replace the ribbon cable, but I did flip it on both ends, no effect. Any help would be greatly appreciated. My next step is to get the replacement, but I don't want to just through $$ away. Thank you.
>

Based on your description I'd be checking the /Reset (Reset Low) signal
to the CPU on the Display Controller Board at this point.

That signal should be Low for about 500msec after the power is turned
on, then goes High - which is close to Vcc or 5.00VDC.

If the above means nothing to you see if one of your firends knows
enough about electronics to read a schematic and be able to test the
board...

John :-#)#

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[powesmith]

Thank you for the reply, will try to locate based on the schematics, will report back.

[powesmith]

ok, so based on the schematic, CN3-20 is reset which reads at 70mV, CN3-20 is STB which reads at 5VDC