Help with Dig Dug PCB....

oni2382

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Got a working Dig Dug pcb to restore a cab, and when I power it on the screen comes up and the board goes through its test, and then reads RAM OK...then immediately resets. Checking the chips and harness haven't helped. Any other suggestions?
 
Got a working Dig Dug pcb to restore a cab, and when I power it on the screen comes up and the board goes through its test, and then reads RAM OK...then immediately resets. Checking the chips and harness haven't helped. Any other suggestions?

I had one that had wrong/bad z80 chips in it. The z80 chips in that game should be z80a chips.

Also, you want to check the voltages on the chips. Mine was at about 5.15 then when I powered up the voltage dropped to about 4.84.

Feel for hot chips also, check the tmm2016 in the upper right corner and the ram chips also.

For some strange reason, the 07xx chips are very frail and fail quite often. Check them with a logic probe most of the pins should have signal on them.
 
ok will do.....Also if I need to adjust the voltage where can I do that on the power supply? There aren't any obvious knobs to adjust like on some other cabs....
 
WOW thats extremely helpful..As soon as I get a chance I'll check the voltages and give you all an update. Thanks again.
 
I had one that had wrong/bad z80 chips in it. The z80 chips in that game should be z80a chips.

Also, you want to check the voltages on the chips. Mine was at about 5.15 then when I powered up the voltage dropped to about 4.84.

Feel for hot chips also, check the tmm2016 in the upper right corner and the ram chips also.

For some strange reason, the 07xx chips are very frail and fail quite often. Check them with a logic probe most of the pins should have signal on them.

Have you checked the cpus? What kind or type are they z80 or z80a?

Have you checked the cpu lines to see what pins 21 through 26 are doing?

At this point a logic probe, a scope, and a multimeter are your best friends.

I have one of these (older) boards if you need readings let me know.
 
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