Gravitar - not running

modessitt

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Spot killer on. Not playing blind. Test switch does nothing (no beeps).

If it has a bad AVG chip, it should still run, right?

Already tried swapping in another ARII with no change. +5.08 at the ROMs. Swapped in a known-good 6502 and rotated a known good pokey through both spots (unless both are bad) without a change.

I guess the next step is to verify the ROMs? Don't have access to another Gravitar or Space Duel to check it in.

The monitor had been rebuilt a year or so ago, and I didn't see any issues, but it should still play blind even if the monitor had failed.

Any ideas?
 
Same problem here. Tested all roms and they are OK. Next step is to swap the AVG.

The machine was put in to storage working 10+ years ago.

New big blue cap, voltages are good.

P1 and P2 LEDS stay on.

JD
 
Generally the board won't run with a bad AVG (but its depending on the failure mode)

Mike
 
Also if the program ram is bad, it won't even load self test.

Bad AVG can cause it to not to run self test, or play blind.

I'd check the roms, and then start checking address and datalines as well.
 
I do not have another game to test this in. I took the AVG chip out and put it in a Star Wars PCB (Star Wars has dead monitor). My theory was that if the AVG chip was bad enough to keep the Gravitar board from running, it should keep the Star Wars board from running also. Nope. Star Wars plays blind with the Gravitar AVG chip.

So - I'm going to verify all the ROMs and then if they check out, look at swapping the Big Blue for giggles...
 
Tested all the ROMs. J1 (204) didn't test properly like the others so I burned a new one that did test properly.

Still doesn't work.

Next I'm swapping in another power brick just rule that part out...
 
Tested all the ROMs. J1 (204) didn't test properly like the others so I burned a new one that did test properly.

Still doesn't work.

Next I'm swapping in another power brick just rule that part out...

Good call, excessive AC in the +5 line can cause this behavior. You can also check the +5 line on the AC setting of your meter to get a pretty good idea.

My first step when troubleshooting a PCB is to remove every socketed chip, clean the legs, spray contact cleaner into the sockets, and reinstall. This usually gets it booting enough to play blind or have self-test tell you what else is wrong. If it isn't booting after all that, break out the logic probe and see if you have clock to the CPU.
 
Tried swapping in a Big Blue of unknown status with no change.

Swapped in a complete known-working power brick and it now works.

My boss is anxious to deliver so I probably won't get a chance to figure out the problem with it now...
 
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