Marble Madness - Repair Log - 6502 not responding

ArcadeDanger

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Donor 2013, 2015
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The other day I turned on my Atari System 1 cabinet that contains Marble Madness (this was after it had been brought back from MAGWest). I noticed that the sound wasn't working, but game was playing.

I was cleaning the garage and relocating things, including MM. When I powered up the row, it came up with the '6502 not responding'.

This boardset is pretty temperamental, many times it comes up scrambled, resetting over and over, and other times it bongs loudly and says 'software exception'. There's probably a broken trace somewhere and it only works if the main board is a few millimeters leaning over. However, usually re-seating the daughter board resolves this. That did not work this time.

It was able to go into test mode, but the sound test reported it was unable to communicate with the CPU. Note, that the signal for the test switch carried by all the wires at the top of the board that provide video signals and trackball inputs.

Pulled out the boards; popped off the 6502 on the main (top) board cleaned the legs with some alcohol and reseated it. No change.

Went to search on the internet for this error. One post mentioned this only happening on Marble Madness and that Road Blasters and Indiana Jones were ok. Several repair logs mentioned a pile of things: could be the actual 6502, bad ROM chips (B12 and D16), some control chips with tarnished legs (R6522-33 and the TMS5220NL chip on MM board), a service bulletin mentioning a pull-up resistor may be missing (2.2K resistor near/from IC location 13F pin 2 to +5V).

As it turns out, I have a Space Duel boardset on the shelf, that runs with a 6502A. Swapped that in, and success, Marble Madness is back in business.

I'll order up a new 6502 to backfill Space Duel.
 

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