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Atari 800 XL black screen


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Really, the only sure-fire way to troubleshoot these machines is to have 2 of them, or to have extensive diagnostic equipment. It's easier to swap components into a working machine and isolate the bad parts.

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I think your best bet is to watch ebay for a junky looking machine that goes cheap for parts. All 600XL's I've seen were socketed and they contain the same chips (except for the RAM). IIRC the XE's are never socketed. As long as the machine doesn't do anything, it's a crap shoot which chip is bad. I don't think I've ever seen a Pokey get even warm.


Completed 600XL that went for $20+shipping:




Nice idea, but getting another non working computer "for parts" may be as much difficult to diagnose than the only one I have. Unless I can find one locally.


For the same price, I better order the chips and test them one at a time...

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I finally got in touch with the guy my friend's got it from. He tested the PIA, GTIA, Sally and Antic chips, and they were all working fine.


He also tested Pokey, and confirmed this one is not working on my 800XL. He also tested his Pokey on my board, but this test proved that something else on the board is faulty because he got the black screen too. He stopped testing at that point.


This means it could be the MMU or RAM that is faulty in addition to the Pokey itself. He should validate if the MMU and Ram are socketed on his computer, and I'll try to investigate further with him if we can meet together.


Great so far. I've got further down the path of a resolution...

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Ok, now I know better what can be wrong with my 800XL:


- the guy tested the GTIA, PIA, ANTIC and Sally chips in his working 800XL, and they worked

- he tested Pokey, and it failed. Putting his good Pokey on my board failed, so another component is bad

- he tested the RAM and was fine

- he could not test the MMU or RON chips as they are soldered on his board


I contacted Best Electronics for pricing of components:


CO12294 Pokey U$D 20.00

CO61598 OS U$D 12.00

CO61618 MMU U$D 14.00

8 CO60612 Ram chips U$D 12.00


Or I can buy a working 800XL main board for $70.


Probably my best bet is to buy a working board with sockets and clearly identified the bad parts as the price will be similar in the end.


I'll also need to buy some joysticks, any recommendations on theses? And Atari and Commodore have compatible joysticks?

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  • 5 weeks later...
  • 2 months later...



I finally ordered a new 800XL board from Best Electronics, and received it today. I installed it in my 800XL and it starts normally.


With one exception: the keyboard is sending the "F" letter constantly, which prevents me from using it normally.


Any suggested path of investigation you can suggest?

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It is finally working.


The issue was weird...


I removed the F key and the white plastic to look at the springs. Nothing wrong there, but the F key was still repeating.


I tried cleaning it with compressed air and alcool, nothing worked...


So I remove the ~10 screws that maintain the keyboard to the metal plate, and connected the membrane only to the computer, and the F key was no longer repeating. By typing on the membrane itself, all keys were working as expected.


I then reinstalled the keyboard to the metal frame with the membrane, tested it, and it worked...


Basically, I thing it was some small thing stocked between the keyboard and the membrane doing a false contact. By just removing the keyboard from the membrane it freed the culprit item and now I have a 800XL like new. :)


I just need to ket software now and start using it.


Thank you all

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