Image Map Image Map
Results 1 to 10 of 10

Thread: Atari 1200xl Black Screen

  1. #1

    Default Atari 1200xl Black Screen

    We have an Atari 1200xl computer which is in perfect physical condition. History of this machine is not known. When powered on, the power LED lights, the screen flashes red for a brief moment, then goes to pure black. There are two soft "pop" sounds from the tv speaker during the start up process as well. Pressing the reset button causes the two pops to be heard, but the screen remains black. We have tried both the RF and composite outputs with the same result. We have also tried 2 different power supplies, and swapped the ANTIC chip but the problem persists. I have removed and reseated all socketed chips, and moved the RAM chips around but there is still no change. Any assistance is appreciated. Thanks!

  2. #2
    Join Date
    Nov 2003
    Location
    Landenberg, PA USA
    Posts
    3,680
    Blog Entries
    1

    Default

    have you confirmed your TV works with another RF-video computer, like an atari 2600 or something? You should verify that you have a working video too.

    Do you have a cart installed in the cart port?

    Bill
    @ BillDeg:
    Web: vintagecomputer.net
    Twitter: @billdeg
    Youtube: @billdeg
    Unauthorized Bio

  3. #3

    Default

    Yes, the tv works with multiple other vintage systems using both RF and composite in. The only cart I have is the BASIC cart, and I have tried it both with and without the cart installed with the exact same result.

  4. #4
    Join Date
    Nov 2003
    Location
    Landenberg, PA USA
    Posts
    3,680
    Blog Entries
    1

    Default

    So, I fired up a 1200XL to see what happens using the composite jack with neither drives nor cart. You should expect the system to post an ATARI logo on the screen. I guess you have to troubleshoot the motherboard of the computer.


    (my son playing Pitfall!)
    @ BillDeg:
    Web: vintagecomputer.net
    Twitter: @billdeg
    Youtube: @billdeg
    Unauthorized Bio

  5. #5
    Join Date
    Sep 2012
    Location
    Indiana, USA
    Posts
    346

    Default

    Just swapping around the RAM chips might not be enough. It's very conceivable that more than one RAM chip is bad. Bad RAM will produce symptoms like yours on an 800XL, so I assume the same would be true for the 1200XL. Sometimes bad RAM will be warm to the touch, but not always. I would have had a very hard time repairing my XLs or my C64s without a way to test 4164 RAM chips.

  6. #6
    Join Date
    Nov 2003
    Location
    Landenberg, PA USA
    Posts
    3,680
    Blog Entries
    1

    Default

    I have a 64K and 256K RAM tester FYI. They exist.
    @ BillDeg:
    Web: vintagecomputer.net
    Twitter: @billdeg
    Youtube: @billdeg
    Unauthorized Bio

  7. #7
    Join Date
    Oct 2009
    Location
    Huntsville, AL
    Posts
    1,158

    Default

    Quote Originally Posted by billdeg View Post
    So, I fired up a 1200XL to see what happens using the composite jack with neither drives nor cart. You should expect the system to post an ATARI logo on the screen. I guess you have to troubleshoot the motherboard of the computer.


    (my son playing Pitfall!)
    That is a cool looking monitor.

  8. #8
    Join Date
    Nov 2003
    Location
    Landenberg, PA USA
    Posts
    3,680
    Blog Entries
    1

    Default

    It's the GE TV monitor / printer interface display. You can have multiple computers attached at a time, switch (box) on the front, plus a printer. Both RF and composite, with variations of audio. The perfect bench display.
    b
    @ BillDeg:
    Web: vintagecomputer.net
    Twitter: @billdeg
    Youtube: @billdeg
    Unauthorized Bio

  9. #9

    Default

    Thanks for the tips, I have swapped all RAM with known good chips and the symptoms are still exactly the same.

  10. #10

    Default

    Just wanted to close the loop on this thread, in case that it is helpful to anyone else out there. This issue was resolved by replacing the POKEY chip. I had noticed that the MMU chip was also getting a bit hot when the machine would not start, so we started by swapping that. However, the same symptom of black screen was present. Once POKEY was replaced, everything is now working perfectly.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •