Image Map Image Map
Page 3 of 10 FirstFirst 1234567 ... LastLast
Results 21 to 30 of 92

Thread: PET 3032 garbage screen problem

  1. #21

    Default

    Quote Originally Posted by MikeS View Post
    Not sure what you mean; the relevant pins of the socket are bent out and up and connected appropriately (with a piece of paper underneath to prevent the bent out pins from touching the system socket), and the 6502 is just normally inserted into the socket.

    But sure, if you have two sockets that works as well and no piece of paper needed.

    If I could find mine I'd post a picture
    It wasn't clear which pins you were bending. Maybe if I'd looked at the picture better I'd have understood. Still making the power connections would be easier with a second socket.
    Dwight

  2. #22

    Default

    Quote Originally Posted by Dwight Elvey View Post
    It wasn't clear which pins you were bending. Maybe if I'd looked at the picture better I'd have understood. Still making the power connections would be easier with a second socket.
    Dwight
    20190826_213826.jpg20190826_214001.jpg20190826_213714.jpg

  3. #23

    Default

    Quote Originally Posted by dave_m View Post
    ... With a scope you can follow the square waves on the address lines. A0 will have the highest frequency of about 500 KHZ, A1 half of that, and A2 half of A1. If you spot something not in that pattern, you have found the problem.
    These are the values with the scope

    AB data.jpg

  4. #24
    Join Date
    Feb 2009
    Location
    Southern California, USA
    Posts
    2,646

    Default

    Guys,
    On looking at the videos of the PET screen, there is a lot of hash. Could there be a fault on the Screen Address bus? Bad multiplexer at F6, F5 or F3 (LS157) or noise on CLK1 which selects between display refresh and CPU address?
    -Dave

  5. #25
    Join Date
    Feb 2009
    Location
    Southern California, USA
    Posts
    2,646

    Default

    Quote Originally Posted by Fran View Post
    These are the values with the scope
    Looks OK. Good work!

  6. #26

    Default

    Hi

    Today I replaced the 6502 and the pet works, the prompt appears, but with garbage, the keyboard works as you can see in the video.



    the original 6502 is faulty

  7. #27

    Default

    Either the addressing from the CPU side or the addressing from the video side is not working correctly.
    Dwight

  8. #28

    Default

    Quote Originally Posted by Fran View Post
    Hi
    Today I replaced the 6502 and the pet works, the prompt appears, but with garbage, the keyboard works as you can see in the video.
    the original 6502 is faulty
    sorry, this is not correct, I have plugged and unplugged the original 6502 several times and it works, with garbage and keyboard.

  9. #29
    Join Date
    Feb 2009
    Location
    Southern California, USA
    Posts
    2,646

    Default

    Fran,
    Did you check the signals from the chips mentioned in message #24 using the NOP Generator?

  10. #30

    Default

    Yes dave_m
    Input values F3-F5-F6:
    UF3_UF5_UF6.jpg

    What other signals/values must be checked on F3-F5 and F6?

    I have doubts if the C3 waves are correct, the output waveforms must be the same as the input waveforms? The output waveforms in B3 are very similar to the input waveforms

    AB0 OUT 6502
    Pin9_AB0.jpg

    C3 input wabe it is the same

    C3 out
    UC3_OUT_AB0.jpg

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
  •