Image Map Image Map
Page 1 of 3 123 LastLast
Results 1 to 10 of 24

Thread: Model I Issues

  1. #1

    Default Model I Issues

    Greetings.

    After a move across country, two of my five Model I keyboards gave up the ghost. This first one, when turned on, comes up with a blank screen for about 5 seconds, then displays the first image. After a bit it displays the second image. Pretty weird. Your thoughts would be appreciated.

    Oh, although very similar, don't confuse this post with: http://www.vcfed.org/forum/showthrea...air-assistance
    Attached Images Attached Images
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

  2. #2
    Join Date
    Aug 2013
    Location
    Philadelphia,PA area
    Posts
    148

    Default

    Quote Originally Posted by Fooser View Post

    Oh, although very similar, don't confuse this post with: http://www.vcfed.org/forum/showthrea...air-assistance
    The first pic looks like you have no HSYNC/VSYNC just like #6 in the other thread points to. The second pic looks like the normal garbage screen that happens when you boot with an EI and no floppy in Drive 0.

    Tom

  3. #3

    Default

    I tried tweaking the variable resistors an got this image.
    Attached Images Attached Images
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

  4. #4

    Default

    Just for grins, I replaced IC's Z5, Z6, Z57 and transistor Q2 with spares I had laying around. Absolutely no difference.
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

  5. #5
    Join Date
    Mar 2013
    Location
    Chaffee, MO
    Posts
    1,606

    Default

    How about a close up photo of the monitor so we can see the characters across the rows and columns.

    To check the address lines, remove the DIP Shunt at position Z3 and power-up the system. If the screen fills with a pattern of
    “@9@9@9@9...”, then all the address lines A0 – A9 are good. The remaining address lines A10 – A15 can be checked for
    activity with a scope.


    Larry

  6. #6

    Default

    Quote Originally Posted by ldkraemer View Post
    How about a close up photo of the monitor so we can see the characters across the rows and columns.

    To check the address lines, remove the DIP Shunt at position Z3 and power-up the system. If the screen fills with a pattern of
    @9@9@9@9..., then all the address lines A0 A9 are good. The remaining address lines A10 A15 can be checked for
    activity with a scope.

    Larry
    Larry to the rescue... thanks again!

    Here is a picture with the DIP removed. When turning it on, it will either come up with a blank screen, or the picture attached. It's a crap shoot.
    Attached Images Attached Images
    • File Type: jpg 2.jpg (232.6 KB, 36 views)
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

  7. #7
    Join Date
    Mar 2013
    Location
    Chaffee, MO
    Posts
    1,606

    Default

    Don, If I zoom and squint at the Imagine I can see a partial filled in character and I can make out the @9.
    But, they are fuzzy and not the full characters of the character set. I'm thinking it is in the Character Generator
    or in the Row addressing for the Bit matrix that make up the character. Can you read the Character Generator,
    or do you have one to swap as a test?

    Larry

  8. #8
    Join Date
    Mar 2013
    Location
    Chaffee, MO
    Posts
    1,606

    Default

    We should be seeing the following:


    Larry
    @.png 9.png

  9. #9

    Default

    Quote Originally Posted by ldkraemer View Post
    Don, If I zoom and squint at the Imagine I can see a partial filled in character and I can make out the @9.
    But, they are fuzzy and not the full characters of the character set. I'm thinking it is in the Character Generator
    or in the Row addressing for the Bit matrix that make up the character. Can you read the Character Generator,
    or do you have one to swap as a test?

    Larry
    I replaced the 8046673 with a 8046670 and had the same results.
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

  10. #10

    Default

    Well we're back from being evacuated from the Almeda fire here in Oregon. We're very fortunate, the fire devastated the area... as close as the other side of the street, but our home is intact.

    Now I have time to play with my toys again! I think I've addressed all of the suggestions in this post and am out of ideas. Any further thoughts on the problem would be greatly appreciated.
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

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
  •