Image Map Image Map
Page 1 of 4 1234 LastLast
Results 1 to 10 of 32

Thread: A2M2010 Apple II monitor all of a sudden started showing double image! Help

  1. #1
    Join Date
    Jan 2012
    Location
    Connecticut, USA
    Posts
    2,283

    Default A2M2010 Apple II monitor all of a sudden started showing double image! Help

    So my workbench monitor for the past 4 or 5 years has been my trusty little apple II a2m2010 monochrome composite monitor. Only problem it ever had was a dirty potentiometer for the contract knob I replaced. as of this week it started showing a double image. The top half of the screen is the image compressed with the top cut off, the bottom half is the same image but very compressed , almost like the scrolling star wars text. See image: aiimon.jpg

    doesnt matter which computer I connect to it or which cable I use. Just happened out of the blue. Any ideas what I should look for?

  2. #2

    Default

    adjust the vertical linearity control labelled VLIN but it's inside on the board, you'll have to remove the back cover. Turn it to expand the bottom, then you might need to tweak the height control on the back to the right size.
    Of course the controls might need cleaning too

    Larry G

  3. #3
    Join Date
    Jan 2012
    Location
    Connecticut, USA
    Posts
    2,283

    Default

    I have a spare CRT board in hand to reference. I see 3 internal pots, V.lin, Focus, and H.Hold. I am wondering are these just 500 ohm variable resistors? If so I have some I can replace them with. I have had some get pretty corroded where they just cant settle on a specific point.

  4. #4
    Join Date
    Apr 2015
    Location
    Austin, Texas
    Posts
    1,695

    Default

    Just make sure that you use the right pot. The ohms rating is half of it, but you need to determine if they're linear or logarithmic pots.

  5. #5

    Default

    manual with parts list is in here:

    ftp://ftp.apple.asimov.net/pub/apple...are/misc/sams/

  6. #6
    Join Date
    Jan 2012
    Location
    Connecticut, USA
    Posts
    2,283

    Default

    Thanks for much retrogear. If you can find me a similar manual if not a schematic for the apple A2m6020 your my new hero.

  7. #7

    Default

    Quote Originally Posted by VERAULT View Post
    So my workbench monitor for the past 4 or 5 years has been my trusty little apple II a2m2010 monochrome composite monitor. Only problem it ever had was a dirty potentiometer for the contract knob I replaced. as of this week it started showing a double image. The top half of the screen is the image compressed with the top cut off, the bottom half is the same image but very compressed , almost like the scrolling star wars text. See image: aiimon.jpg

    doesnt matter which computer I connect to it or which cable I use. Just happened out of the blue. Any ideas what I should look for?


    This is a fun fault. All that has happened is that the vertical scan rate has dropped in half (and it's still managed to stay in V lock on alternate V sync pulses and keep the correct height) so you are seeing the image presented twice on the vertical axis. Under these altered conditions one would expect the V linearity to be off, so that doesn't require adjusting most likely.
    It will be very easy to sort out with the scope. I have difficulty reading the schematic on the iPad I'm on, I get home later today and I'll look at the schematic on another computer and make a suggestion where to test.

  8. #8

    Default

    oh yes, Hugo is correct, I didn't catch that the image is duplicated twice. Does the vertical hold control have any effect? It could be as simple as that control went open and just needs cleaning
    or since the shaft sticks out that it got bumped and cracked the solder or trace on it

  9. #9

    Default

    Yes, the V hold pot wiper could simply have gone O/C try to exercise the pot & check its connections.

  10. #10

    Default

    The schematic mostly shows the V hold pot as a variable resistor,likely though it is wired in circuit with the wiper connected to one adjacent leg. This means of course if it turned out that when the situation was "normal" with normal vertical frequency, that the pot was near its mechanical centre , then if the pot wiper did go open circuit, the resistance of the pot would nearly exactly double, halving the scan frequency and giving a locked vertically doubled image that you are seeing.

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
  •