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Thread: Pet 2001 9" Monitor, spot killer.

  1. #1
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    Default Pet 2001 9" Monitor, spot killer.

    Does anyone have a repair guide to fix the spot killer on a original 9" 2001 Chicklet pet?

    I remember it should be a cap, but my google skills have come up short today.

    Monitor works fine otherwise.

  2. #2
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    I don't think the original 9" screen had a "spot killer". It happens on every 9" PET monitor I've ever encountered and I've heard some say it was normal when they were new.

    I've been testing a spot killer MOD that was devised by IZ8DWF. Adrian Black has also tested it on a few different PETs and the results are inconsistent so far.
    It appears that differences in component aging or board design are still allowing cathode current to leak and the spot still appears though it can be reduced quite a lot.
    There was some recent discussion about this on the CBM Facebook group related to C22, but my attempt to try that fix didn't work at all.
    https://www.facebook.com/groups/2145...91816214361267

  3. #3
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    I agree

    My 3032 'spots' and I certainly can remember it on the chiclet PET at school.
    Current fleet
    TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225

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    I agree

    My 3032 'spots' and I certainly can remember it on the chiclet PET at school.
    Current fleet
    TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225

  5. #5
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    Well, I went ahead and disassembled the monitor to check it, and I never recapped it... Original caps dated, 7830... Ouch.

    It's a 320084 model, so a early 9" version.


    I'll live with the spot, but I'm going to order caps.

  6. #6
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    Quote Originally Posted by dabone View Post
    ... I'll live with the spot, but I'm going to order caps.
    Make sure you get low ESR caps where required. Some of them (I believe related to the deflection circuit) require low ESR and if not they will get hot.

    I'll be interested in the results. I've never re-capped one and when I was thinking about it, I was warned against doing it by someone in this group who know much more about it than I do.

  7. #7

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    Interestingly, I tried changing C22 on the video board from 3.3uF to 47uF on my 9inch monitor and that killed the spot... (it appears the early boards had 3.3uF and the later revision 47uF) though reading various posts it seems that doesn’t always work as you say.

    Quote Originally Posted by Hutch View Post
    I don't think the original 9" screen had a "spot killer". It happens on every 9" PET monitor I've ever encountered and I've heard some say it was normal when they were new.

    I've been testing a spot killer MOD that was devised by IZ8DWF. Adrian Black has also tested it on a few different PETs and the results are inconsistent so far.
    It appears that differences in component aging or board design are still allowing cathode current to leak and the spot still appears though it can be reduced quite a lot.
    There was some recent discussion about this on the CBM Facebook group related to C22, but my attempt to try that fix didn't work at all.
    https://www.facebook.com/groups/2145...91816214361267

  8. #8
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    Quote Originally Posted by AndyG View Post
    Interestingly, I tried changing C22 on the video board from 3.3uF to 47uF on my 9inch monitor and that killed the spot... (it appears the early boards had 3.3uF and the later revision 47uF) though reading various posts it seems that doesn’t always work as you say.
    Yes. I think that cap was changed by Commodore for the sake of the spot. I think it holds the brightness voltage low a bit longer after power off to suppress the spot. I tried it but it didn't fix the problem for me.
    My brightness voltage is not what it should be though. It's supposed to be -30v but I'm only getting around -20v and I can't turn the brightness down far enough for the display to even get dim.
    Last edited by Hutch; November 18th, 2020 at 01:55 PM.

  9. #9
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    Mine apparently is a different model that those.

    C22 is a non-electrolytic, and is labeled 001 on the layout sheet.


    The only place I found schematics/board layout is here.

    http://vintagecomputer.ca/files/Comm...une%201978.pdf

    The component cross reference list doesn't match the video board at all.
    (Just compare it to the layout on page 11)


    The board is labeled 320084, the underside of the board is blue, plain fiberglass on the component side.

    The following caps currently installed.

    C1,47uf,16V
    C4,3.3uf,200V
    C12,220uf,35V
    C14,1uf,25V
    C15,3.3uf,200V
    C21,470uf,16V
    C16,10uf,25V
    C23,47uf,16V
    C26,47uf,16V
    C25,4700uf,25V
    C27,47uf,16V

  10. #10
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    FYI, you can find schematics for the different revisions of the 9" monitor for the 2001 and 2001-N on Zimmers, here http://www.zimmers.net/anonftp/pub/c...pet/index.html
    The one I'm working with is the very first rev for the 2001-8 (link http://www.zimmers.net/anonftp/pub/c...deo-layout.gif)

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