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Apple A2M6021X Monitor Repair.

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  • #46
    Originally posted by nauseous View Post
    I just went through and re-capped one of these monitors overnight, thought I might put this here for future reference.

    Capacitor List:
    C390 - 50v, 47uf
    C211 - 50v, 1uf
    C135 - 50v, 1uf
    C130 - 50v, 10uf
    C102 - 16V, 100uf
    C111 - 16v, 10uf
    C203 - 50v, 0.47uf
    C213 - 50v, 0.47uf
    C309 - 35v, 470uf
    C218 - 50v, 0.47uf
    C138 - 25v, 1000uf
    C209 - 16v, 100uf
    C117 - 50v, 0.47uf
    C136 - 16v, 1000uf
    C120 - 50v, 0.47uf
    C220 - 16v, 47uf
    C305 - 35v, 470uf
    C302 - 25v, 1000uf
    C312 - 50v, 10uf
    C310 - 35v, 22uf
    C308 - 50v, 1uf
    C161 - 25v, 47uf
    C501 - 400v, 220uf
    C502 - 160v, 1uf
    C505 - 100v, 0.47uf
    C503 - 50v, 1uf
    C101 - 50v, 1uf
    C509 - 160v, 220uf
    C224 - 160v, 1uf
    C201 - 50v, 1uf
    C140 - 250v, 22uf
    C908 - 250v, 1uf (Neckboard)
    How did it come up?

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    • #47
      Very similar to before replacing capacitors (was hoping this would have resolved fault - but clearly something more going on). But that's OK as at least all of the above are now ruled out. You can't really see in the photo but the monitor is showing output. APPLE II and the console prompt is visible but scrolling.

      Just working on getting a complete list of symptoms at the moment. Some of the adjustment pots look to be dirty / stuck.

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      Would it make any difference driving this from a Apple IIe (currently testing with a Apple +) ?

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      • #48
        is switch 800 in the correct position? https://www.aussiearcade.com/forum/g...air#post101187

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        • #49
          Switch does appear to orientated correctly.

          Just spent a little bit more time and went over all the pots to get those stuck moving again. I can hear the monitor's EHT come on, but the screen just stays black. I guess it's time to double check the adjustment pots...

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          • #50
            Got a little further with this over the weekend. I am suspect that the TA7644BP is faulted. It looked dubious when I first opened the case.. The earth strap on the back of the monitor had disintegrated and made a mess of the chassis. Subsequently I cleaned the chassis and replaced earth strap (plus a few other components).

            The picture on screen comes and goes at random, when it is visible the adjustments make no difference to the display (brightness, contrast, v/h hold, size).

            Last night digging around on the internet I have found that the Samsung 20K20 chassis is almost identical to this model Apple. Same IC's, very similar internal wiring, even to the point it has a 3 way service switch. Mind you being a TV set it has extra circuitry for the tuner portion, but this is drawn separate to the actual CRT workings. I'm sure there will be subtle differences between this and the Apple monitor so use it purely as a guide to aid you in troubleshooting. I am doubtful that component labels/values match exactly.

            Here is a link to the schematic https://elektrotanya.com/samsung_20k.../download.html




            Click image for larger version

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            • #51
              Thank you all for all the info regarding that monitor . I got mine from a guy who had it stored under the house . The outside looks great , but the inside is all corroded where it can be . My first try was to plug it in , it lit up , then pop . Decided to open the case ( should have done that first ) , found C908 had popped , replaced it , tested it on , but nothing . Decided to pull it completely apart and give it a good clean . Like on the post above the earth strap has disintegrated and messed up the board . The exposed aluminium on all caps was badly corroded , so decided to replace them all ( in progress ) . The TA7644BP was wet and the pins badly damaged , corroded , rusty with green stuff on some . Decided to remove it and waiting for a replacement . Cleaned all the corrosion on anything , repaired the rust in the brackets etc. Next ,will test all the diodes , transistors and resistors , as well as I can , before reassembly and test .Checked the caps list , so far all match , except C101 , where mine is a 47uF 50V , near the video in socket . Still have a few of the smaller ones to do . Slow progress , slow delivery of parts .

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