• Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.

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  1. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    For closure: it was the flyback. I picked up another grungy Mac Plus with a working display. I did some parts swapping and tried every combo of analog board, CRT, and logic board. The problem followed the old analog board. Then I swapped flybacks between the analog boards and the problem...
  2. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    Thanks everyone! I think my next step is to buy a parts unit with a newer (and working) flyback. I wouldn't mind replacing my CRT as well since it has burn-in.
  3. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    I haven't done anything with the logic board. I attached an image of what I think is the video logic...? Appreciate the help.
  4. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    Here are a few things I just tried. The problem persists -- no better, no worse. 1) Replaced C1 again. My original replacement was a NOS electrolytic and I thought maybe it was bad too, so I put in a ECW-FD2W395K 3.9uf film capacitor. No change. 2) Replaced the horizontal output BU406 at Q3...
  5. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    Thank you for responding. The main rails are 5.04V and 12.1V and steady. If you are asking about voltages in the CRT drive circuitry, I am not sure what to measure.
  6. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    The problem starts as soon as I turn on the Mac. I did try it without the floppy attached and no change. I'll look into replacing that transistor. I attached a video of the problem here to better represent it. (note: the image doesn't sway back-and-forth -- that's me being unsteady holding...
  7. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    Update: Swapped out C1; no change.
  8. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    Clarification: My cap kit didn't include C1 so I didn't replace it. Mine is electrolytic. I've seen it described as the "horizontal deflection capacitor" and highly likely to fail, so that is very suspicious and I will find a replacement for it. Other ideas still very welcome!
  9. M

    CRT on Mac Plus -- rows randomly offset by 1-2 pixels

    Hi, first post, glad to be here. I have a new-to-me Mac Plus. It appears to be an earlier Mac that was upgraded. It has the Samsung CRT and the "early" flyback transformer without yellow(brown) glue on it. It has a 4MB RAM upgrade. The problem with the CRT is that some horizontal rows will...
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