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Shymon184

6502
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About Shymon184

  • Birthday August 31

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  • Gender
    Male
  • Location
    Slovakia
  • Interests
    Vintage Computers, Books, Films & TV, Digital Illustration

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  1. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    I am afraid that this isn't much use to my problem, because in the Mac 128K topic, the analog board was used on a wrong voltage, which doesn't apply to my case because I have international board; mine was made to be used on 240V. The Mac Plus topic concerns a burned transistor, which also might not apply to my case because I checked my transistors after reading the topic and they are not burned at all. I guess I shouldn't be so certain about irrelevancy of these two topics, but it just doesn't seem to me like they are applicable to my problem. My theory is that a component of the power supply is half-dead due to heat or age, therefore causes the voltage fluctuation when cold (since the checkerboard disappears when the voltage gets stable), yet the component isn't functional enough to produce sound. Based on this, I think the component or components are a part of power supply circuit and audio circuit. My theory might be wrong though, for I don't fully know how the Macintosh operates.
  2. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    Ah, if you could find them, I think it would be a useful help for my problem.
  3. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    Well, there’s no bulge in the bottom left corner in that picture, but techknight said it’s fine, so I guess that’s the end of my concerns. I still don’t like the shape though.
  4. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    That might be true, but let's be realistic, the material seems like plastic and if you look at the analogue board pictures above, you can see the other corners look alike, but the bottom left corner is out of shape, this leads me to believe that it was made to handle certain amount of heat and on that one corner, the amount of heat exceeded the operating temperature and it just melted. So something happened that should not happen normally.
  5. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    I am afraid that the T3 transformer is actually melting, here are the pics: I don't need circuitry knowledge to see that it really shouldn't be in this shape, also the bottom terminals in the first picture seem awfully fried/burned.
  6. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    No offence taken but this is why I did it: This is written in Classic Mac Repair Notes 2.
  7. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    Sure, here are some pics: It's an International analogue board btw. Ignore the C1, it's an equivalent replacement and it also handles the heat a bit better. P.S. if you want any specific pics, don't hesitate to ask.
  8. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    > I forget which threads they were, its been years. Oh well, that's unfortunate, but at least I know what's wrong with my Mac. This narrows down the list of possible problems a lot, so thank you very much. I'm reading The Dead Mac Scrolls at the moment and a lot of symptoms (especially the audio ones) point to the flyback transformer. I'm gonna do more research now.
  9. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    So, you're telling me that fluctuating voltage isn't normal? Well that's a start, now let's find the problem! What could go wrong with the power supply? I'm no expert in electrical circuits, but my tip is on the T3 transformer, last time I checked, it looked kinda fried up.
  10. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    I checked the voltage and I got these results: Upon startup the voltage (both 12V and 5V) started fluctuating, the 12V ranged from 9.n/aV to 12.08V and the 5V never went below 4V and for a second was 5V. Once the Mac got to the insert diskette screen, the 12V stayed on 12.08V and the 5V stayed on 4.98V (which is strange because I adjusted it to 5V a few months ago).
  11. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    Like I said, I adjusted it, but I can check again...
  12. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    That is more likely I think, but I can't quite figure out what went wrong, I adjusted the voltage to 5V and nothing has changed. Maybe the high voltage power supply is failing (I read something along those lines in Macintosh Repair and Upgrade Secrets or Classic Mac Repair Notes, can't remember which).
  13. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    Resolder the logic board? That's a no no for me, I can barely resolder the analogue board, I guess I'll have to find someone who's gonna do the job... Also other weird thing that happens with the picture is that over time, the picture just becomes wider, you can't see it expanding, you will only notice it when you use the Mac for a few minutes. Any pointers for that?
  14. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    I forgot to mention that the checkerboard screen disappears after few seconds and normal boot sequence occurs. Other important thing is that if I select "Restart" in the Special menu, there's no checkerboard when the Mac restarts. This leads me to believe that this issue is not related to RAM per se.
  15. Shymon184

    [HELP] Macintosh Plus Checkerboard screen

    Yup, I checked the pins before installing the 1Mb sticks, they seemed fine to me, all lined up perfectly.
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