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saturizer

6502
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    22
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About saturizer

  • Birthday 05/16/1981

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  • Website URL
    http://thelocalgenius.com/

Profile Information

  • Gender
    Male
  • Location
    Moscow, Russia
  1. saturizer

    Macintosh Classic chessboard screen

    I'm in Russia, there are no specialists who repair obsolete Apple computers here, even finding a RAM for old iMac is a problem. If in US/EU there are at least hundreds of people collecting old computers, then in Russia there might be dozens or less. Shipping to US and back is too expansive (I could simply buy a working Classic instead), I don't know why, but recently shipping prices became weird. I know basic things about electricity, don't worry about me or my Classic, I'm pretty good with soldering, I always check the polarity and other stuff. The problem is that nobody knows this stuff for sure, beyond the leaking caps it is always a guess. If the name of the component were erased nobody can tell what it was. And as I said before, the number of the components on the board is finite and only a fraction of it could cause this particular problem, so I hope to solve the problem sooner or later (:
  2. saturizer

    Macintosh Classic chessboard screen

    Well, there is a problem — I'm in Russia, not sure that I would be able to find someone who repairs obsolete Apple computers. And shipping to US and back is too expansive. I think that this particular problem could be caused only by certain components' failure, unfortunately nobody knows these computers well enough to detect what's going wrong. So far I simply searched the web for the similar problem and replaced the mentioned components. I replace a component only if it was mentioned as a reason for a chessboard display problem and I'm sure it would work sooner or later.
  3. saturizer

    Macintosh Classic chessboard screen

    I have little experience in repairing such a complex electrical devices, can you give me a few hints? I've also replaced QP2 / IRFBC40 (mosfet), but still the same thing. I guess I'll replace every component on the analog board eventually... The voltage is still low.
  4. saturizer

    Macintosh Classic chessboard screen

    Replaced the big 400V, 220Mf capacitor as well. Still no changes.
  5. saturizer

    Macintosh Classic chessboard screen

    So, guys, I've finally got those chips (had to buy 35 of them and wait for several weeks), changed it, but everything is the same — perfect black and white rectangles. What's next?
  6. I just bought a Studio Display (M4551), with no power adapter and unfortunately this kind of adapters could not be found in my area. I've seen few items on eBay, but they were too expansive and including shipping to my destination it would have been more than 3 times more than the cost of the display itself. So I was thinking of finding some alternative or using iBook power adapter which has the same output, but I can't find information on the polarity (positive/negative) of the display's power cord. Polarity isn't mentioned on the original power adapter. Does anybody have this kind of adapter to check the polarity? Thanks in advance!
  7. saturizer

    Macintosh Classic chessboard screen

    Okay, but can I somehow test this component, to know for sure it has to be replaced? I wish to know it for sure, cause I have to order this chip with delivery within up to 3 weeks, so if the reason is not the opto-isolator, I'd waste pretty much time waiting for the replacement parts...
  8. saturizer

    Macintosh Classic chessboard screen

    http://ru.mouser.com/ProductDetail/Vishay-Semiconductors/CNY17G-3/?qs=%2fjqivxn91cdU561RMf2UFw%3d%3d This one?
  9. saturizer

    Macintosh Classic chessboard screen

    Okay, but I still don't have any idea of how it looks like. Is it possible to replace it or is it this machine specific?
  10. saturizer

    Macintosh Classic chessboard screen

    How does it look like or is it somehow signed on the analog board? Is there a way to test it to know it's corrupted for sure?
  11. saturizer

    Macintosh Classic chessboard screen

    Just checked the voltage from the analog board. +12V and -12V — 22,5V +12V and ground — 11V +5V and ground — 4V So, what components on the analog board could cause lower voltage? I can replace all the capacitors left, but it would be much better to know the reason. I would like to know what this VR1 thing is, cause if it's somehow related to video, than probably it's the reason of my problem, although that guy with the same problem got all those microchips in perfect condition with no corrosion at all...
  12. saturizer

    Macintosh Classic chessboard screen

    Yep, it looks like the problem is in the logic board, but in that Mac Classic story the logic board and those microchips near the capacitors were undamaged with no significant corrosion. That story seems important to me cause it's the only case where the pattern on the screen is exactly the same as the one I have. In all the other cases I saw, when there were leaking or dead caps, the patterns were more chaotic, while I have perfect b/w rectangles. I'm not quite sure I got you right about the microchips you've mentioned, could you please name them by their signs on the board (like VR1, UE8 and so on)? I was trying to find some kind of a scheme of the logic board with microchips' names and specifications, but haven't find anything so far.
  13. saturizer

    Macintosh Classic chessboard screen

    Thanks, I'll check this tonight! But what might cause lower voltage? Yes, it seems strange for me that he didn't tested both analog boards and compared the result...
  14. saturizer

    Macintosh Classic chessboard screen

    For the caps I've replaced I'm 100% sure everything is okay cause I checked every capacitor, its placement and +/- position before replacing it and after. The analog board is in very good condition, with no leaking caps, as I removed the dust, it looks like new. Maybe some other capacitors are broken on the analog board? Or other components? Where can I check voltage on the analog board safely (without a risk of damaging the board or multimeter)? I also found a story pretty like mine, but with no solution: http://appletothecore.me/files/leaky_caps.php
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