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Thread: Mac Color Classic Won't Turn On

  1. #1
    Join Date
    Jun 2018
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    Los Angeles, CA
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    Default Mac Color Classic Won't Turn On

    I recently bought a Mac Color Classic but after plugging it in, it won't turn on. I tried flipping the power switch and then pressing the power button on the keyboard but nothing happens. However, when I take out the logic board and flip the power switch, the computer fan starts up and the hard drive moves. I'm assuming the logic board has some shorted capacitors. Before I buy replacement capacitors and de-solder all the old ones, is there anything else I should try?

  2. #2

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    Start with replacing all the caps on the logic board. Make sure you thoroughly clean off any electrolyte residue before installing the new capacitors. As your replacing them look out for broken traces as per below - if you find some then repair them!

    In my experience that usually fixes them; however I have had other obscure faults with colour classic's not powering on.

    If it still fails to power on after replacing the capacitors check the continuity between the CUDA chip to all of the other things it's connected to. I had one logic board which had a bad VIA to the CUDA crystal and other logic board which had a broken trace due to the capacitor leakage. If you find a trace which is discontinuous then triple check you've measured it correctly (i.e. haven't measured the wrong point-to-point) and then bridge it out using some wire.

    Someone on 68kmla wrote up their experiences with repairing broken traces/VIA's on a CC which might be useful. You can find it here: https://68kmla.org/forums/index.php?...ssue-debunked/
    System 80 Expansion Interface located! Thanks to all who helped out and the good people in the NZ vintage computer forums!

  3. #3

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    3pcedev’s right - most likely the capacitors have all had it.

    The Color Classic was one of a number of Macs that woukd not power up if the PRAM backup battery’s terminal voltage was low. Try removing the battery and see if it power up then.

  4. #4

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    Another vote for caps. Almost all 68030 Macs by now have rotting capacitors. The good news is, once you replace them and clean it up, it has a very good chance of working.

    Alternatively, if you have a "Mystic" logic board, you can try slotting that in as a replacement: http://colourclassicfaq.com/mobo/mystic.shtml
    I use my C128 because I am an ornery, stubborn, retro grouch. -- Bob Masse
    Machine room: http://www.floodgap.com/etc/machines.html

  5. #5
    Join Date
    Jun 2018
    Location
    Los Angeles, CA
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    Default

    If I'm going to replace all the caps on the logic board, should I go ahead and replace the ones on the analog board too?

  6. #6

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    Couldn't hurt.
    I use my C128 because I am an ornery, stubborn, retro grouch. -- Bob Masse
    Machine room: http://www.floodgap.com/etc/machines.html

  7. #7

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    Quote Originally Posted by willmurray461 View Post
    If I'm going to replace all the caps on the logic board, should I go ahead and replace the ones on the analog board too?
    In my experience (with 3 CC's) I found that the analogue board caps were all in good condition. I actually recapped 2 of them; but after testing the old caps on an ESR tester it was a waste of time. All were in spec.

    If you are like me and want to do it anyway there are two ways of doing it. You can either recap the switchmode PSU part (which powers the logic board, as documented on maccaps) or recap the entire thing.

    If you recap the entire thing then plan on adjusting the video circuitry. Speaking from experience adjusting the video is a painful job; one CC took me and a friend about 2 hours to get the image correct. Each setting changes another.....
    System 80 Expansion Interface located! Thanks to all who helped out and the good people in the NZ vintage computer forums!

  8. #8

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    Sorry, this may have been tried but my color classics won't boot without the PRAM battery installed. I can make one of them boot if I press the CUDA button on the motherboard before pressing the power on key on the keyboard. Not all color classics have this CUDA button (it's a little red button by the battery) I can reach it with a pencil (or something non-conductive) with the logic board installed when the back cover is off.

  9. #9

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    My CCs won't boot without a PRAM battery so I would try that. I can also get them to boot by pushing the CUDA button with a non conductive object from the back of the unit and then pressing power on on the keyboard. Not all CCs have CUDA buttons though.

  10. #10
    Join Date
    Jun 2018
    Location
    Los Angeles, CA
    Posts
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    Default

    So, a quick update: I ordered replacement capacitors but they haven't arrived yet, but after leaving the machine plugged in for a bit, it was able to boot up and run. It said that my clock battery was dead, but it still booted and worked just fine. However, the next day, I tried to turn it on and got the chimes of death. I'm going to wait until I get the capacitors replaced and then see what happens.

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