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2 eMac´s dead after connecting each other

Discussion in 'Macintosh Computers' started by lordvampire, Oct 25, 2005.

  1. macrumors newbie


    my problem: I have got an eMac 1.0GHz, which doesn´t boot after connecting
    two eMac´s via FireWire! The cable was bad!

    Now, i can not boot, no sound at the start, no light, nothing....
    Is it possible, that a bad FireWire cable, destroy my Logic Board??
    I opened it and tried to test my Logic Board... "test :)" i searched after voltage
    on the Board, and i found 12V ans 3,2V next to the NVRAM-Reset-Button!

    Does anybody know this problem?? How can i test my LogicBoard???
    Somewhere on the net i read, that the firewire-adapter can be destroyed, but not the whole board???

    best regards
  2. macrumors G5


    The Firewire circuit is on the motherboard AFAIK. Whether additional circuits are damaged, I don't know. Does it boot from the OS X CD?

    This will be a problem for you. I hope you have Applecare coverage. If you do, take it to an independent Apple service centre, you will have more of a chance of getting it repaired under warranty than going directly to Apple.

    What happens, either with a faulty cable, or even by inserting the Firewire cable slightly twisted, is that the power lines of the Firewire connection get shorted (even just a momentary spark) to the data lines, and the current flowing down the data connection fries the Firewire chip on the logic board. This is irreversible. I just had a customer blow a Mini-DV camera and an EMac logic board doing the same thing. The eMac was $700 repair but Applecare covered it. The camera is a writeoff -- $600 logic board plus $200 labour to fix it.

    The solution -- although Firewire is supposed to be hot-pluggable, make it a policy NEVER to plug or unplug a firewire cable on your machine while the machine or the peripheral is running. Power down first.

    Obviously, this does not protect you against a cable that is damaged and shorted internally. There might be a protection to be had from using a firewire hub on the machine, and making all of your connections through the hub.

    Powered busses (Firewire and USB both) that mix data and live voltage are a bad idea, IMO. Mistakes are very costly.

  3. macrumors newbie

    no it does not boot from the cd...
    when i press the power button, nothing happens, nothing! no fan-sound, no start-sound, no light.... i tried to reset NVRAM, it didn´t help!!

  4. macrumors 65816


    Sounds like you might need to reset the PMU. Page 47 of this PDF shows where the PMU button is. Hope it helps!
  5. macrumors 68020

    So every time you disconnect/connect FireWire... power down the whole machine and peripheral? Does that apply to USB too?
  6. macrumors 68020


    I plug/unplug my iBook into/from my eMac over firewire what must be every couple days without powering down either. No problems on either front.
  7. macrumors 65816


    By the way, something important I just remembered (doesn't seem to be in the eMac documentation, but it was definitely in the docs for my G4 PowerMac). Only push the PMU button once. If you do it more than once, it'll take a few hours to reset itself, which can be annoying and possibly misleading! :eek: ;)
  8. macrumors G5


  9. macrumors 68020


    Should that really be a problem? I thought computers have been hot-pluggable for a while now.

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