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Imac 27 Repair

Discussion in 'Troubleshooting and Repair' started by Svoy, Jan 24, 2013.

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  1. Svoy

    Svoy

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    Jan 24, 2013
    Hi guys,
    Could you please help me to find out this one:
    http://i1212.photobucket.com/albums/cc456/Svoy/IMG_0208_zps97ddd7f0.jpg
    It is from Imac 27 (mid 2011) power supply, it blows the fuse every time when I plug in, so on closed inspection I found out that these capacitors have cracks...
    I would really appreciate for the help
    Thank you in advance.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I would check that you don't have shorted rectifier diodes (presumably there's one just near that capacitor) or more likely the main switching mosfet.

    The capacitor *may* be damaged, but is unlikely to be the cause for repeated fuse blowing.
     
  3. Svoy

    Svoy

    4
    0
    Jan 24, 2013
    Hi,
    Thank you for reply....
    So, I am going to test all the diods, but what about "the main switching mosfet"? Could you please tell me which one?


    [​IMG]
     
    Last edited: Jan 24, 2013
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Find out what the part number are on the devices on heatsinks 3 and 4
     
  5. Svoy

    Svoy

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    Jan 24, 2013
    Hi *steve* I really appreciate for your help....I found out the number on the devices on heatsink 4 its K10A60D and heatsink 3 K20A60U
     
    Last edited: Jan 24, 2013
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,363
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    Jan 21, 2010
    OK, a K10A60D is a 600V 10A mosfet. I would check the datasheed for that, and measure the resistance across the drain and source (both ways).

    And the K20A60D is a 600V 20A device. Check the same for this.

    Note that you need to ensure that the capacitors on the board are not holding a charge or you could (a) damage your meter, or (b) give yourself a very uncomfortable shock.

    Having two different devices like this seems to suggest that there are actually 2 independent power supplies on this board. Perhaps there is a standby as well as a main power supply, or perhaps the different voltages are on independent supplies?
     
  7. Svoy

    Svoy

    4
    0
    Jan 24, 2013
    Than you *steve* for your help....but after all I decided do not mess around with Power Supply for machine $2000 ....I just bought the new one....
    Thank you anyway
     
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