iMac G3 power supply, unidentifiable component blown

Discussion in 'PowerPC Macs' started by stenstrop, Oct 29, 2018.

  1. stenstrop macrumors newbie

    Joined:
    Oct 29, 2018
    Location:
    Adelaide
    #1
    Hi all! I home this is the right place to post this.
    I got a working iMac G3 recently out of a recycling bin for free recently and it worked! at least for a while. After a few boots the power supply blew and it stopped working. I've taken it apart and found a blown ceramic capacitor. I would just look up the model of it and order a new one however, the label side is damaged and I can't make out the model.

    The capacitor is on the CRT power supply board and marked as "TH902" and socketed in "P903". The board part number is "6870T173D10", it's branded LG. I'll attach some pictures.
    IMG_20181030_152731.jpg
    IMG_20181030_152854.jpg IMG_20181030_152920.jpg
    If someone could identify this part I would love you forever!
     
  2. CooperBox, Oct 30, 2018
    Last edited: Oct 30, 2018

    CooperBox macrumors 65816

    CooperBox

    Joined:
    Nov 28, 2010
    Location:
    France - between Ricard & Absinthe
    #2
    I don't have an answer for you, but it may help others if you can state the exact model of iMac G3 you have and the processor GHz speed. The models range from iMac1 (M4984) through to PowerMac4,1 (M5521).
     
  3. stenstrop thread starter macrumors newbie

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    Oct 29, 2018
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    Adelaide
  4. philgxxd macrumors regular

    philgxxd

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    Feb 11, 2017
    Location:
    Malaga, Spain
    #4
    Can't help you much as I don't have that particularly model (iMac DV 400Mhz here) but that looks like a thermistor.
    It acts like a fuse so that it's socketed makes sense.
    I found it rather difficult to find a replacement for that kind of components as it looked to me they vary a lot but maybe some electronic expert could chime in.
     
  5. Eriamjh1138@DAN macrumors 6502a

    Eriamjh1138@DAN

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    Location:
    BFE, MI
    #5
    I think thats a transorb. Is the designator TH902 or P903?
     
  6. bobesch macrumors 65816

    bobesch

    Joined:
    Oct 21, 2015
    Location:
    Kiel, Germany
    #6
    A 333MHz fruit-color tray-loader with no fire-wire?
    If yes - at home I have the very same model in working condition and may take a picture of that black thing, but unfortunately not before the end of next week ...
     
  7. CooperBox macrumors 65816

    CooperBox

    Joined:
    Nov 28, 2010
    Location:
    France - between Ricard & Absinthe
    #7
    Whilst waiting for bobesch to get back to you, you could post your same query complete on the 'Apple Collectors' sister forum, or just the text, and link to your photos. On that particular forum, MacTech68 is extremely knowledgeable on a great deal of older Mac hardware, and may possibly have or know where to locate the schematic for that iMac.
    I note that he's not posted on this particualr forum since end 2015, but is a regular reader of the Apple Collectors forum and does post there regularly.
     
  8. stenstrop thread starter macrumors newbie

    Joined:
    Oct 29, 2018
    Location:
    Adelaide
    #8
    P903 is the socket (plug 903?) and TH902 is the component (Thermistor 902?)
    --- Post Merged, Nov 1, 2018 ---
    Yeah, that seems to be it! Thank you!
     
  9. bobesch macrumors 65816

    bobesch

    Joined:
    Oct 21, 2015
    Location:
    Kiel, Germany
    #9
    Today I had some time to tinker with my iMac and I read the official repair guide: for the first time I figured out, that getting access to the power-supply board does mean to expose the CRT-part of the iMac.
    I have to admit, that I have neither experience or courage nor the right equipment to get close to the high-voltage CRT, so I won't be able to give you support about that specific part of the power-supply board. I'm really sorry about that!
    (Especially because I've got a Strawberry-flavor iMac with probably also a defective power-supply board and I now recognized that I do not dare to even think about trying to open that relevant part of the iMac.
     
  10. stenstrop thread starter macrumors newbie

    Joined:
    Oct 29, 2018
    Location:
    Adelaide
    #10
    It's pretty easy to discharge the CRT https://www.wikihow.com/Discharge-a-CRT-Monitor If it has been off for a while (A few days) it should be perfectly safe.
     
  11. bobesch macrumors 65816

    bobesch

    Joined:
    Oct 21, 2015
    Location:
    Kiel, Germany
    #11
    Sorry, I won't try that ... The iMac and me we are both in a working condition yet :D and I don't want to put that on risk...
     
  12. ifrit05 macrumors regular

    ifrit05

    Joined:
    Dec 23, 2013
    Location:
    Near Detroit, MI. USA
    #12
    It's not risky at all. I have had to do this a ton of times for old Macs with CRTs.
    Just leave it unplugged for at least a day or two and you should be fine if you don't want to poke around the anode.
     

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11 October 29, 2018