G4 MDD Power Supply Repair or small thin atx replacement????

Discussion in 'PowerPC Macs' started by ClassicII, Sep 26, 2009.

  1. macrumors 6502

    ClassicII

    Joined:
    Sep 21, 2009
    Location:
    Chicago, IL
    #1
    Hey Guys,

    I have a MDD quicksilver with a bad power supply. I have done some research and have found that the MDD psu does fail more than most. One of the biggest problem is cost. As most of you know replacements run $125 and up!!!

    What I would like to know is has any one found out what actually goes wrong in these psu's? With the amount that have failed I would guess it is a few components that are commonly going bad on each unit.

    If I cant figure out whats wrong with the unit, maybe a replacement?

    I have seen the standard atx power supply mod for the mdd but I was thinking something along the lines of the same form factor as the factory psu.

    Here is a few examples

    [​IMG]

    or

    [​IMG]

    Maybe the guts could fit in the factory psu enclosure with rewired new 24pin plug.

    Again I am just throwing this out there maybe some one all ready did this!! :)
     
  2. macrumors 68020

    gugucom

    Joined:
    May 21, 2009
    Location:
    Munich, Germany
    #2
  3. thread starter macrumors 6502

    ClassicII

    Joined:
    Sep 21, 2009
    Location:
    Chicago, IL
    #3
    That is what I'm talking about, we need an expert to find out whats going wrong with these units. If we can find a sole culprit maybe people can perform at home repair like the G5 Imac capacitor problem.
     
  4. macrumors newbie

    Joined:
    Oct 5, 2009
    #4
    Mdd Psu

    Let's keep this thread going... I need one too.
    I see on ebay, there is a user "TUSH" that repairs one at a time, but I never win the auction. I can't wait a week in between auctions for this BS... I just need someone to do a job.

    Any other ideas, folks?
     
  5. macrumors G4

    Joined:
    May 6, 2008
    #5
    Anyone know if the wiring is different from the PC versions (different pin-outs on the Main board connector)?

    The only thing I can recommend, is to see if you have any local electronic repair shops.

    Otherwise (without the confirmation of PSU pin-outs), you'd either have to deal with the auction based repair person, or get another one from a 3rd party source for Apple repair parts, such as macpalace.com.
     
  6. macrumors newbie

    karbon bee

    Joined:
    Oct 13, 2009
    Location:
    Canada
    #6
    Re: G4 MDD Power Supply Repair or small thin atx replacement????

    I found this reference (and similiar) below while searching power supply failure in a Digital Audio and then a Quicksilver - this seems applicable to all of the G4's since the Gigabit Ethernet was released - the only one seemingly not affected was the G4 Sawtooth. The link wasn't active when I just tried it, but I had copied and pasted the content for future reference when I first found it a while back.

    http://www.futurehardware.in/560903.htm

    "...I did discover that leaving the Gigabit-Ethernet and Digital Audio G4s plugged in and NOT turned on will kill the power supplies (thanks Apple). Seems that the 28 volt line (supplied to run the ADC-connected Apple Monitors) is being used by the motherboard when the computer isn't really on. The problem is that the power supply fan isn't on when the computer is off so the circuit board in the power supply cooks from the heat. Either unplug those G4s from the wall *OR* leave em on sleeping. Try this sometime, turn ON a Gigabit or Digital Audio G4 sometime when it's been off for a while and feel the temperature of the air leaving the power supply. It's pretty darn warm for the computer being off."​


    It would be interesting to know if any of you experiencing PSU failure in any of these models DID leave them turned off while still plugged into a live socket or powerbar on a regular basis. I leave strict instructions for mine, or those I've setup for others, to never be shut off unless unplugged or powerbar turned off - 2 years and counting for the oldest one with no problems yet (a 2000 Digital Audio).

    These links I had found about modding a general ATX PSU to use with these machines - there was a more specific one but I'm not able to find it right now. However these might help you out with the pin-outs (there are pictures). I did buy a kit on eBay (from a German Seller) called, "Adaptor ATX to G4 Power Supply 22 Pin DA Quicksilver" that was supposed to let me use a regular ATX PSU, but it was a waste of $40 + - the company did not help me trouble shoot the problem nor did they replace the kit as defective, so it was a total bust - might as well of spent the $80 on eBay buying a used psu for the quicksilver.

    Wiring up a G4 mobo is almost painless. Apple conveniently uses a 10 pin header with the same pinout across the G4 line up through the 'Quicksilver' machines...
    http://www.outofspec.com/frankenmac/wire.shtml

    How to convert a MDD Quicksilver power supply to let it work in any G4 (mainly Quicksilvers and Digital Audio's):
    http://www.xlr8yourmac.com/tips/MDD_ps_mods/MDD_PS_Mods.html

    ATX Power Supply Pin-outs:
    http://www.hardwarebook.info/ATX_Power_Supply

    Power Mac G4 (Gigabit Ethernet): Power Supply Voltage Test:
    http://docs.info.apple.com/article.html?artnum=95064

    Good luck.
     
  7. macrumors newbie

    karbon bee

    Joined:
    Oct 13, 2009
    Location:
    Canada
    #7
  8. macrumors newbie

    Joined:
    Oct 30, 2009
    #8
    Well, finding info on repair attempts isn't easy - I only found one report here on Macrumors:
    http://forums.macrumors.com/showthread.php?t=775638
    In this case the transformer was shorted.

    This evening I took apart mine, which is a Samsung 360W and found a blown component I couldn't really identify near the mains power inlet, in the section that has an extra grounded cover. It might be ceramic capacitor, but I'm not sure.

    I threw a few pictures into a folder:
    http://s17.photobucket.com/albums/b82/W_e_St/MDD/

    The exploded component is labeled TH2 (as far as I can read what is printed on the board with all that silicone) which seems to make a cap unlikely - on the other hand all the caps next to it look pretty much the same.

    The big question remains: are there other faulty parts, either parts that caused the failure or failed because of the heat?
     
  9. macrumors newbie

    Joined:
    Oct 30, 2009
    #9
    Ok, I asked some friends for help and played around with my DMM. The visibly blown part is a varistor and possibly it took out the big yellow capacitor next to it too. Not that it made much of a difference, since apparently a large part of the primary side was wiped out - the fuse is blown and at least one of the big MOSFETs reads a dead short.

    According to www.golytronic.de (German electronics repair shop with quite detailed info on those supplies) the Samsung MDD supplies tend to fail in such a catastrophic way and often even blow the house wiring breaker/fuse upon blowing up. Doesn't seem like an easy DIY repair, especially as the PCB is extremly densely packed.
     

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