Help upgrading psu fan in a g4 mdd

Discussion in 'PowerPC Macs' started by groppo, May 24, 2015.

  1. groppo macrumors newbie

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    May 24, 2015
    #1
    Hi I recently received two powermac g4's and the fans are really loud, I know that this was a common issue and can be fixed by upgrading the fans. Would anyone recommend some silent fans for me that would work inside the psu?
     
  2. eyoungren macrumors P6

    eyoungren

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    #2
    Cooler Master, bGears, Noctua, SilenX are a few of the better known brands.
     
  3. groppo thread starter macrumors newbie

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    May 24, 2015
    #3
    I am worried about the airflow and voltages for the new fans so will any modern fan the same size work?
     
  4. eyoungren macrumors P6

    eyoungren

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    #4
    Yes, although you may have to fudge with connectors. Most modern fans are designed for PC logicboards. Some come with two or three pin connectors, some come with actual Molex connectors, but if there is an Apple proprietary connector none of them will come with that.

    I've had to splice a few, but I have replaced my PSU fan, my case fan and my small intake fan as well as added a 120mm fan in the bottom of my case (I drilled out a hole) and another 80mm fan blowing air directly on my video card. I've also got drive coolers on my hard drives.

    I've got a Quicksilver.

    In every instance I attempted to use a fan of the highest CFM I could find.
     
  5. groppo thread starter macrumors newbie

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    May 24, 2015
    #5
    I have opened my psu up it looks to have 2x 2pin 60mm fans now most fans i come across are 3 pin could i just use a 3 pin to 2 pin adapter as i know i have one about somewhere
     
  6. eyoungren macrumors P6

    eyoungren

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    #6
    Yes, but you don't necessarily need to. The three pin connectors are simply power, ground and speed sensing.

    If you plug the power and ground pins in correctly (assuming the connector has no protrusions in the wrong place) then the fan will power at full speed. The third pin is only necessary if you are intending to control speed.
     
  7. groppo thread starter macrumors newbie

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    May 24, 2015
    #7
    Ah thank you for the information, would you recommend a certain cfm and rpm for the psu?
     
  8. archtopshop macrumors regular

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    Dec 13, 2011
    #8
  9. groppo thread starter macrumors newbie

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    #9
  10. eyoungren macrumors P6

    eyoungren

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    #10
    I replaced my PSU fan with a bGears b-blaster 80mm fan. It's 62cfm.

    The connector for the old fan would not come off and I didn't feel like forcing anything and therbody damaging my only PSU, so I spliced the wires.

    That fan easily pumps out the most heat of all the fans in the case.

    http://www.newegg.com/Product/Product.aspx?Item=N82E16835132020
     
  11. groppo thread starter macrumors newbie

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    May 24, 2015
    #11
    thought the fans were 60mm how did you manage to fit 80mm?
     
  12. eyoungren macrumors P6

    eyoungren

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    #12
    Because my PSU is for a Quicksilver and therefore 80mm.

    Sorry, didn't realize the MDD's PSU fan was smaller.
     
  13. groppo thread starter macrumors newbie

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    May 24, 2015
    #13
    ah I see, well I have ordered some fans now thank you for all the help
     
  14. jbarley macrumors 68030

    jbarley

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    #14
    Please report back when you've completed the upgrade.
     
  15. groppo thread starter macrumors newbie

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    May 24, 2015
    #15
    will do, I had to import from the states so can be a few weeks now trying to decided on a 120mm fan :)
     
  16. tevion5 macrumors 68000

    tevion5

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    Ireland
    #16
  17. poiihy macrumors 68020

    poiihy

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    Aug 22, 2014
    #17
    You can reduce the speed of the fan by adding diodes on the red wire between the source and the fan. Diodes will lower the voltage and reduce the speed.
     
  18. LightBulbFun macrumors 6502a

    LightBulbFun

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    #18
    then overheat the thing needing to be cooled because the air flow was bad... (also diodes? a diode is used for rectifying AC to DC not dropping voltage...)
     
  19. poiihy macrumors 68020

    poiihy

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    Aug 22, 2014
    #19
    Well obviously you wouldn't make it too slow.

    I was surprised to heat diodes were good for reducing voltages but they actually are. Bunnspecial introduced the idea. Each diode has a certain step-down voltage so the voltage coming out through the diode would be x less than the input. And diodes output a consistent voltage and don't make heat (or not as much heat), whereas with resistors, the voltage drops as load is increased, and they make a lot of heat.

    But I cannot find bunnspecial's post and my reply about it.
     
  20. jbarley macrumors 68030

    jbarley

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    #20
    Diodes are commonly used to drop voltages in electronic circuits.
    I seem to recall each diode will lower the voltage about .2v, but this can vary a bit with the type of diode used.
     
  21. archtopshop macrumors regular

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    Dec 13, 2011
    #21
    The fan that you reference in the link doesn't put out the CFM to keep the power supply cool enough--not even close to the 38CFM of the originals. You'll cook your power supply in no time, in my opinion.

    The F126025DH delivers 32CFM, and would probably be ok. It would be much more quiet than the original; 31dBa vs 47dBa.
     

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