Strange PSU behaviour with 2 SSDs

Discussion in 'Mac Pro' started by Akira28.com, Dec 10, 2013.

  1. Akira28.com macrumors member

    Joined:
    Oct 2, 2013
    #1
    I'm on MacPro 5.1 with GTX Titan.. Since i bought an external PSU for the Tity, i decided to use it for my SSD too..
    The PSU is an OCZ ZT 750 W.. I used the paperclip trick between the 4th and 5th pin (green and black) to let it power on without mobo and it all worked great..

    Then I just got my second SSD and things became absurd.
    When i plug both SSD the PSU powers on and then shuts off!
    What I tried to do to verify (i have 3 sata cables, each has 3 connectors)(i made this try with the Mac off, so the whole power was available):

    - Plug one SSD per time (one cable, one connector). OK
    - Plug one SSD on a rail and one on another (2 cables). SHUTS OFF
    - Plug both SSDs on the same rail (one cable, 2 connectors). SHUTS OFF
    - Changing cables and repeating these 3 points. SHUTS OFF
    - Changing rails and repeating these 4 points. SHUTS OFF
    - Using a Y sata splitter from a connector of one cable (one cable, one connector). SHUTS OFF

    I tought one of the 2 SSDs could be faulty, but they seemed ok when put in the same working condition.
    The OCZ shuts off when he has 2 SSDs connected, no matter on which cable or connector or rail.
    It looks like when he has to power more than a SSDs he dies.

    Faulty PSU? What do you think?
     
  2. willgreene99 macrumors regular

    willgreene99

    Joined:
    Dec 16, 2010
    Location:
    DFW
    #2
    Although it does appear to be a faulty PSU, it may be difficult to diagnose unless you are able to send it back to them for repairs or replacement.

    You may want to do it soon as I read they filed for bankruptcy and their support may be not the same as it was before.
     
  3. OrangeSVTguy macrumors 601

    OrangeSVTguy

    Joined:
    Sep 16, 2007
    Location:
    Northeastern Ohio
    #3
    That power supply is kinda overkill anyways for just a single Titan.
     
  4. Akira28.com thread starter macrumors member

    Joined:
    Oct 2, 2013
    #4
    I know, but the idea was to have the way to eventually connect another GPU.
    It has 4 pcie cables and it's one of the best quality/price ratio PSU. Not so many PSUs has 4 pcie cables
     
  5. westrock2000 macrumors 6502

    Joined:
    Oct 18, 2013
    #5
    The SSD's will be drawing from the 5V rail, while the video card pulls from the 12V.

    So it is entirely possible that the PSU could have a bad 5V section but be unaffected when powering the video card.

    Do you have any other hard drives you can plug into it just for correlation?
     
  6. Akira28.com thread starter macrumors member

    Joined:
    Oct 2, 2013
    #6
    Yep, i know they are on different rails.
    But il looks like the problem is on the 5V.

    I'll try with some hard disk instead of the second SSD
     
  7. Gav Mack macrumors 68020

    Gav Mack

    Joined:
    Jun 15, 2008
    Location:
    Sagittarius A*
    #7
    I would keep any external PSU designed primarily for graphics cards away from powering hard drives. The supply using doublers and long power cables from the optical bays is more than sufficient.
     
  8. Akira28.com thread starter macrumors member

    Joined:
    Oct 2, 2013
    #8
    I was using the PSU because i don't have to run cables all through the mac
     
  9. Gav Mack macrumors 68020

    Gav Mack

    Joined:
    Jun 15, 2008
    Location:
    Sagittarius A*
    #9
    I know its a little bit more hassle but the cables cost about 10-15 bucks. Once done never have a need to run another.
     
  10. westrock2000 macrumors 6502

    Joined:
    Oct 18, 2013
    #10
    He's using a standard PSU, using a paperclip on pin 16 of the motherboard's 24 pin harness.
     
  11. Akira28.com thread starter macrumors member

    Joined:
    Oct 2, 2013
    #11
    Precisely.
    GPU and SSDs.
     

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