Results 1 to 4 of 4

Thread: Rail voltages before starting pc

  1. #1
    Newbie
    Join Date
    Jun 2008
    Posts
    40

    Rail voltages before starting pc

    I'm having trouble starting my boat pc. I typically have to remove the bios jumper and replace the cmos battery to get it to start, after it has been sitting there a while without power. Normally, the pc will power up, with fans, but not post.

    Now, I'm not even getting to the power idle up phase. I'm getting the intermittent "on" signal (short) to the motherboard, but it is not powering up.

    I checked the rail voltages and the only one I see is 5V (No 12V or 3.3V). Also, the 4-pin to the motherboard does not have voltage.

    MY QUESTION IS:
    Should all the rail voltages be on after the 12V is connected or does the motherboard send a signal back to the m2-atx to enable the 12V and 3.3V? The +, -, and ignition voltages are all correct. Just trying to see if the motherboard is the problem or if it isn't starting because only the 5V is being supplied.

    Thanks,
    Marc

  2. #2
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    Location
    on the border of northern IL/IN
    Posts
    5,848
    i believe it does look for a 'life sign' from the motherboard-- where it shorts a signal wire to ground in the 20-pin harness.

  3. #3
    Constant Bitrate
    Join Date
    Feb 2007
    Location
    Taylorsville, UT
    Posts
    135
    Quote Originally Posted by soundman98 View Post
    i believe it does look for a 'life sign' from the motherboard-- where it shorts a signal wire to ground in the 20-pin harness.
    Its the green wire on the ATX connector, short that to ground and the PSU should turn all the rails on. Otherwise only the +5v standby should be on. Essentially when the M2 tells the mobo to turn on it shorts the two pins that should be connected to the on switch pins on the mobo, and that, in turn, will short the green wire to ground (any of the black wires).
    -James
    Car: 2004 GTI VR6 24v Turbo 2.8L, GT35R, 630cc, Unitronic, Bosch 044, etc, etc..
    Main PC:i7 920@4Ghz, 6GB DDR3, MSI X-58 Pro-E, Win 7 x64 RTM, Scythe Mugen2, 128GB G.Skill Falcon, 2x ATI4850 512MB Crossfire, Auzentech X-Fi Forte, Grado Labs SR-80

  4. #4
    Newbie
    Join Date
    Jun 2008
    Posts
    40
    Awesome. Thanks for the information.

Similar Threads

  1. Carputer starting, but not starting... frustrating!
    By GarryP in forum General Hardware Discussion
    Replies: 7
    Last Post: 09-10-2011, 10:22 AM
  2. ATX Voltages
    By bgelb in forum Power Supplies
    Replies: 4
    Last Post: 08-09-2002, 08:32 AM
  3. voltages
    By marsjell in forum Power Supplies
    Replies: 2
    Last Post: 06-03-2002, 11:04 AM
  4. Other Voltages from DC-DC PSU?
    By MrNiceguy in forum Power Supplies
    Replies: 7
    Last Post: 05-05-2001, 10:46 AM
  5. Strange PSU Voltages from DC-DC PSU
    By macphisto in forum General Hardware Discussion
    Replies: 6
    Last Post: 05-10-2000, 09:34 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •