Results 1 to 5 of 5

Thread: What is the significance of the -12 volt rail?

  1. #1
    Join Date
    Aug 2008
    Posts
    14
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Default What is the significance of the -12 volt rail?

    What is the significance of the -12 volt rail? It carries a voltage and has an amperage rating that is small, but what does it actually do?

  2. #2
    Join Date
    Oct 2006
    Location
    jonnyGURU forums, of course!
    Posts
    16,072
    Thanks Thanks Given 
    539
    Thanks Thanks Received 
    274
    Thanked in
    198 Posts

    Default

    The PCI slot has a -12V pin. Whether or not a particular card uses it or not and what it's used for depends on the card you have in the slot.

  3. #3
    Join Date
    Aug 2008
    Posts
    14
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Default

    ....this then is then is subject to the 5% to be within spec? (-12.6 volts seems a little high)

  4. #4
    Join Date
    Oct 2006
    Posts
    800
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Default

    Quote Originally Posted by Fossil View Post
    ....this then is then is subject to the 5% to be within spec? (-12.6 volts seems a little high)
    The -12V spec is +/-10%.

    AFAIK, there may be a very few old sound cards that use this.

    Specs: http://www.pcpower.com/downloads/EPS12VSpec2_91.pdf

    And yes I know there are several different ATX & EPS specs, but the -12V is still +/-10% regardless.

    Interesting is the fact that in some specs 0.0A is the minimum for the -12V rail.

    Dave
    Yes. One of the last commincations I had with Dave Hammock before he disappeared from the web was how a major brand single +12V rail PSU wasn't shutting down when shorted. We were literally arc welding with the PSU. Hopefully Dave's absense isn't due to the fact that he got over zealous with the welding.
    JonnyGURU Posted 4-1-08

  5. #5
    Join Date
    May 2008
    Location
    Beijing, China
    Posts
    2,376
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    7
    Thanked in
    4 Posts

    Default

    If your sound card uses both positive and negative 12V power on the OPAMP stage, the -12V ripple and noise affects sound quality. Many mid-to-high range PSUs uses a 7912 voltage regulator to generate -12V output, which is good for a clean output.
    It's been a hard day's night and I've been working like a dog.

Similar Threads

  1. Replies: 6
    Last Post: 10-27-2017, 09:19 AM
  2. Adding a large cap in series with 12 volt rail.
    By qismo in forum PC Power Supply Discussion
    Replies: 3
    Last Post: 07-22-2012, 11:10 AM
  3. +12 volt fluctuation?
    By Dave65 in forum PC Power Supply Discussion
    Replies: 5
    Last Post: 12-10-2010, 12:28 PM
  4. 7-Volt Mod Safe?
    By DuckieHo in forum PC Power Supply Discussion
    Replies: 5
    Last Post: 03-17-2008, 12:25 AM
  5. -6 Volt on the -5V-Rail ...?
    By TRJS in forum PC Power Supply Discussion
    Replies: 6
    Last Post: 10-29-2007, 02:12 PM

Posting Permissions

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