wrong voltage after PSU change

Discussion in 'Hardware' started by stoxx4shortrun, Nov 4, 2009.

  1. My PSU fan stopped working probably a few months ago as I think it ran without fan for a while, an extra fan in the case made this possible without overheating.
    When I finally got round to changing the PSU this week, I first found out the new one had only 4 molex connectors and I needed 5, any way I managed to connect everything thanks to an extra connector on one of the unused connections in the case, I wasn't sure of what I was doing but all my devices work .

    Problem is Winbond Hardware Doctor, a monitoring software flashes an alert with the message that the "-5 V voltage exceeds the limit". Apparently it should be negative 4.5 max and it is positive at 3.5 !! I have no idea what this means despite asking around and looking up google.
    Been running the PC for 2 days like this but certainly something must be wrong and could cause problems.

    Any help ?
  2. in the modern era -5v is kaput i think
  3. It is likely that you hooked that particular connection backwards.
    -4.5 is the lower limit that the +3.3 or +5 supply is specified to tolerate.

    I can't think of anything that would ever require a negative supply.
    Go back and check the wiring.
    Actually, I take that back. Older bipolar transistor systems used dual supply, but I don't recall any modern CMOS computers using anything other than single supply. If your computer is relatively new, then it shouldn't need any neg supplies. Same argument still stands, I think one of your supply rails is connected backwards!
  4. Catoosa


    When you are sure the cables are connected, the voltages should be within 5% on their nominal to meet the standards that power supplies are manufactured to. Voltages that are not within the tolerance can cause file corruption resulting in operating system failure. I had a power supply that I knew was out of spec and it wiped out my operating system three times before I read about the power supply could be the cause. I changed the power supply, reinstalled the operating system, and all has been fine since.
  5. btw... as an additional diagnostic, you should go into your bios at startup. Most of the time, the bios software will tell you what the supplies are and which are specifically over under spec threshold.
  6. I disconnected the extra drive thus using only the 4 molex connectors provided, connected as they should be.
    I still get the same alert message. Now I contacted the manufacturer's support and here is their answer in broken english:

    Starting from ATX 2,01 the -5V rail is no longer prescribed. Thus this
    line is not to be found also with many power packs (manufacturers) no
    more. Now there is however the Main board K8N Diamond moon of MSI ore
    other, which must have this tension against the regulations. With the
    purchase of this Main board is to be paid attention thus before to the
    power pack, and/or differently. Therefore you look please in your Main
    board after manual whether this line are still needed.

    then when I said the PC was running fine, and had been in use for more than a week in that condition.

    when the PC works fine, than the board don't need this line.
    New Bords use the -12V Line.

    As a side note, if anyone knows a good monitoring software available for free, let me know. I think the one I use is old and might be the reason for these alert messages.