TechSpot

Should my -12v be giving less than 1 volt?

By kitty500cat
May 5, 2007
  1. My computer (a Compaq) has a 250 watt Bestec power supply. I think it might be giving some incorrect voltages.

    SpeedFan gives the following:

    VCORE: 1.58v
    +3.3v: 3.31v
    +5v: 5.05v
    +12v: 11.25v
    -12v: 0.72v
    -5v: 5.11v
    +5VSB: 5.40v
    VBAT: 3.25v

    I think that I've seen the VCORE at 1.6 volts already; I'm not sure what it's supposed to be. I think the -12v has fluctuated between 0.8v and 0.64v or lower. The low voltage of the -12v has me concerned; maybe it's being reported incorrectly or something. I usually keep my case fan at 100%; but the RPM fluctuates depending on how high the -12v is. When that voltage is lower, the RPM is lower as well.

    Should I be replacing my PSU? It is a Bestec, after all; but I've had this computer since September of '05, with no power-related problems yet.
     
  2. TangoTrolly

    TangoTrolly TS Rookie Posts: 59

    As you probably know, Bestec is not one of the better brands. Often used in eMachines, with a decent rate of failure. That does not mean they all fail.

    I suggest using a few different programs to measure temp, like: EVEREST or PC Wizard. Compare them with SpeedFan and see if they all show the same. Not all systems have a -12. Can't help you with that.
     
  3. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    ATX standard says that -12V has to be there! Maybe you mean -5V that was removed from the specification at ATX version 1.2? Of course, whether the actual motherboard makes use of this voltage or whether it has sensors or it, is a completely different matter.

    AFAIK the voltage tolerances are 5%, so your +12V and +5V are off limits too.
     
  4. kitty500cat

    kitty500cat TS Evangelist Topic Starter Posts: 2,154   +6

    I think that PC Wizard was maybe a few hundredths of a volt off on one or two of the lines, but nothing at all significant. I can't run Everest because I'm a part of a domain.

    Should I get a new PSU? Or would more info be helpful?
     
  5. howard_hopkinso

    howard_hopkinso TS Rookie Posts: 24,177   +19

    Hi kitty500cat.

    Those Bestec psu`s are absolute crap, I wouldn`t have one anywhere near my system. If I were you I`d seriously consider getting a better psu, before the Bestec fails and takes out some of your precious components.

    Psu`s by Antec/FSP/Enermax etc are all good brands.

    Regards Howard :)
     
  6. kitty500cat

    kitty500cat TS Evangelist Topic Starter Posts: 2,154   +6

    OK, thanks guys, I'll look into a new PSU.

    I'm looking at this. I like the fact that the efficiency is >80%. Is this a good/bad choice?
     
  7. TangoTrolly

    TangoTrolly TS Rookie Posts: 59

  8. wolfram

    wolfram TechSpot Paladin Posts: 1,967   +9

    Those FSP PSU's are excellent. I have a 400W ATX400-PA one, and it works excellent. They're highly recommended :)
     
  9. CMH

    CMH TechSpot Chancellor Posts: 2,039   +9

    Sorry, but I just gotta comment....

    -12V will definately give you less than 1 volt. Its negative :D
     
  10. kitty500cat

    kitty500cat TS Evangelist Topic Starter Posts: 2,154   +6

    OK, cool. I'm a noob at PSUs :D

    I think I'll get that one that TangoTrolly mentioned. Thanks, guys!

    Regards :)

    Edit: hey, it's ordered. I'll let you know how installing goes; I might need some help with that :blush:
     
  11. kitty500cat

    kitty500cat TS Evangelist Topic Starter Posts: 2,154   +6

    Update: installed it (the one TangoTrolly mentioned), works fine!

    Voltages don't really seem to be much, if any, better; but hey, I got that Bestec out of there.

    VCORE: 1.58v
    +3.3V: 3.33v
    +5V: 4.92v
    +12V: 10.88v
    -12V: 0.64v
    -5V: 5.11v
    +5VSB: 5.46v
    VBAT: 3.26v
    –all according to SpeedFan

    Thanks for all your help, guys; I'll let you know if I have any more problems.

    Regards :)
     
  12. wolfram

    wolfram TechSpot Paladin Posts: 1,967   +9

    Those voltages should be much better. Don't trust Speedfan's readings ;)
     
  13. kitty500cat

    kitty500cat TS Evangelist Topic Starter Posts: 2,154   +6

    The funny thing is, SpeedFan and PC Wizard agree completely :confused:
     
  14. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    What motherboard do you have? Maybe the mobo maker (or even HP) has some PC health utility that is able to read your motherboard sensors properly?
     
  15. captaincranky

    captaincranky TechSpot Addict Posts: 11,692   +1,879

    I Have the Concept, But Not The Color Code.....

    Sometimes I wonder if we don't rely too much on programs to do the grunt work.
    Any voltage on the power supply could be measured with a digital voltmeter, under load even. Since (generally)there are many extra output wires on the supply, all that needs to be done is to attach the (Red) + lead on the meter to whichever voltage you'd like to measure, while grounding the (black) - lead to the case. This isn't as radical or dangerous as it sound. To measure negative voltage either select the scale for - DC volts or (my favorite) ground the positive red meter lead and use the black to attach to the wire, and negative voltage will read as positive.
    What color is - 12 volts? No matter, old brain cells I'd probably forget tomorrow.

    I understand that you can't measure Vcore this way.
     
  16. kitty500cat

    kitty500cat TS Evangelist Topic Starter Posts: 2,154   +6

    Vcore is the CPU voltage (I think), so you can't really measure that.

    My motherboard is an ASUS, so I downloaded Asus Probe. It tells me the following:

    +12V: 11.52v
    +5V: 4.945v
    +3.3V: 3.328v
    VCORE: 1.534v

    So that's within bounds. Maybe I'll try using my multimeter to physically test the 12v and 5v lines.

    Regards :)
     
  17. captaincranky

    captaincranky TechSpot Addict Posts: 11,692   +1,879

    Roger That.....

    It is indeed, and no you can't.
     
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