PSU voltage fluctuations....

By Greenmachine
Jun 12, 2006
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  1. Okay well I recently bought an ASUS 6600 256MB AGP video card. After about a week or so I decided to upgrade my PSU as well. I purchased the Antec SmartPower 500W. My Asus SmartDoctor program (that monitors voltages, temps, & fan speeds) keeps warning me that the AGP chipset is not supplied with enough voltage. It is not a constant warning. It will warn me and then a second later it will say that "my video card is OK." I have been watching the levels and they will remain constant for 10 mins. or so and then all of a sudden the "Vcore" voltage will jump. Sometimes the Vcore voltage goes to zero and sometimes it goes above the recommended level. I am not sure what it could be. If it is a defective PSU or what. Any ideas???
    Cheers
  2. KingCody

    KingCody TechSpot Guru Posts: 1,568   +7

    use another program to monitor voltage (like speedfan or MM5). if your vcore dropped to zero, your CPU would not work.

    Antec makes very good quality power supplies, while anything is possible it is unlikely to be a faulty PSU. while the smartpower series are the budget end of Antec's lineup, they are still good power supplies and have reliable over-voltage protection circuits.
  3. iss

    iss TechSpot Chancellor Posts: 2,896

    I agree with kingCody, try another program incase the asus program is reporting false readings. if another program reports out of range readings then I would contact Antec for a replacement PSU.
  4. Greenmachine

    Greenmachine Newcomer, in training Topic Starter Posts: 164

    Okay...well I used speedfan last night. I let it run all night long and when I woke up here is what I got:
    +5V min=1.51 max=6.18 mean=3.31
    +5V min=1.42 max=5.97 mean=3.07
    +12V min=11.90 max=12.16 mean=12.03

    Those were the only values that were off by a significant amount. What is the deal with two +5V readings? There is definitely something wrong on the 5V though. from 1.51 to 6.18 =yikes. Does not seem very stable to me. My comp also freezed up last night while playing Halo. It has never done that before, not even with my 300W psu and the 6600 vid card.

    Any suggestions???
    Cheers
  5. KingCody

    KingCody TechSpot Guru Posts: 1,568   +7

    there is one +5V, one -5V, and one +5VSB. the 5VSB is the standby voltage that stays on when your computer is powered off "waiting" to be turned back on.

    the +5v should stay right about 5V, go into your BIOS and watch your voltages there for a bit. if you have a multimeter, read it with that.

    if you see something odd or it fluctuates, then RMA your power supply.
  6. Greenmachine

    Greenmachine Newcomer, in training Topic Starter Posts: 164

    In my BIOS there is not a voltage read out, at least not that I have seen. I get fan speeds and temps, but next to the voltages all it says is "OK." Would only a defective PSU make the +5V rail jump all over like that??
  7. KingCody

    KingCody TechSpot Guru Posts: 1,568   +7

    if that is the actual voltage and not just inaccurate software, then yes the PSU itself would be the only culprit.

    it is still likely to simply be bad voltage computation on speedfan's part. i would imagine that your computer would be acting up with voltage fluctuations as extreme as that. but the only way to know for sure is to measure the voltage from hardware, not software.

    use a standard digital multimeter. take an unused 4 pin molex connector and measure from the red and black wires (the red wire is +5v, the yellow wire is +12v, and the two black wires are both ground).

    antec smartpower voltage regulation
    this means that the +5v rail should be no more than .25v + or - (+4.75v to +5.25v)
  8. Greenmachine

    Greenmachine Newcomer, in training Topic Starter Posts: 164

    Unfortunately I do not have a multimeter....should I take my comp in and get it checked?? My speedfan worked fine with my other PSU. My old CompUSA 300W PSU only had a minor drop on the 12V rail. I will upload a pic of my speed fan voltages. Here is a pic of just after five minutes or so....

    Attached Files:

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