Power source only gives 3V

Posted on 2004-11-27
Last Modified: 2010-04-25
Hi, first of all I want to apologize for my English.
I have bought a computer about three months ago and it has given me one headache after another.
motherboard: Asus A7V8X-X
processor: Athlon XP 2400+
512 Mb RAM
video card Nvidia FX-5500

It has a 400 W power source. I ran Asus PC Probe and noticed that it was not giving 3.3 V but only about 3.0. And it was giving 12.5, not 12.
Today the computer would not boot up, so I called a technician and he saw that there was a problem with the 3.3 cable. He lent me another power source and it is working, but PC Probe is still showing 3.0 V
a. Is this a problem?
b. Can it be a motherboard problem? Could the motherboard cause the source to fail?
Question by:clau
    LVL 8

    Accepted Solution

    On my nforce2 board (EPOX) all monitors reports the 3,3 volt as 2.7 volts I did a lot of digging into this and found out that it was my Vdimm(ram) that was reported as 3,3 volts.

    If you have access to a voltmeter simply measure the voltage between and orange wire(on top of my head) and a black wire

    ATX spec says all tolerances is +/- 5% except 12volt where +/-10%

    So 12.5 is ok but 3.0 is not

    HAve you tried inspecting those values in the BIOS ?

    And yes theoretically a motherboard in case of shorting or malfunctioning can "cause the source to fail"

    LVL 31

    Expert Comment

    If it runs OK, it may be unimportant. A too low voltage doesn't sound dangerous to me. Besides, these on-board voltage probes, anyone knows how accurate they are? If you are concerned about this, make sure you check the reading with a proper meter.

    Author Comment

    Some more info:
    Today I tried the new power supply in another computer and it gives the 3.3V OK.
    I am reading the info from the hardware monitor in the BIOS setup.
    The new computer does have problems: it freezes, I had to use a USB keyboard because PS2 ones stop responding, I had to install Windows 98 because I had trouble with the video card drivers in Win XP, etc.
    Tomorrow I will try another one

    Author Comment

    Well, I did many tests and:
    a) tried 2 DIMMs 256 Mb each DDR333 instead of my DDR400 PC3200 512 Mb DIMM - same result
    b) tried a GeForce 440 64Mb RAM and the power supply gave 3.1V
    c) tried a 450 W power supply and it gave 3.3V

    So, my conclusion is that there is something in the motherboard that is eating too much power.

    Maybe it is a faulty mobo? Or is it a feature?
    Is there a way to verify this?
    Stockhes, how can I find out if I have the same RAM problem than you?
    LVL 87

    Expert Comment


    No comment has been added to this question in more than 21 days, so it is now classified as abandoned..
    I will leave the following recommendation for this question in the Cleanup topic area:
    Accept: stockhes

    Any objections should be posted here in the next 4 days. After that time, the question will be closed.

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