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  1. #1
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    Default power supply fan erratic

    I have just replaced my burnt out cpu , which was an AMD athlon 2800+, it had a crack in it and my pc was dead.
    I obtained an AMD 2600 sempron, which i thought would get me up and running , if not a little slower.
    When i start up the pc, i get the normal sounds, all fans firing up, and the beep is single, the display is fine, and operation is ok.
    The problem is, that the power supply fan goes to full speed on start up, and drops down to its normal running speed, then races back up to the start up speed, and repeats this up and down constantly.
    It is hard to listen to this for more than a few minutes.
    I have exchanged the power supply, from another compatible pc and the same symptoms occur.
    Do you think the chip is incompatible with the MOBO... asus a7n266-vx. Sony pcv rs222.
    I know it's a bit of a dinosaur, but it's in mint condition, and i hate to skip stuff, when it can be fixed.

    Thanks
    Last edited by Ripsnort; 11-06-2009 at 12:22 PM.

  2. #2
    Member Digerati's Avatar
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    The CPU cracked? Never heard of that happening. I've heard of them being crushed by the user using too much force attaching the heat sink fan assembly, but not a CPU cracking out of the blue.

    My "guess" for the PSU fan (since this happened with 2 PSUs) is there a problem with the heat management system on the motherboard. Since it is not a requirement for the motherboard/BIOS to monitor or control the PSU fan, simply disconnect the PSU fan wire that is attached to the motherboard. If no PSU fan connection to the motherboard is used, then you may have two faulty PSUs.

    Do make sure your other fans are working properly, and the system is clean of heat trapping dust.
    Bill (AFE7Ret)
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    Quote Originally Posted by Digerati View Post
    The CPU cracked? Never heard of that happening. I've heard of them being crushed by the user using too much force attaching the heat sink fan assembly, but not a CPU cracking out of the blue.

    My "guess" for the PSU fan (since this happened with 2 PSUs) is there a problem with the heat management system on the motherboard. Since it is not a requirement for the motherboard/BIOS to monitor or control the PSU fan, simply disconnect the PSU fan wire that is attached to the motherboard. If no PSU fan connection to the motherboard is used, then you may have two faulty PSUs.

    Do make sure your other fans are working properly, and the system is clean of heat trapping dust.
    I know that both the psu's are good, have tested them on a running pc.
    I'm wondering what is the point of disconnecting the psu fan.
    It may be clear to you,but i'm afraid i don't get it. I'm not into pc tech stuff. Do you mean just running without a cooling fan , or can you disable the fan speed control wire ,and still have a running fan ?
    Thanks for the reply

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    Oh,and don't try and figure out the cracked chip. I gave the pc to a so called expert, i think he tried to fit the heat sink when the chip was not seated right.
    Cheers

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    Oh,and don't try and figure out the cracked chip. I gave the pc to a so called expert, i think he tried to fit the heat sink when the chip was not seated right.
    I've run in to way to many of those "so called" types before, sadly.

    I'm wondering what is the point of disconnecting the psu fan.

    It may be clear to you,but i'm afraid i don't get it. I'm not into pc tech stuff. Do you mean just running without a cooling fan , or can you disable the fan speed control wire ,and still have a running fan ?
    You are wise to ask for clarification. I absolutely DON'T mean to run without a fan! The PSU needs it's fan. Note that wire does not power the fan. In order to actually disconnect the PSU fan, you would have to open the PSU case - and that should only be done by a qualified (not "so called" ) technician because there are deadly voltages inside a PSU.

    You are on track with the fan speed control wire. That wire does 1 or 2 things, depending on the motherboard, and PSU's features. Most allow you to simply monitor the PSU fan's speed. Depending on the motherboard/BIOS and the PSU, it may also allow the system (motherboard and BIOS) to control the speed too. This speed control is not so much for heat control, but for noise control. With it disconnected, the fan runs at a constant full speed. Note that many PSUs do not even have that extra wire, instead relying on the PSU's internal sensors, rather than the motherboard's guesses.

    The idea of the PSU fan running at full speed may not "sound" appealing, but a constant drone would be better than listening to it speed up and slow down, speed up and slow down.

    So, just to make clear, disconnecting the small PSU fan wire from the motherboard IN NO WAY compromises cooling. My typical signature on these forums includes the line, Heat is the bane of all electronics! and I would include it here if allowed more lines.
    Bill (AFE7Ret)
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    Quote Originally Posted by Digerati View Post
    I've run in to way to many of those "so called" types before, sadly.

    You are wise to ask for clarification. I absolutely DON'T mean to run without a fan! The PSU needs it's fan. Note that wire does not power the fan. In order to actually disconnect the PSU fan, you would have to open the PSU case - and that should only be done by a qualified (not "so called" ) technician because there are deadly voltages inside a PSU.

    You are on track with the fan speed control wire. That wire does 1 or 2 things, depending on the motherboard, and PSU's features. Most allow you to simply monitor the PSU fan's speed. Depending on the motherboard/BIOS and the PSU, it may also allow the system (motherboard and BIOS) to control the speed too. This speed control is not so much for heat control, but for noise control. With it disconnected, the fan runs at a constant full speed. Note that many PSUs do not even have that extra wire, instead relying on the PSU's internal sensors, rather than the motherboard's guesses.

    The idea of the PSU fan running at full speed may not "sound" appealing, but a constant drone would be better than listening to it speed up and slow down, speed up and slow down.

    So, just to make clear, disconnecting the small PSU fan wire from the motherboard IN NO WAY compromises cooling. My typical signature on these forums includes the line, Heat is the bane of all electronics! and I would include it here if allowed more lines.
    Thanks for the clarification, i have alot more to go on , now.
    It's just annoying me what is the root cause, but i'll probably have to spend more than the pc is worth to isolate that. Thanks again for your information.
    Regards.. Paul

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    The root cause is probably a 10 cent sensor on the motherboard. You could start messing with BIOS settings or even flashing the BIOS, but that always opens up more possibilities for more problems.
    Bill (AFE7Ret)
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    Quote Originally Posted by Digerati View Post
    The root cause is probably a 10 cent sensor on the motherboard. You could start messing with BIOS settings or even flashing the BIOS, but that always opens up more possibilities for more problems.
    Thanks for the assistance, really appreciate it.
    I will stick with the basic stuff and manually hardwire the fan from another power source. If i bugger it up, then so be it.
    I'll keep you posted
    Regards


    Paul

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    I will stick with the basic stuff and manually hardwire the fan from another power source
    What? As I said above, the motherboard does not supply power to the power supply's fan - that is done internally to the power supply.
    Bill (AFE7Ret)
    Freedom is NOT Free!
    Heat is the bane of all electronics!
    MS MVP, 2007 - 2018
    ─────────────────────