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PC Won't Boot Up, PS-ON pin slightly below tolerance


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#1
yeschiro

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When I turn my computer on, it promptly powers back off (~5 sec). I hear the fans inside the computer turn on, see the lights on the front of the computer turn on, and then it will all stop. I don't see anything on the monitor and there is a single short beep coming from the computer before it shuts off by itself.

I manually checked the Power Supply, and all pins were within tolerance, but pin 14 (PS-ON) was just a hair below @ 11.38. Could this be enough to cause this problem?

Mobo:ASUS P5L-MX
PS: Allied SL-8360BTX

Edited by yeschiro, 09 March 2013 - 04:36 PM.

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#2
phillpower2

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Hello yeschiro

The single beep could mean that the CPU fan has failed and the beep is telling you that the MBs thermal sensor has shut down the system to prevent the CPU from frying or that you have a Ram or a video chip/card problem.

Testing a PSU with a multimeter is not conclusive as the PSU is not under load like it is when it has to supply all of the computers hardware, see my canned text below;

As a PSU puts out various voltages +3.3V, +5V and +12V it may appear that the PSU is working correctly but it is not, any significant drop of any output can prevent the system from booting up, the other scenario is a significant increase in the output which can be worse as it can fry one or more major components such as the MB, CPU, Ram, add on video card etc.
Please be aware that there are no user replaceable parts in a PSU so a bad one should be disposed of in a responsible manner and any type of conclusive testing will need to be done by a suitably trained Tech who has the required testing equipment and the relevant knowledge as to how to use it.


The +12V rail is only marginally low but that may change dramatically when the PSU is under load.

Do you have an add on video card or are you using the MBs integrated video chip.

How many sticks of Ram are fitted.
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#3
yeschiro

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Sorry for the delay.

Using the integrated video and both (2) RAM slots filled with 1 GB each.

If it matters, I had thought the fan was running "loudly" recently.
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#4
phillpower2

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No worries reply when you can as we all have other things going on and so understand :thumbsup:

It does sound as though the CPU fan may have problems and when they get noisy it is normally the bearings causing it.

I suggest a visual check is done by removing the side panel and powering the computer up to see if the fan is turning correctly, if it is not turn off the PC and post back.

Please do not at any time reach inside the case while the PC is on or while it is connected to the wall socket power outlet.
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#5
yeschiro

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Ok, I have most the weekend off to get to this. I hooked up the power supply to the MB only. I did not notice any issue with either fan. This is a video of the process and result.


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#6
phillpower2

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That sounds like either the blades on the CPU cooling fan are catching on the top of the heatsink or the PSU fan blades touching the PSU housing (this you should not check for safety reasons).

With all power and other cables disconnected from the computer check the CPU cooling fan for signs of play both left to right and up and down etc.

To see if it causes a change in the behavior once you have reconnected the video and other hardware remove the Ram and power up the machine and let us know if the beep code changes.

NB: Just so you are aware the Allied brand of PSU has a poor reputation so be prepared to replace it, some info http://www.10stripe....d/psu/brand.php and http://www.pcmech.co...ide-inside.html
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#7
yeschiro

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The CPU fan installed on the back of the unit felt like it has slight play. The one on the processor did not. I plugged in another fan from an old cpu but got the same response from the cpu.

Edited by yeschiro, 23 March 2013 - 03:28 PM.

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#8
phillpower2

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To see if it causes a change in the behavior once you have reconnected the video and other hardware remove the Ram and power up the machine and let us know if the beep code changes.

Did you try this and if so what was the outcome please.

Just a FYI: CPU = Central Processing Unit or in short the processor, the computer itself is referred to as a desktop or a tower in this instance.

Fans mounted on the chassis of the tower are referred to as case or system fans and not CPU fans, they often have a different amount of connection pins to that of a CPU cooling fan and many connect directly to the PSU itself by way of a 4 pin molex connection.

Other things that can cause this sort of behavior include a bad power button/case switch and a system short BTW.
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#9
yeschiro

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Yes, the beep code changes to 2 sets of long-short-short.

Is it normal for the computer to attempt to start immediately after plugging in the power cord? I do not need to press the power button. It just tries to start immediately after getting power.

Thanks for the vocab. My previous posts must have been a bit confusing...lol
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#10
phillpower2

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2 sets of long-short-short. = a video memory issue.

Is it normal for the computer to attempt to start immediately after plugging in the power cord?

No, this can be caused by a bad PSU, a broken power button/case switch or a system short.

Thanks for the vocab.

You are welcome :thumbsup:

I would check the power button first (while all power is disconnected) does it appear to be functioning correctly, you may be able to hear it click if it is ok.

Let us know what you find before we move on.
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#11
yeschiro

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Yes, I do hear a click when pressing the power button.
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#12
phillpower2

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The change in the beep code and the power button clicking as it would normally suggest that they may both be ok so next item to check is the PSU and the instant activation when being first plugged in.

Are you ok with removing the PSU from the case for testing purposes.
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#13
yeschiro

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Yes I am ok with that
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#14
phillpower2

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Sorry for the delayed reply - snowed under with work committments at present.

Please remove the PSU from the case, check that none of the PSU cables are in contact with each other, anything metallic or any other electrical components etc.

With the mains power cord connected to the PSU and the wall socket turn on the power at the wall outlet, does the PSU activate on it`s own.

NB: Not sure if your PSU has an on/off switch on the unit itself but if it does please ensure that it is in the on position for the test.
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#15
yeschiro

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I apologize for not getting back in a timely manner. I got buried myself.

THe PSU fan runs constantly with power. There is high pitched constant sound as well.
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