Solved PC won't post or boot

March 20, 2017 at 18:30:45
Specs: Windows 10, 8GB
When I press the power button, fans start then immediately stop, then start again, etc. Disconnected all peripherals but monitor, removed memory stick. No signal to monitor. When connected, hard drive starts then stops in time with the fans. It seems the PS is cycling on and off continuously.

See More: PC wont post or boot

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✔ Best Answer
March 21, 2017 at 20:40:30
List power supply make and model number or at least all ratings from label (Wattage plus amperage for each rail/voltage).
Try booting to the BIOS set up (Delete at power up), if it stays on then not hardware plus a chance (small) of finding out voltages in BIOS to see if within 5% of nominal values.
If you have another suitable power supply or can borrow someone's spare, try swapping out power supply and in 10 minutes you will know for sure if it is the power supply dying (very probable).

You have to be a little bit crazy to keep you from going insane.



#1
March 20, 2017 at 19:12:50
Any beeps? (have a speaker connected?)
Are you using a Graphic card?
Specs of you system? MB, CPU GPU etc

Clearing the CMOS/BIOS sometimes helps with POST problems. Remove coin battery or set dedicated switch/jumper. Make sure the AC is disconnected when you do anything inside the box.


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#2
March 20, 2017 at 20:36:29
Specs are important as well as whether this machine is new, recently built, or old. Has it worked before? Recently? Any recent problems prior to not starting?
Much more information is needed to help you.

You have to be a little bit crazy to keep you from going insane.


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#3
March 21, 2017 at 02:59:55
Your description (which includes an external monitor) inclines me to think this is a desktop system; which presuming so, it "might" be the actual on/ff switch - its internal contacts/tension spring failing...?

Do you have a volt meter, and if so are you comfortable going inside the case and checking the switch itself? Either check it does show volts "out" when closed/on. Equally, if possible, disconnect the switch and check its continuity when closed?

Alternatively connect a croc clip cable jumper across the switch terminals - to short-bypass them, and see if the system powers up ok that way?

message edited by trvlr


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#4
March 21, 2017 at 06:22:54
I've seen the described behavior on a computer of my own,
but it was so long ago that I don't remember what caused it
or how it got fixed or even which computer it was. I'm just
going to guess that your problem is *not* the power button.

How long does it take from pressing the power button to the
first shutdown? How long are successive on/off cycles?

-- Jeff, in Minneapolis


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#5
March 21, 2017 at 06:37:56
Verify the voltages from the PSU. My guess is one or more of the rails are slipping outside of tolerance.

How To Ask Questions The Smart Way


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#6
March 21, 2017 at 11:10:38
Thank you for your quick and excellent responses. I will try to answer all your questions and to provide maximum detail.
This very basic system is less than 3 years old; it was custom built with the following components:
Gigabyte GA-G41MT-S2P Mobo.
Intel Pentium Dual Core E5800,
4GB DDR3 RAM;
Seagate ST35004 500GB HDD;
Lite-on DVD Dual layer DVD;
no external GPU.
Last month it was upgraded to Windows 10 Pro with no problems. The case has never been opened until this problem. Computer has worked flawlessly until it would not boot.

I have tried various things: disconnected HDD, DVR, monitor, keyboard, mouse, removed RAM, removed CMOS battery and had only AC power connected.

The computer appears to start (blue led on switch turn on, fans run, led on DVR flashes) but then within 2 seconds, the blue led goes out, fans lose power for about a second or less then they all start up again to fade out as before. This goes on until I hold the power button in to shut down the computer. There are no beeps, the monitor registers No Signal. “Paper clip” test works.

Hope this info helps lead to a solution.


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#7
March 21, 2017 at 14:34:47
mmm Still could be the power on/off switch if it's a mechanical type; equally if it's actually an o/p amp style (i.e. a simple chip make/break as used on more than a few radios these days. I've known those behave exactly as you describe here).

But failing that then it does seem point to the psu... What is is its power rating and is it moe than just adequate for all the hardware involved?

Can you clip a volt meter across the psu o/ps to see what they're giving out, and it it's stable or not??

message edited by trvlr


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#8
March 21, 2017 at 17:54:08
It looks like an aging motherboard. (775 socket).
Possible one of the components on the motherboard gave up.

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#9
March 21, 2017 at 20:40:30
✔ Best Answer
List power supply make and model number or at least all ratings from label (Wattage plus amperage for each rail/voltage).
Try booting to the BIOS set up (Delete at power up), if it stays on then not hardware plus a chance (small) of finding out voltages in BIOS to see if within 5% of nominal values.
If you have another suitable power supply or can borrow someone's spare, try swapping out power supply and in 10 minutes you will know for sure if it is the power supply dying (very probable).

You have to be a little bit crazy to keep you from going insane.


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#10
March 22, 2017 at 15:19:18
Thanks for all your suggestions. It was the PSU and replacing it solved the problem.
This was the first time I came across a PSU that was partially failed and did't recognize the symptoms.
That's why these forums are so great!
Thanks again - problem solved.

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