PSU Troubleshooting

I am troubleshooting an older psu before I go buy another one.


Random Shutdown's
Must unplug then plugin PSU to turn computer on after random shutdown's
Shutdown's occur at idle, high usage, and boot.

Computer History:

4 Years ago, Built computer from scratch.
2 Years ago, Replaced bad PSU
1 Year ago, Added HDD
4 Months ago, Rebuild due to failing memory (Caused computer to never reach post), New APU, Mobo, Memory, Monitor, Resulting in LESS Wattage requirements.
1 Month ago, Replaced FIRST HDD with 2TB HDD (Old drive was 3/gbs new is 6/gbs)

Current Build:

AMD A8 3850 Llano APU
450w 2 year old PSU. (Purchased new at store)
2 x 2GB DDR3 1600 memory UNDERCLOCKED to 1333 (BIOS Default)
160GB SATA2 7200RPM HDD (Purchased used at store)
5 USB Devices (WebCam, Printer, Mouse, KB, Occasional PS3 Controller)


Current 450w PSU is acceptable for equipment/hardware/peripherals being ran. (Recommended
PSU Wattage: 279w + 10% + 20w = 326.9)
APU is at an acceptable 30C at time of shutdowns.
MOBO Caps are good.
CMOS reset did not help.

PSU Voltages:

Anyone else see anything odd with these results? How is my computer even on?

Posting this from the computer with these issues.

Running a PSU Test with OCCT causes a shutdown.
At the time of this posting I will run another OCCT PSU Test and see if it fails.
5 answers Last reply
More about troubleshooting
  1. PSU Test Passed, No shutdown.
  2. If your voltae readings were taken while under load your PSU is weak at best. I'd replace it with a significantly larger one. Look at Seasonics.
  3. Im on a VERY low budget and would rather not replace the PSU to have my rig shut down again because it was something else.

    Can someone please list troubleshooting steps that do not require the replacement of the PSU and possible ways to see what is causing the random shut offs.

    Its not from high load, it happens even in bios. (Not software related).

    Case is clean and there are no shorts.

    Computer is connected to a surge protector.

    Noted 12v rail getting low under extended load. Could this be the culprit?
  4. Does the computer shutdown out of the blue with no warning or error message's ? With the symptoms of intermittent shutdowns during idle,load and booting it does sound like your typical PSU problem. It's very common during a build for the PSU to be overlooked but when in fact it's actually a very important part not to cheap out on which brings me to my next question: What brand power supply is it ?

    Unfortunately trying to determine if a power supply is bad and going off voltage readings via software is unreliable. The proper way to troubleshoot it is with a digital multimeter(DMM) if you have one and if you don't they are relativity cheap to purchase.
  5. The ATX Power Supply Design Guide states the following specification tolerances:

    DC Output Voltage Regulation

    +12V Range ±5%
    Min.: +11.40 Volts
    Nom.: +12.00 Volts
    Max.: +12.60 Volts

    +5VSB Range ±5% <--- this is also known as +5V VCCH
    Min.: +4.75 Volts
    Nom.: +5.00 Volts
    Max.: +5.25 Volts

    If your readings can be trusted, for these two rails, they are considered out of spec and it will cause problems.
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