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Power Source Problems

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#1 Guest_StaticID_*


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Posted 23 August 2010 - 09:43 AM


Iíve been having some weird hardware issues and a m8 recommends this forum for help!

So every few days my computer will freeze, or sometimes even a few days in a row, itís rather random.
I have ruled out RAM issues with Memtest and software problems by a complete reformat and reinstall of the OS.

The problem would seem to be the power source as when looking at the voltage with Hardware Monitor and SIW the +12v reading says...

Valve: 1.79v Min: 1.54v Max: 5.76v

Which is far lower than it should be : S

But when looking at the +12v voltage on the motherboard BIOS it is 12.032v, which is good!
I plan to swap the power source with my brothers when I next can to see if that helps.

But I am at a complete loss as to what is happening...
Has anyone encountered this problem or have some possible solutions to this?

My Specs...
Os: Windows 7 Ultimate 32 Bit (installed with update dvd)
Processor: Intel Core i5 750
Ram: 4 gb, 3.50 gb used
Motherboard: Gigabyte p55-ud3
Graphics card: ATI Radeon HD 4890
Power Source: Cooler Master Silent Pro 700w

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#2 dc3


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Posted 23 August 2010 - 10:11 AM

I've used SIW to check voltages before and have compared those reading to a DMM connected at the same time and was pleased to see that they matched. For that reason I'm a little concerned about the 12V rail of the PSU. The discrepancy could be because when the BIOS was being read there wasn't the usual load on the system where as the SIW reading would be real time operating temperatures.

Try using the following technique to test the PSU.

The purpose of this procedure is to bypass the motherboard to test a ATX PSU. Some manufacturers Like Dell have used some non ATX PSUs which have a different pinout for the 20/4 pin connector, please confirm that your PSU is a ATX type before using this procedure.

This procedure will involve working with live 12VDC electrical potentials which if handled improperly may lead to electrical shock. Proper precautions should also be taken to prevent electrostatic discharges (ESDs) within the case of the computer. For safety purposes please follow the instructions step by step.

First, shutdown your computer. Then unplug the power cable going into your computer.

Once you have opened the case, touch the metal of the case to discharge any static electricity.

The connector of the PSU which connects to the motherboard is readily recognizable by the number of wires in the bundle. To disconnect it you will need to press on the plastic clip to disengage it and then pull the connector up and away from the motherboard. Please take notice of the location of the locking tab and the notch on the socket of the motherboard, this will only connect one way as it is keyed. This wire bundle will have a memory of the way it has been installed and will want to bend back that direction, you may have to play around with it to find a position that the connector will stay in the same position while you run the test.

Posted Image

From the top left to right the pins are 13-24, the bottom from left to right are 1-12.

Please notice that there are PSUs with 24 pin and 20 pin connectors, the location of the green wire in the 24 pin connector is #16, and the green wire in the 20 pin connector is #14. If you look at the connector with socket side facing you and the clip on the top the number one pin will be on the bottom left corner. This makes the pin out for the 24 pin connector from left to right 13-24 on top, and 1-12 on the bottom. The pin out for the 20 pin connector from left to right is 11-20 on top , and 1-10 on the bottom. If you look at the connectors you notice that these are sockets that fit over the pins on the motherboard where the PSU cable attaches, this is where you will place the jumper. For a jumper you will need a piece of solid wire about the size of a paper clip (20-22 awg), preferably a wire with insulation. It will need to be large enough to fit firmly into the socket so that it will not need to be held in place while testing. You are at risk of electrical shock if you are holding the jumper when you power up the PSU. Insert one end of the jumper into the socket of the Green wire, and insert the other end into the socket of any Black wire.

Once the jumper is in place plug the cord back in. If the PSU is working properly the case fans, optical drives, hdds, and LEDs should power up and remain on. I would suggest that you not leave this connected any longer than is necessary for safety purposes.

At this point you can use a DC Voltmeter to read the different rail Voltages. You will want to insert the black probe into any of the Black (-) sockets, and insert the Red (+) probe in the five different colored sockets, one at a time. Below are the five different colors and their corresponding rail Voltages. The Voltages should be within about ten percent of the given values.

Yellow +12VDC

Blue -12VDC

Red +5VDC

White -5VDC

Orange +3.3VDC

To reconnect the 20/4 pin connector unplug the power cord, remove the jumper, and reconnect the connector. Take a moment at this time to make sure that nothing has been dislodged inside the case.

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#3 Baltboy


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Posted 23 August 2010 - 10:13 AM

My first thought whenever I hear random freezing is overheating. I would check all of the heatsinks and fans to ensure they are clean and dust free. Same goes for the power supply too. Could be the power supply or the motherboard failing as well since I have seen both. Replacing the PSU with a know good one is the best way to determine which one it is.
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#4 Guest_StaticID_*


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Posted 23 August 2010 - 12:17 PM

dc3 thanks for that very detailed reply! Its more help I've got in ages with this problem.
I will have to research the instructions and give this a try with some more computer literate m8's of mine.

My first thought whenever I hear random freezing is overheating. I would check all of the heatsinks and fans to ensure they are clean and dust free. Same goes for the power supply too. Could be the power supply or the motherboard failing as well since I have seen both. Replacing the PSU with a know good one is the best way to determine which one it is.

Yea, when I get access to it I may have to swap my brothers PSU with mine to see what happens. If the voltages are still low would that indicate that the motherboard is the issue?

ne how, i'll try these and post the results

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