Learn How To Diagnose Power Supply Problems
The power supply converts your regular household current into low DC voltage used by the computer. When this component fails, there is simply no activity going on with your computer. Remember to do the easy troubleshooting first. Inspect the power supply for any damage. Double-check all connections.
Learning how to check your power supply and how to replace it when needed can be a lifesaver if you’re a computer buff or in business with the trusted PC. Don’t take for granted the simple pleasure of turning on your PC and everything works just fine.
We turned on one of our computers recently and in about one hour, it just rebooted itself. And it continued doing so about ten times a day until we found out the power supply was the culprit. Things to look for when your power supply is going bad or just dies on you:
No Power To The Computer
Here you must first check the wall outlet for power by connecting another device such as a radio or lamp to be sure power is present. If the computer is connected through a surge protector, check it as well.
If the wall out has power, check the power cable going to the PC to see if AC voltage is making its way to the system unit. Do this with the use of a multimeter.
If there is power, you will have to open the PC and check for power from the power supply to the motherboard.
When using a multimeter to check voltage, be sure you have a good ground for the black lead of the multimeter.
Rebooting Problems
One main problem you may face with an ailing power supply is that it may reboot the computer without any warning. All information is lost and it seems as though this happens at the worst possible time.
Booting errors when the computer first starts up may be another indicator of this component going on the blink.
Power Distribution Problems
When the power supply begins to fail, you may receive power at one device and not another. For example, the hard drive may receive power, but the CD-ROM drive has nothing at all.
Another headache that would cause rebooting is the intermittent power going to the drives or the motherboard itself. Follow the steps below to check your power supply should you experience some of the above problems.
Checking The Power Supply
If the wall outlet and the power cord are good, make sure the connection at the motherboard is secure. Then you may have to face the fact that the power supply itself is bad. If you have a multimeter, you can test the power supply output before purchasing a new one. Simply follow these steps:
- Turn off the PC, but do not unplug it. Open the system unit. Set the multimeter to read DC volts in the next range higher than 12 volts. Locate a power connector similar to the hard drive (or CD-ROM drive connector that is unused) and turn on the PC.
- You can also unplug a drive connector and use it. Turn on the PC and insert the BLACK probe into the power connector on one of the BLACK wires. Touch the RED probe to the YELLOW wire on the power connector.
- The multimeter reading should be +12 volts. Now touch the RED probe to the RED wire and the reading should be +5 volts. If no readings or different readings occurred, you’ll have to replace the power supply. If the readings were correct, you should check the P8 or P9 connectors at the motherboard. These connectors may also be named P4 and P5. To check these connectors, perform the following:
- Insert the BLACK probe into P8 at one of the BLACK wires. Insert the RED probe into the P8 connector at the RED wire. The reading on the multimeter should be +5 volts.
- Check the power going to the motherboard connections by inserting the RED probe into P8 at the YELLOW wire and you should get +12 volts. Leave the BLACK wire touching the BLACK wire at the P8 connector. Check the BLUE wire and the reading should be a -12 volts.
- Now move the BLACK probe to the BLACK wire on the P9 connector. Test the WHITE wire by inserting the RED probe and the reading should be -5 volts. Check the RED wires on the P9 connector and you should get +5 volts on each red wire. You won’t get exactly 5 or 12 volts, but the readings will be very close, such as 5.02 volts.
- If the Power Supply is a couple of volts off in either direction, such as when the RED wire should be reading -5 volts but it reads -8 volts, or if there are no readings, replace the power supply.
DO NOT remove the power supply from the system unit case when performing these tests. DO NOT perform these tests if you do not feel comfortable. Be sure to remove any and all electrical static build-up from your clothes and body BEFORE touching any parts inside the system unit. And NEVER open the power supply case for any reason, since high voltage may be present.
About The Author
Otis F. Cooper is solely dedicated to boosting the knowledge and confidence of every computer user that is serious about knowing computers. Use his informative articles and videos to understand every aspect about the PC. Read more about his formula for PC training here.
[Article Source: EzineArticles]
28 Comments
ali
December 7th, 2006
at 5:05pm
what if i dont have a multimeter . is there any other way round it.
Frank
February 14th, 2007
at 8:11am
Thanks this article helped me alot in school…
joseph mathew
March 18th, 2007
at 10:28am
Sir,
I have bestec pc smps using UC3842 ic.When switching on the fan will start ans stop.No output.I changed the ic still not solved.Can you help me in this.
regards,
CHANDRA
March 24th, 2007
at 5:29am
sir,
i need schematics to repair ATX PSU and solutions for common problems
thanks
Damien Service
April 18th, 2007
at 4:33am
My PC suffered the intermittent rebooting since November 2005 but I assumed it was the PC getting old.
Recently, I had to replace the power supply faceplate and then just a few days ago I decided to reinstall my PC and it went perfectly.
Other times programs wouldn’t work right and reading my software from my second hard disk where my downloaded software is stored would say there was an error with the installer and so forth.
Finding out now that my power supply faceplate was the problem certainly explained a lot and I am now thankful that I don’t need to buy a new computer.
warren empenida
May 16th, 2007
at 8:56pm
sir: this article really help me in my teachers guide…
Rudolph
May 24th, 2007
at 3:10am
Hello,
I want to ask how I can raise the load on my PSU.
It seems to be working fine but every two days I get a restart.
I am almost certain it’s the PSU. I want to raise the load and check whether or not it restarts more often.
Thank you in advance.
Neville
January 20th, 2008
at 11:21am
I have a weird problem ,I think its the Power Supply .For the past month I have had system crashes (new amd 4800 ) ,with power just dying on me for no apparent reason . Finally I tilted the cabinet to a horizontal position and it seems to work fine .I cannot understand this .Has any body experienced this ? .
MOHSIN
February 4th, 2008
at 4:06pm
I have a weird problem ,I think its the Power Supply .For the past month I have had system crashes (new amd 4800 ) ,with power just dying on me for no apparent reason . Finally I tilted the cabinet to a horizontal position and it seems to work fine .I cannot understand this .Has any body experienced this ? .
It will be due to some metallic dust on your mob, or it can be due to some faulty connectors such as IDE or Power cable.
DYLAN
February 15th, 2008
at 12:13am
For the past month my computer has kept restarting. After reading this article, I am almost convinced it is my Power Supply. I had just installed new ram (went from 512mb to 2gb) and a new video card (ATI Radeon 9550 128mb to a ATI Radeon X1650 Pro 512mb card). I only have a 350W PSU and i wanted to know if my PSU cannot handle these new components or is it just messed. I would also like to know what watt PSU should i get for a pc with the followign specs: Pentium 4 2.8ghz, 2gb ddr ram, Radeon X1650 Pro 512mb ddr2 video card
phillip
February 15th, 2008
at 10:12am
I started my pc, nothing, then 10 min later it booted up. next day started, nothing. after awhile it started smoking (no fans, no boot, just horrible electric smelling smoke). I opened it and the power supply was where the smoke came from. I replaced my power supply. hooked it all up, all fans working; those connected to mother board, power supply fans, case fans, etc. I can open and shut CD drives, and sounds like hard drives are spinning, even fan on my video card is whirling. However, monitor remains black. I heard 4 beeps when i started it up (once or twice of the many times I started it). Sound is on, but doesn’t sound like windows booted. I checked all the connections inside and out. I even tried another monitor and it also didn’t work.
What do I do?
Oat
March 1st, 2008
at 7:40pm
Excellent article. It helped my troubleshoot my PS and it’s fine so the problem I’ve been having has to be the Gigabyte MB.
Thanks.
Jeff
March 9th, 2008
at 5:52pm
Oat, what GB motherboard do you have and what is the problem you are having? I am having some issues with a GB motherboard too.
Linda
March 11th, 2008
at 2:44pm
My computer keeps burning up power supplies. I’m going on my 4th one in 3 months. The really wierd thing is that the computer that I replaced this one with did the same thing. I’ve had an electrician to my house to check things twice – the house is only 4 years old – and I’ve run extension cords to other rooms in the house to be sure it wasn’t the outlet the computer was plugged into. I bought a brand new ups power back up approx 2 months ago to make sure the power was clean. Me and my tech guy are at our wits ends trying to figure out what’s going on. I have two other computers in my house in different rooms and no problems with them. Anybody got any ideas??? Thanks in advance :-)!
Johnny
May 14th, 2008
at 8:06am
My computer won’t even turn on!! I’ve checked the wall outlet and the cable coming to the conmputer. They are fine. There is a light on the back of the power supply that is normally solid and when I plug in the power cord, it blinks. When I unplug the power supply from the motherboard, it is solid again. Can my motherboard be bad too? What else can I check to see what the issue is? Thanks.
Calvin Nabors
August 1st, 2008
at 7:37am
thanks for the informative article which helped me to test my power supply. I have a P4, 3.4 GHZ computer I use for video editing (Liquid Edition v. 7). On 7/31, it did not power on properly. I would hear the fans turning, but never heard the p.s. beep. Nothing was output to my monitor. Your article helped me test voltages, and determine that the PS was OK. Suspecting my video card, I removed it, then turned on my computer and heard the “beep”. At this point, I knew that my video card was faulty.
Confirm. New video card from Tiger Direct (ATI X1650 512M) and I’m back up and running.
I recommend that your article include the PS beep code information, and an isolation procedure, such as, remove peripherals one at a time to see if the problem goes away.
Thanks though for the value in this article!!
Stephen
August 15th, 2008
at 9:28pm
I seem to have power to my mobo because a little blue light. But I still get nothing no sounds or anything.could it still be my pay.
sb
September 5th, 2008
at 2:54pm
In regards to the article, each multimeter has speciffic error ranges, and if these are to big (and they often are with cheap multimeters), you will most likely get readings that are far from reality.
secreto
September 17th, 2008
at 1:28am
all problem is p4 computer. Computer always hang up or restart. if i internet didn’t hang if i play cabal or open media player they hang
vijai
September 22nd, 2008
at 11:40pm
I have a P4.i have a problem with my pc starting off.cabinet yellow color light not blowing.what to do?
but my pc fan rotating somewhat.
———-
vijai
sreevysh
sirclauss
October 17th, 2008
at 9:38pm
I work repairing and selling PC’s. I find that a lot of PSU’s are simply faulty. We RA a lot back to the supplier. I would say 1 in 30 fail easy. Also it depends on the brand. Yes we can have a PC come in with no graphics, we replace the PSU and things are fine. This is the fix in most cases. The slightest variance in voltages can avoid these things. I sometimes think ppl need to ask more questions of GOOGLE ‘cos a lot of answers are found via asking the “right” question. Cheers all.
Stall Vilbrun
December 9th, 2008
at 4:03pm
You guys Rock! Great Job and thanks.
Thor Asmund
January 17th, 2009
at 8:38pm
Dear Otis,
Thank you for this excellent article. I have had many broken PSUs in my life, and usually they die slowly. The +5V is off a little bit, or dips when a harddisk spins up etc.
But yesterday my PC died suddenly when I used my new Blue Ray DVD burner. After restarting it halted in the BIOS. After a couple of more retries it stopped saying DISK BOOT FAILURE. I knew it wasn’t a problem with my HD, so I searched the web and found your article which exactly describes my situation! Thanks to your detailed explanation I am now convinced I must have a broken PSU again. I will buy a new one tomorrow!
Thanks
In these cases, the problem might be in the Power Supply « Augustassps’ Weblog
August 21st, 2009
at 9:44am
[...] Basically, the yellow cable should give 12 V and the red one should give 5 V. There are a lot of article in the net about it. One is in this link. [...]
GEORGE
November 10th, 2009
at 6:33am
THE CHASIS OF MY COMPUTER IS ELECTRICALLY LIVE, THAT IS ONE GETS ELECTRIC SHOCK ON TOUCHING THE CHASIS. PLEASE WHAT WRONG WITH THE POWER UNIT?
chuck
November 11th, 2009
at 2:51am
i have a interesting issue here. most of the time i turn the computer on it starts and loads all programs no problem. once in awhile after it has been off for the evening i hit the start button and nothing happens sometimes i wait for a minute or 2 and it starts otherwise i literally have to unplug from my power strip wait afew seconds and plug it back in and it so far always starts again with no problems. the monitor is always on and the light is always blinking the printer also is enabled as well as the modem. it’s like “jumpstarting” the tower it works and has worked like this for months. a friend suggested it could be the power supply it very well could be i don’t know. have you heard of any problem that might resemble this. i have a dell 8250 using ati radeon 9800 pro with all the bells and whistles with a power supply the next step up to compensate for the fan on the card i guess. again this has only been happening the last 2 or 3 months. i’m guessing it’s probably 3+ years old on both. any help would be greatly appreciated thanx chuck c.r.cooper@comcast.net
benny
November 30th, 2009
at 3:00am
i need to know how power(current) is distributed in a motherboard that is start from where to where….
Ashok
December 4th, 2009
at 2:35am
Many thanks for your informing all of us about the Learn How To Diagnose Power Supply Problems.