My PC power supply randomly shuts down?
The power supply for my PC intermittently, and for no apparent reason, shuts down completely (no voltage on PS-ON). When this happens, if I immediately cycle the power switch on the power supply and then press the on/off switch, the computer starts normally. However, if this happens when I am away from the computer and everything has had time to cool, the above procedure does not work. When I attempt to start by using the above, the panel lights flash momentarily and the power supply shuts down again.
The only way to get
it to start is to run a hair drier into the power supply fan
for a few minutes, and then it will start. I don't think
that it is anything in the power supply that needs to be
warmed, but probably something else. I have disconnected
everything connected to the motherboard, but nothing makes
any difference. It would appear that the power supply is
bad, but this is not the case, as I have replaced it with a
known good unit, and the problem remains. I would certainly
appreciate any help.
Dave's Answer:
This is definitely not my area of expertise, so I asked my friend and colleague Jerry Foutz, who is a power supply guru, about your problem. Here's how he responded:
On my SMPS Tech Web site I present a general method of problem
solving. To solve any problem, you first have to know there is a problem,
that it is relevant, that it is solvable (preferably by you), and finally
what the solutions is.
Your reader certainly knows he has a problem and that it is relevant to
him, so the next step is the ask if it is solvable, preferably by him. The
approach he took, a good one, was asking help from a guru.
Is the problem solvable by a remote guru? The answer is no, with an
explanation.
The bottom line is that there is not enough information in the email, or
could there ever be, to solve the problem. Having said that, your reader
has shown remarkable troubleshooting skills. He has virtually eliminated
the power supply as the problem and isolated the problem to the load,
probably the mother board and its sensors. (A 90% probability SWAG, which
means there is still a 10% chance it is the power supply or one of the
motherboard plug in boards or a chassis mount component such as the fan.)
The power supply is probably doing what it was designed to do, protect
itself from a malfunctioning load.
And what do we know about motherboards? That they often have
"intermediates". Which are one of the toughest problems to isolate. A
frequent cause is a trace opens ups or shorts if the board is flexed or
changes temperature. And these are very tough to find, especially on a
multilayer board where all traces are not visible.
The only advice I can offer your reader is to do a very careful visual
inspection of the the mother-board or any other circuit board looking for
cracked traces, discolorization and any component that looks discolored or
in other than pristine condition, as I explain in my article on Troubleshooting Power Supplies.
This is a remarkably powerful technique.
What I have described is a systematic and logic way of finding the
problem. There are two others, finding someone who has had the same or
similar problem and hope they have a canned answer. Your reader had done
this and may have presented his problem on other venues. This is always
worth a try and sometimes works -- but don't hold your breath waiting for
an answer. The other is trial and error stabs in the dark. Again, don't
hold your breath.
The bottom line is, this problem is unsolvable by remote gurus like us.
Your reader has the mother board, eyes, and hopefully a multimeter to
check for opens and shorts. If he can't solve it this way he may have to
replace the mother board and other components and see if new components
solve the problem.
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Reader Comments To Date: 23
Another problem could be overheating. I know that 2 notebook computers I dealt with had this problem and would automatically shut off when it overheated as the fan was not working.
This is a problem I've had before. It's simply the result of an old, generic PS coming to the end of its life. As the PS' get older the electrolyte in the cheaper capacitors deteriorates to the point the PS cannot generate enough initial power to start the computer, without some coaxing, which is why the hair dryer technique worked. (Yes, I did the exact same thing with mine when this happened too.) And the reason it will randomly shut off is simply at some point there is too much drain put on the PS from the system, and it shuts down.
Only solution is a new PS. And investing in a good, name brand PS is ALWAYS a good decision.
An often overlooked and very easy potential fix is to replace the power cord. When replacing a power supply, it is often tempting to re-use the existing power cord since it is probably part of a tangled mess. An intermittent short or break in a power cord can often wreak havoc and cause unexplained problems.
Of course, his motherboard could have some of those defective, homemade capacitors that we've been hearing about lately. These tend to swell up and leak over time.
I was having this same problem while living with some friends over the summer. Occasionally my PC would shut off--as if the power plug were pulled from the wall. Eventually, I determined it was because my UPS was actually plugged into my friend's UPS (for lack of cable length I guess).
So my hypothesis was that the load of two PCs (and their monitors, sound, etc) was too much. Either that, or my UPS was bad (didn't get a chance to test that), OR, it just might not be a good idea to daisy-chain UPS connections. I found a way to plug directly into a powerstrip (bypassing all the UPSs) and problem solved!
P.S. I'm just now noticing that the date on this thread is 2005 not 2006. Well, I hope this helps someone out there who is searching for answers like I was anyway. I found this via Google in the first place. :-)
Thank you very much for your answer. It solved my problem. Tom :) 2006
What happens to my e-mail on gmail when the computer at the library shuts me off? Will it stay logged on? Can other people see my e-mail when this happens?
The problem i usually have is that,the defualt gateway am using for my internet always take time to start whenever there is power interuption.What is likely to be the problem.
Secondly,the printer am using in my office is connected to the network,but at times some poeple on the network find it difficult to print from their office.What can i do?
Thirdly,some of the computer in my office are very slow, what can i do?
My laptop is not turning on or charging the battery. The AC adaptor and the battery are good ( used another set). The jack was tested in there is no problem. When I plug in the adaptor supply voltage drops from 19V to 2.4V.The capacitor on the mtherboard DC-Dc supply looks good( not tested). Any suggestions?
hi i have problem with my pc? it does not start up when swicthed on, on light no power nothing. i have chaged the power supply, but that did not work; i need some help here. i have also disconnected all the cable to the motherboad; and then tried to see if that works. nothing reall happends; can you please help
Hello Dave,
I have a western digital 250 gig external hard drive it does not register or show what on harddrive when plug in USB (plug in and tried on three different computer). It dose not recoginze the hard drive however, when pull in and pull the device manager it does show the hard drive plug in. Can you assist
hi i have problem with my pc? it does not start up when swicthed on, on light no power nothing. i have chaged the power supply, but that did not work; i need some help here. i have also disconnected all the cable to the motherboad; and then tried to see if that works. nothing reall happends; can you please help.This is a new cry for help.
I have the same problem with my pc turning off after being on for awhile. It was my power suppply being clogged with dust. My pc is rather old and has bulging capacitors. The problem got worse over time as the pc turned off being on less time. I had a fan blowing at the pc and it helped to never turn off. I then cleaned the power supply and everything was fine for a week or two. It then repeated with the BS. It somehow damaged two dvd burners. I replaced the PS and it didn't help. I then bought some thermal paste and cleaned the heatsink and put the paste on. Still no help. I have narrowed it down to: i should have kept my pc clean and cool and allowed it to damage the capacitors to the point where only a fan blowing directly at the motherboard will help. Good luck
I have just had the same problem, after a while the pc shutdown.
after investigations it was due to the processor overheat this is due to either the collar is not attached well to the processor,or the motherboard overhaet setting is too low
My PC shuts down randomly too.
I have replaced the PSU, cleaned fans, re-applied paste between cpu and heat sync, removed devices, gaphics card etc and still not luck.
The only thing for sure is that it stays powered on ok if running windows xp in safe mode! I am using windows xp media centre service pack 3.
I've had the PC since 2006 , and its on basically 24/7 , I suspect I am going to need a new motherboard :-(
Brad from the very fact the system is stable on safe mode i think that the problem is more likely to be a software issue than a hardware one. In safe mode , device manager check for conflicts errors ect. try loading drivers individually. do you get BSOD before system powers down?
howdy my pc somtimes shuts itsself down and when i try to restat with power button it lights for a few seconds and stops again the only way to getr it running is to disconect the power supply and reconect a few times and then it will start and run fine it does this frequently and sometimes een when in stadby or frm fresh start hope you can help pls todd
hello anyone can solve my problem,i have a PC and ATX power supply 500w ,when i turn it on, it doesnt not take a long period a time ,it turned off awhile,.,please,any suggestions..?
Hi, i'm having problems with my power supply fan running down after start up, as normal, then back up to 3000, then down , then up. It does this continuously. Ramping up then dropping down.
I have recently renewed the motherboard,and cpu, as my pc was dead.Before it died the power supply fan was ok. Although the cpu is now a 2600 amd sempron, whereas before it was a 2800 amd athlon. I get the start up beep, and the pc functions fine. The cpu temperature is around 48 degrees centigrade, but this annoying fan keeps up and down. I can only access the bios to read, my pc is a sony rs222, with an asus mobo. I, am no tech wizard, but ok with a bit of instruction. Any ideas ? Thanks
I would like to respond to Todd Clark Jan 2009, I had the same problem exactly. It was the power supply. I replaced it.
I am an electronics engineer and I am looking into the failed supply out of curiosity only. It seems to relate to the LM339 IC in the power supply where the Power On signal goes to. It could be a shift in the comparator voltage or aged capacitors allowing too much noise or ripple as a previous contributor advised. They do fail and cause a range of problems. In earlier Power Supplies they would drop in value and prevent start up. I am still investigating but it is really NOT worth repairing and a LOT cheaper to replace the Power Supply. Good Luck
I have a Gateway Computer I bought new in 2002. The PC will not keep running. It will start up and run for 3-4 seconds and then shut down. It will not start up again unless I remove the power cord for 5 seconds and then replace. The PC will start but will only run for 3-4 seconds. Can you suggest possable problems.
Hi, I got a Dell XPS like four years ago for christmas. I spilt water on the laptop and it ruined the keyboard, so I hooked up another keyboard I bought to it and it works fine up until recently the laptop will shut off when it is on for only a few minutes or a day or so. What is the problem??? I am not good working with computers..So any help is GREATLY APPRECIATED!!
my aptop waqs nat able to open the operating system, the computer command said that, u have to log onn the usre profile, what should i do to open may operating system?
..my computer shuts off itself but i wonder that there is still lights in power button, and the power supply fan is not on.. and sometimes while i using my pc it unexpectedly display stop bluscreen error... total memory dump..
how can i fix it??
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I do have a lot to say, and questions of my own for that matter, but first I'd like to say thank you, Dave, for all your helpful information by
buying you a cup of coffee! |
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Another problem could be overheating. I know that 2 notebook computers I dealt with had this problem and would automatically shut off when it overheated as the fan was not working.