Computer does random restarts after putting in a 350 watt PSU

Some of the important background for this post is in Computer gets power, shuts off, gets power, repeats, never boots from late 2011.

But in quick form, I have a decent home-built computer that last year had the Gigabyte motherboard go bad, take the processor with it, and a new Gigabyte MB and Intel I3 processor were put in after a lot of trial and error, and I was back in business.

For 12 months anyway.

Last week, I turned the computer on and the lights and fan came on for a couple seconds, then it turned off. Turned it on again, and the lights and fan came on and stayed on, but no POST, no boot, nothing.

Took it to a really great repair shop who fixed me up last year and in an hour they'd called me to say it just needed a new power supply. "We've got you running, and you're all set."

My old PSU had been a 400 watt Corsair. This one was a 350 watt, not sure of the brand, but this repair shop doesn't deal in junk, so I assume it was a decent brand. They said that I could keep the 350 watt one, which was $25, or they had 500 watt ones that would cost quite a bit more, but that 350 should be fine.

Got the computer home, connected it, powered up, all good - and then after about 2 1/2 hours, boom, screen went black, and it went through a restart cycle. Ten minutes later, same thing.

A check of the event viewer showed that there had been no errors or critical events until yesterday morning at the repair place, when presumably they powered it up with all the peripherals disconnected from the PSU. Then there was a "kernel-power" error (I'm not on that computer now, so could be "off" in my description) associated with each restart.

I let the computer run without restarting when I went to bed. This morning it was at a login screen, meaning it had restarted. Checking the event viewer, there were kernel power errors at:

• 8:36 pm
• 8:42 pm
• 11:46 pm
• 11:55 pm
• 12:12 am
• 3:06 am

And then I used it for about half an hour at 7 am without problems, and powered it down and disconnected it. Note that the final three restarts occurred from the login screen, since it restarted to the login screen.

After the first two restarts, I fixed "startup and recovery" from the system properties to NOT restart after a system failure and yet, clearly, it was restarting each time, otherwise we'd not have been on the login screen, with events logged.

The computer is back at the shop, but I'm looking for some insight from users here about what could be wrong.

My theories:

• The replacement power supply, at 350 watts vs. 400 before, is inadequate. I'm not quite comfortable saying this is the case though, because I used several online "power supply calculators" and all said based on my hardware profile, 299-325 watts should do the trick.
• I have some underlying issues in my motherboard. Again, my computer worked perfectly from 12/2011 until 12/29/2012, but maybe my MB is spotty and the actual driver of the computer failing to start last week, then sporadically restarting this week?
• Last year, when the computer was bad, I swapped my son's computer in for mine. When I attached the power cord to my son's computer, and powered it up, it did not turn on until I moved the cord to another port on the power strip, and that has always bothered me since. The power cord is from 5+ years ago, and has had different computers connected to it - it stays plugged into the power source, and reconnected to whatever computer I'm using there. Could the behavior I've described be caused by a flaky power cord?

I'll welcome insight from readers about this.

And what should I expect from the shop? Since the computer basically has not run without flaw for more than four hours since this started, I guess I should expect them to keep it running for at least four hours before taking it back, and if I have a problem then, check if it's the power cord.

450125 said:

Some of the important background for this post is in Computer gets power, shuts off, gets power, repeats, never boots from late 2011.

But in quick form, I have a decent home-built computer that last year had the Gigabyte motherboard go bad, take the processor with it, and a new Gigabyte MB and Intel I3 processor were put in after a lot of trial and error, and I was back in business.

For 12 months anyway.

Last week, I turned the computer on and the lights and fan came on for a couple seconds, then it turned off. Turned it on again, and the lights and fan came on and stayed on, but no POST, no boot, nothing.

Took it to a really great repair shop who fixed me up last year and in an hour they'd called me to say it just needed a new power supply. "We've got you running, and you're all set."

My old PSU had been a 400 watt Corsair. This one was a 350 watt, not sure of the brand, but this repair shop doesn't deal in junk, so I assume it was a decent brand. They said that I could keep the 350 watt one, which was $25, or they had 500 watt ones that would cost quite a bit more, but that 350 should be fine.

Got the computer home, connected it, powered up, all good - and then after about 2 1/2 hours, boom, screen went black, and it went through a restart cycle. Ten minutes later, same thing.

A check of the event viewer showed that there had been no errors or critical events until yesterday morning at the repair place, when presumably they powered it up with all the peripherals disconnected from the PSU. Then there was a "kernel-power" error (I'm not on that computer now, so could be "off" in my description) associated with each restart.

I let the computer run without restarting when I went to bed. This morning it was at a login screen, meaning it had restarted. Checking the event viewer, there were kernel power errors at:

• 8:36 pm
• 8:42 pm
• 11:46 pm
• 11:55 pm
• 12:12 am
• 3:06 am

And then I used it for about half an hour at 7 am without problems, and powered it down and disconnected it. Note that the final three restarts occurred from the login screen, since it restarted to the login screen.

After the first two restarts, I fixed "startup and recovery" from the system properties to NOT restart after a system failure and yet, clearly, it was restarting each time, otherwise we'd not have been on the login screen, with events logged.

The computer is back at the shop, but I'm looking for some insight from users here about what could be wrong.

My theories:

• The replacement power supply, at 350 watts vs. 400 before, is inadequate. I'm not quite comfortable saying this is the case though, because I used several online "power supply calculators" and all said based on my hardware profile, 299-325 watts should do the trick.
• I have some underlying issues in my motherboard. Again, my computer worked perfectly from 12/2011 until 12/29/2012, but maybe my MB is spotty and the actual driver of the computer failing to start last week, then sporadically restarting this week?
• Last year, when the computer was bad, I swapped my son's computer in for mine. When I attached the power cord to my son's computer, and powered it up, it did not turn on until I moved the cord to another port on the power strip, and that has always bothered me since. The power cord is from 5+ years ago, and has had different computers connected to it - it stays plugged into the power source, and reconnected to whatever computer I'm using there. Could the behavior I've described be caused by a flaky power cord?

I'll welcome insight from readers about this.

And what should I expect from the shop? Since the computer basically has not run without flaw for more than four hours since this started, I guess I should expect them to keep it running for at least four hours before taking it back, and if I have a problem then, check if it's the power cord.

You state the computer shop doesn't deal in junk, so I presume you feel they are not a shoddy shop and are competent. Nobody who replies to you in this forum is going have more knowledge about your particular computer then they will and I am sure they can provide details regarding your general questions as well. My question; why not ask them the questions you posted?

Sir George said:

You state the computer shop doesn't deal in junk, so I presume you feel they are not a shoddy shop and are competent. Nobody who replies to you in this forum is going have more knowledge about your particular computer then they will and I am sure they can provide details regarding your general questions as well. My question; why not ask them the questions you posted?

That's a good and fair question.

My two reasons are that, first, someone here might have an "angle" or question for me to raise with the repair people that I'd not thought of. And second, the repair shop might have dealt with several dozen, maximum, users with problems close to what I describe. But here, in this forum, in a post it might have taken me 20 minutes to type, likely more than several dozen people who've had similar experiences will read and some will share. A valuable resource to tap into.

And a third reason: On occasion, when I've had a repair problem, computer or otherwise, I've started a thread in a forum, and then shared the link to the person doing the repair, so that things are explained in thorough detail, and in writing.

I would too go with the inadequate power supply theory. I had the same problem once, and the way you are experiencing the symptoms sounds very familiar.

Apart from factoring in a bit of headroom as Thorsen stated, you also need to consider that the Watt values given by the PSU manufacturer are peak values. Depending on the quality of the PSU, it won't work reliably if it is constantly running at or near capacity. Back when I had those problems, I had a 700W PSU from a very cheap manufacturer, in a system that ran at around 450-500W. The PSU just couldn't deliver that for longer periods of time, so occasionally the voltage dropped which is enough to lead to undetermined behaviour. I replaced it with a 600W PSU from a more renowned manufacturer, and although the name says 100W less, it was now reliably providing the 500W needed. Corsair is one of the better brands though, so it's probably just that 350W is cutting it too close.

If it's a good supply shop then they should give you a higher PSU to try out, to see whether it solves the problems, and to return if it doesn't.

25 dollars for a power supply? I would steer away from it faster than a kid would avoid a vaccine in the butt.

What does this Power Supply Calculator produce?

gregrocker said:

What does this Power Supply Calculator produce?

Comes up with 255 minimum, 305 recommended, and I put in 40% "capacitor aging."

Just a quick update.

Talked to the repair shop this morning, and the computer has been running without incident for 24 hours. When I brought it back yesterday, they plugged it in, logged it in, and it ran with no restarts all day. When they arrived this morning, the display was blank, but the computer had just gone to sleep. They woke it and it was still logged in, something that would not have been possible after a restart.

The power supply I got was a "Thermal Master" or "Cool Master" 350 watt supply, and I got it for only $25 because this place builds PCs, the PSUs come in cases they order, and it's been their experience that the supplies work fine. If a customer is building a PC for gaming, video, something stressful, they upgrade the PSU for the finished unit, and use the one that came in the case as a replacement, or to build a lower-end box.

The repair technician suggested I use a different power cord, which I'll do, and it the problem persists, either find a new outlet (probably not likely), or get a UPS to provide a "cleaner" stream of power to the PC.