Possible PSU problem? Computer doesn't always turn on.

Xeorth · Oct 8, 2014

Edit:

The post below is from one I posted a while back, but thought I would include in this as well, just in case anyone wants to know it greater to detail what my problem is.

If you don't want to read all of that, to cut it short for my computer to turn back on after it has been used, once the computer has shut down I then need to turn it off at the switch on the back of the computer. I have to leave it for a good few minutes (30+ mins), then for it to come on just flick the switch at the back and press the power button. If I don't do it in these steps my computer won't turn on.

I feel like it's a psu problem, but I'm not sure. Any help/advice would be really appreciated!

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Hey!

Just before Christmas last year I brought a bunch of computer parts from Amazon which would eventually be built into the computer I am currently using. I finished the build in January and after the first 3-4 months, everything was perfect and I was really proud of myself for building my first computer.
However, this was silenced when I would say around april-may time, my computer just wouldn't turn on when I pressed the power button. I looked around all my parts, making sure no wires had come out of place and then tried again - nothing. I left it for a bit, came back and tried again, this time it turned on. I thought 'Hey, that was a bit strange'.

Over the past few months this has been an on and off problem. You're probably thinking 'Why didn't you get this sorted out sooner.' and I have too, however I'm 17 and I'm currently in my most important and busiest couple of years in college. So I've honestly never really had the time to think about it.
However, over the past 2 weeks it has gotten worse. I can see that power is actually going to the computer since the lights on my gpu's are on, but nothing happens when I press the power button. It has gotten to the point now that I've noticed a trend. When I'm finished with the computer and turn it off, I have to actually have to flick the switch at the back of computer, so no power is going to the computer for it to then turn on later when I flick it back on at the back and press the power button. If I don't do that and I come back to the computer later and I just press the power button, I have to turn it off at the back and then wait for an hour or so, come back and then flick it back on, etc.

I'm going to be taking it to a repair/computer shop from them to take a look at it once I get some money together, but I was just wondering if anyone could give me a hand as to what the problem could be while I wait for that.

I'm sorry if this has been a very confusing explanation, but it's confusing for me as well as I feel it's a psu problem, but I'm really not sure.

I'll give my PC specs just in case it helps in anyway:

CPU: Intel Core i7 4770k
Moutherboard: MSI 787-G45-Gaming ATX
RAM: Kingston 16gb 2400MHZ
SSD: Hyperx 3k 240GB
HD: WD 2TB
GPU: 2x GTX 780
Cooling: H100i Watercooler
PSU: Seasonic Plat 860W

InvalidError · Oct 8, 2014

If you simply leave your computer off but the PSU still plugged in with the hard-switch on, you cannot get your PC to boot? In that case, my guess would be that the PSU or motherboard has issues on the 5VSB rail. If you have a multimeter, try measuring it by back-probing the motherboard connector after turning off your PC. If you read more than 5.25V, you likely have a PSU issue. You can also try seeing if you can catch a change in 5VSB value as you try turning your computer on.

In at least one of my old power supplies in my "to-be-repaired" pile because I do not currently own adequate test equipment to see exactly what their problem is and do not want to just throw parts at them on guesses, 5VSB can rise as high as 5.6V when the PSU is off and drops somewhere in the neighborhood of 4V as the PSU turns on. Unlike your case though, this behavior usually goes away once the PSU is warmed up.

Paperdoc · Oct 8, 2014

I'll vote for suspecting the PSU, too, based on my own very similar experience. In my case the PSU was in a machine about 6 years old. But the behaviour was almost the same as OP describes. At first it was the occasional incident where the computer would not respond to a push of the button on the front, but I could solve that by disconnecting the power cord at the back for at least 5 - 10 minutes. Then it became more frequent. I suspected an odd BIOS issue so I reset the BIOS and re-established all my custom settings, but that did not eliminate the trouble. I also found that I could "fix" it just with the power switch on the back, rather than unplugging. It got more frequent, and finally started shutting itself down in mid-use after about 30 minutes of use, then even shorter times. So, I finally removed the PSU and inspected its innards. I found a couple of large capacitors with bulged tops, so I replaced the PSU. Problem solved immediately.

Sounds pretty similar, eh? OP, if you could borrow a PSU and try it for a while, you might be able to prove that you can eliminate the problem that way, without spending money to do the test. Then you'd have a much stronger "case" to justify a warranty claim on the PSU. But right now, check the warranty period on that unit. You don't want to prove it is faulty too late, if you can avoid that.

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Possible PSU problem? Computer doesn't always turn on.

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