PC turns on when IT wants to

[mad1394]

Hey guys

Since around 2 months I have been having this weird issue. The pc will turn on ONLY when it wants to.
Once it powers on NO PROBLEM, gaming for hours is ok, no blue screens, no nothing. Normal pc is normal.
I have so far fought the problem my simply not turning it off but on a few occasions, like when im out of town for weeks, I have to. Lately it's been powering up harder and harder. It used to take 3-6 tries, well now it takes 30.
I am suspecting either the power supply or the motherboard, I am just not sure which is to blame. I'm sure I am going to have to take it to a repair shop since I can not buy parts blindly just to test, so the purpose of the thread is:
Has anyone else had a similar problem? What do you guys think?

PS: I have built a number of pcs over the years and I am semi experienced in dealing with hardware. When the problems started they did so out of the blue, the pc had had the same configuration for years.

 

[CAPSLOCKSTUCK]

It could be something as simple as the switch.
That is where i would start.

 

[mad1394]

Forgot to mention that the button on the motherboard is also unresponsive and when it finally turns on it is usually from the switch on the case.

 

[Tatty_Two]

I had a similar problem a few years ago, it got worse much like you have indicated, in the end and after lots of head scratching it turned out to be as simple as a bad contact on the PC's "on" button on the case.

 

[Caring1]

I had that issue with an old Dell desktop, some of the capacitors had started to swell and leak and it did exactly that, became increasingly worse.

 

[mad1394]

I had a similar problem a few years ago, it got worse much like you have indicated, in the end and after lots of head scratching it turned out to be as simple as a bad contact on the PC's "on" button on the case.

So what could I do to be certain ? Dissasemble the thing and try to start it by touching the wires "ghetto style" ? What did you do in the end? Was it a simple fix?

 

[rtwjunkie]

First thing I would do is inspect the board carefully, in light, including capacitors. You might try starting it ghetto style with a flathead screwdriver. If the motherboard is fine on inspection and it still doesn't start, I would start suspecting something in the motherboard or PSU if the below steps are unsuccessful.

Try stripping everything out, and starting with one RAM and cpu. Sure, if it starts you'll get a warning (no GPU), but at least you'll know it starts. If it doesn't, then it's likely motherboard or PSU. Then add one item at a time back, beginning with GPU and starting. If none of them are the offending piece of equipment, then it's back to motherboard or PSU, my money being on the motherboard.

 

[tr1]

You could also try shorting the green wire on the ATX connector of the psu with any of the grounds (black wire) - that should turn on the PSU (disconnect everything from the mobo)

 

[Caring1]

You could also try shorting the green wire on the ATX connector of the psu with any of the grounds (black wire) - that should turn on the PSU (disconnect everything from the mobo)

That only shows if power is coming from the PSU, not if it will work under load.
If you meant as a means of bypassing the power switch while the unit is powered up, good luck, it should work, but I doubt the switch is the issue.

 

[Tatty_Two]

So what could I do to be certain ? Dissasemble the thing and try to start it by touching the wires "ghetto style" ? What did you do in the end? Was it a simple fix?

In my case there was a small spring loaded contact that had slackened with use, I just bent it a bit and it seemed to work. if in your case starting the system from the motherboard is also problematic I would guess that it may be a board problem.

 

[tr1]

That only shows if power is coming from the PSU, not if it will work under load.

He did state that the PC is running fine once it starts up and showing no signs on instability

 

[Bill_Bright]

I agree to start with a visual inspection to make sure all your power connections are tight and secure. But then I recommend you swap out power supplies with a known good one. You must ensure you are supplying the rest of your components good, clean stable power BEFORE you suspect they are the problem.

 

[brandonwh64]

I had this same issue with my work PC when the PSU was on its way out. I changed the PSU and never had an issue.

 

[Bill_Bright]

Yeah, it sounds like a PSU problem to me.

 

[Sasqui]

If you're having a problem with both the case switch and the motherboard button, it's probably the PSU.

But... it's possible it's the motherboard, I believe there's more electronics between the on-off switch to the green/black wires on the PSU mainboard cable.

 

[Bill_Bright]

I believe there's more electronics between the on-off switch to the green/black wires on the PSU mainboard cable.

What??? Please elaborate.

Understand the front panel button switch is there to simply and momentarily short (connect) the two pins on the motherboard's front panel header. That signals the PSU to power on and is the same thing as doing the paper clip test that shorts two wires in the main power connector. And BTW, I do NOT recommend the paper clip test because there are too many tutorials out there with conflicting directions.

 

[mad1394]

It just came to me that I never tested the buttons on the motherboard with the pc in operation. See if it shuts down/restarts it.
Unfortunately this week I really need my pc to be operational but next week im planning a more agressive approach to the problem. Starting with a power supply switch.

 

[Sasqui]

What??? Please elaborate.

Understand the front panel button switch is there to simply and momentarily short (connect) the two pins on the motherboard's front panel header. That signals the PSU to power on and is the same thing as doing the paper clip test that shorts two wires in the main power connector. And BTW, I do NOT recommend the paper clip test because there are too many tutorials out there with conflicting directions.

I believe there is a relay in the motherboard.

 

[TheMailMan78]

Try disconnecting the Ethernet and give it a day. See if it boots by itself.

Edit: Never mind. I thought it was ghost booting.

 

[Bill_Bright]

I believe there is a relay in the motherboard.

Ah! I see what you are saying. Thanks for clarifying - but no, there is no relay in the motherboard's power on circuit. The front panel switch that connects to the pins on the motherboard's front panel header connect directly to the power-on pins in the PSUs main 24-pin connector.

In fact, there are no relays anywhere on the motherboard. Some very powerful (1500W) compact power supplies use a relay in the master power switch circuit because the current is too high for some small switches. But the DC voltages are too low in motherboards.

 

[TheMailMan78]

I would disconnect the main power switch from the mobo and boot directly from the board. This will narrow down the case.

Edit: Jesus never mind. I need to read all the posts in the future!

 

[t_ski]

This sounds like a similar issue I've seen with women. Have you tried talking to it nicely? Asking if it's lost weight or done something differently with its hair?

 

[Caring1]

He did state that the PC is running fine once it starts up and showing no signs on instability

Your point?
Why post a useless comment that isn't helpful if you knew his PC started up then?
My previous post still stands.

 

[Sasqui]

Ah! I see what you are saying. Thanks for clarifying - but no, there is no relay in the motherboard's power on circuit. The front panel switch that connects to the pins on the motherboard's front panel header connect directly to the power-on pins in the PSUs main 24-pin connector.

In fact, there are no relays anywhere on the motherboard. Some very powerful (1500W) compact power supplies use a relay in the master power switch circuit because the current is too high for some small switches. But the DC voltages are too low in motherboards.

I'm can't say for sure... one piece of evidence I've got was a fried motherboard of mine that wouldn't trigger the PSU to spin up (at all) when shorting the power pins.

Another is the fact that you can turn the power off via the OS, so there's got to be more than just a hard wire from the power header to the green/ground wires on the PSU. I.E. there's some sort of solid state controller/relay doing something in-between.

 

[Bill_Bright]

Another is the fact that you can turn the power off via the OS, so there's got to be more than just a hard wire from the power header to the green/ground wires on the PSU. I.E. there's some sort of solid state controller/relay doing something in-between.

Ah, I understand what you are saying and yes, you are correct. The chipset (via a command from the OS) can signal the PSU to power off too via a control signal.

A "relay" suggests to me some mechanical device (basically a remote switch) as found in some PSUs as I noted above, and that is what I focused on. Sorry if I cause confusion.