Does any one know why my PC, win 10 won 't start when pressing the on button, the only way is to...

[G+_Rich Mclean]

Does any one know why my PC, win 10 won't start when pressing the on button, the only way is to open the case and disconnect the 30 pin that goes from the power supply to the motherboard? Could it be the cable, the power supply or the motherboard?

Thanks

[G+_Damien Wessling]

Can you provide some more details Rich? Brand or component brands, when did it stop 'starting', does it power on again with the switch after re attaching the supply rail to the motherboard... etc.

[G+_David Wiggins]

It could be there switch itself. They wear out fairly regularly (esp the ones in a student computer lab I worked at once)

 

Also the switch connection to the mobo could have a short. Sometimes it's the little part that breaks.

[G+_Rich Mclean]

Is a self made computer, Gigabyte motherboard, once I re-attached the connector to the motherland it turns on.

[G+_David Peach]

If you look at a power supply pinout you can see which pin to ground to get the machine to turn on. In the link below you can see that you can short pin 16 to ground to make it power up. Ultimately that is where your switch is connected.

 

If you are able to reliably short 16 to ground (I'm saying 16 based on the link below, check with your supply to confirm), then the problem is probably the switch or connecting wire.

 

lifewire.com - Pinout for the Standard ATX 24 pin 12V Motherboard Power Connector

[G+_Rich Mclean]

Thank you all for your comments, I will follow your suggestions.

[G+_Akira Yamanita]

Some good advice in here so far. Here are my suggestions.

 

The TL;DR version:

 

1. Drain residual power and test.

2. Check the power switch.

3. Check for shorts.

4. Test with a different power supply.

5. Update motherboard firmware (and BMC firmware if applicable).

6. Check the CMOS battery.

 

1-5 are things that I've personally seen cause this issue and the order in which I'd test, although I would swap 4 and 5 depending on access to additional hardware and how awful the motherboard manufacturer's website is.

 

The needlessly verbose version:

 

It's most likely the power supply but it could be the motherboard too. Before doing anything else, check the obvious and confirm that it's not the power switch. You can easily confirm this by using the reset switch (if there is one on your case) as the power switch or using a jumper to briefly short the connectors.

 

Chances are that what's temporarily fixing the issue is the draining of the residual power (sometimes referred to as "flea power") on the motherboard. Unplug the power cable from the power supply and hit the power switch. This will drain the residual charge. Plug it back and it will probably boot normally. You can also just leave it unplugged for 15 seconds or so, but pressing the power button speeds up the process. It should appear to try to turn on when you do this. If it doesn't, then wait the 15 seconds (or longer). At least that will save you from having to unplug the motherboard connector. I have seen this as a one time issue but my guess in your case is that you'd have to do this every time.

 

Because power states are controlled by the motherboard, you can try updating the BIOS and BMC firmware (if applicable).

 

Although it isn't likely if it's an old build, I've also seen motherboard shorts cause very specific behavior like this as well. Check for misplaced standoffs and loose screws.

 

Googling around for this issue for things that I haven't seen took me to a post where someone said changing the CMOS battery fixed the issue. I haven't seen that myself, but it's something else to consider.

[G+_Golden Retriever]

Another madly difficult case I ran into was a metallic board stud in the case shorting against somthing it should not. The way to test is see if problem remains with board removed from case. If that turns out to be the problem you may need a plastic stud at one of the screw locations

[G+_Rich Mclean]

Can this CMOS, power supply or motherboard connector issues have anything to do (when it powers) for the computer to be very slow and sometimes apps not responding? Is this a sign that something is going to crash? We (my son & I) built it around 5 or 6 years ago. Thx

[G+_David Peach]

I would suspect hard drive. Check out SpinRite for a great tool on checking out your drives and getting them in shape or finding out if they need to be replaced soon.

grc.com - GRC | SpinRite 5.0 to 6.0