Fractal Design Case
Gigabyte board
Corsair 650 watt PSU
Evga GTX 550ti video card
i7 sandy bridge, stock heat sink/fan

This is a hardware question, not Linux-related. (although this comp does have Linux on its primary HDD)

I built this computer about 2 years ago and have had 0 problems with it. About 1-2 months ago I turned it off and when I try to power on, it did nothing. I press button several times and nothing.

Check out ok:
PSU with tester OK, I dont know how to test the motherboard.
Checked all connections by completely disconnecting every cable/connector, blow out with air can, and reconnect carefully.
APC ups is running ok, checked all outlets with monitor and lamp, all ok
replaced PC power cable, ok

So after trying all these things, I was on my laptop and suddenly, the computer turns on by itself and boots to operating system normally. wtf? I logged in and everything runs normally. I shut the computer down and press power button to test and it powers on ok.... Weeks pass and I turn computer off again and the same exact thing happens, wont turn on at all until i give up and Im doing something else and out of the blue, it will turn on by itself again.

It will not turn off on it's own or anything, once its powered on, it runs like a champ. Also, there is no motherboard lights when trying to turn on. its just dead.....

Any ideas??

Okay, first off if your PSU is fine then it's not it.

However let's try this diagnosis:

1. Disconnect all RAM and devices from the computer and power it on. It should at least boot to the CMOS. Check and also see if Awake-on-Keypress or Wake-On-LAN is enabled. Disable them. In fact reset your CMOS with Load Optimal Defaults, and test boot. The system should at least power on and go to the CMOS with 0 RAM displayed. However be aware, some systems prevent this, so you may need to skip this and go to test 2.

If this fails, your motherboard or CPU is dying or is dead.

2. Connect the RAM, boot to CMOS, and run the Memory Diagnostic test. It should pass with all memory blocks available per stick tested.

If this fails you have a bad memory stick. Replace or remove the sticks as you test.

3. Connect the hard drive and optical media drive and boot to a OS with MemTest86+ and have it check the system. You should also have a SMART hard drive toolkit disk, and have it run it's diagnostics. It should pass with the drive having at least a fault tolerance write/read level of less than 5% disk space unusable. If it's higher than 5% your drive is toast.

4. Connect peripheral devices one at a time and boot to a Live DVD Media disk. Any Linux Disk will do as long as you can get to a desktop. You'll need at least some level of graphics. If after connecting any device the system starts to fault, it's either the PSU isn't strong enough to host the hardware, or the add-on peripheral device is dying or dead.

If you made it this far then it's probably an OS issue but I highly doubt it if you made it this far.

I had a similar sort of problem; pressing the power button and nothing happened, no fans, no lights, zilch! After trying PSUs, disconnecting disks, CDROMs, cutting memory to minimum I eventually decided to check the power switch. When I buzzed it with a meter it didn't seem to work. Stripping the front cover I found that I was pressing the "Button" which couldn't activate the switch behind as a pennyworth of plastic clip had broken and the switch itself had moved within the housing.

OK, so it's a long shot but as I said, it happens, I'd check the front cover button isn't intermittently operating the switch seemingly on its own. Then again you could have a dodgy switch?

My fix? I jammed a lump of neoprene foam between the switch and the housing to keep it in contact with the actuator button. Works a treat!

Play Bonny!

If when you press the button absolutely nothing happens (no fans, no power, no nothing) then it is probably the power button or PSU.

If you recorded previous PSU voltages when you bought the PSU, check them against the current ones, or check if the current ones are within normal range while running and are stable. Also check BIOS/UEFI settings to make sure the settings are not set improperly.

Also,. Reseating cables and connectors has always been annoyingly effective.

Hi,

Your system power button is normally open and connected to the Power Pins on the motherboard. You can use another momentary switch to test power on/off or remove the power pin connector from the pins then short out with a small screw driver or a jumper across the same power pins. I would be careful shorting the pins so you do not jump to the board. The MB does have a silkscreen protection layer but you should use caution. I always keep a spare push button switch in my tool kit with long leads to test that the system is sensing a press request to power on or off.

While you have the leads off you can use Ohm meter/DVM to test the switch for continuity when press and release of the front panel button.
Hope this helps.

Thank you all for the suggestions. I have not had a chance to try any of these as I've been working very late hours this week. I will try jumping those pins and testing the switch, hopefully this weekend.