I've got a homebuilt desktop that is maybe 5+ years old now but has only ever had 1 hardware problem a few years back where I had to replace the PSU with a Corsair 450w.
The MB is a DFI Lanparty Sli-DR
Basically there was nothing wrong last night when I fully shut it down and went to bed.
When I got up I pushed the power button as normal but it was completely dead. I tried the normal, on-off switching, changing plugs, checking connections, unplugging the non vital stuff e.t.c.
I took the PSU out the case and jumpstarted it with a paper clip and it seemed to work fine, and powered some fans.
However when I use the 24pin motherboard connector everything is dead when I plug it in to the MB fully. BUT, there is a flicker (a light on the MB briefly lights and fans briefly start) as I start to push the connector in AND when I pull the connector out. One time I got the lcomputer completely on when it was half plugged in (but had to turn it off because I hadn't connected hard drives e.t.c.).
Nothing ever happens when it's fully plugged in but when the 12 pin connector is half hanging the system sometimes oscillates (light flicker and fans for 0.5s then 3s of nothing then flicker e.t.c. without me touching it)
It sounds like a mobo problem really I think? I'm surprised that something can be perfect before turning it off and then show no sign of life when asked to be turned on again. It's like with a light bulb, if you turn it on and it surges and breaks, sure that makes sense but if it just never turned on again it doesn't make sense to me
Which 12 pin connector are you talking about? what is it going to?
I had a similar problem; the computer would not boot with the power cable for the cpu plugged in. (would do the same flicker as yours if it was in) In my case it was a dead cpu. If you have another similar slot CPU lying around, or a friend has one, id start there.
If youve got a spare PSU or spare mobo id definately try swapping those out.
I suppose a power fluctuation over the night or something could have burned out a part.
Ah sorry I meant 24-pin connector in both cases
I don't think it's the case because I'm pressing power buttons on the motherboard as well.
That's interesting it might be the CPU but I thought that it would power on but not post if that was the case? It's worth taking out the cpu altogether and seeing if it will power on? Or will it do nothing with no cpu?
So I decided to take the mb out of the case to make it easy to try another CPU and check there are no shorts inside the case
I set it up on a wooden table and turned it on and after about 3-4s there was a bit of crackling and smoke from just below my chipset heatsink! I turned it off quickly
I thought I'd try it again before I went about buying a new motherboard and now it turns on fine with 2 different CPUs or no CPU but my motherboard stops at 4 lights everytime which is the step when it tries the CPU I think
I have a 4pin power connector that goes into a slot next to the 24pin slot but it doesn't seem to make a difference whether it is in or out.
I would have thought my motherboard is no good anymore after the smoking?