[SOLVED] PC doesn't boot directly after shutdown. Fans spinning, no post

[Louis H]

Hi people, I've been trying to fix this all day and it is killing me.

When my PC is running it works just fine, but if I shut it down and then try to boot it up again it doesn't post. The disk drive beeps and the fans start spinning at max speed on my case, cpu, and gpu. The hard disk LED shows no activity (apart from one *tiny* flicker when the power button is pressed). I then have to hold down the power button for a few seconds to turn it off.

Some weird things I've noticed:
- On the first failed boot attempt the fans spin for a few seconds, stop spinning for one sec, and then start again, this time spinning indefinitely. On all further boot attempts the fan spinning is interrupted.
- When I try booting after reseating the CMOS battery, the fans will do this on and off thing three times before spinning continuously.
- On a couple of occasions I swapped the HDMI from my gpu to my mobo and the pc shut down.

I have:
- Replaced CMOS battery, and cleared CMOS settings by shorting pins. (multiple times at different stages)
- Removed everything but the mobo, cpu and psu, plugging HDMI into onboard graphics instead. Fans spun but no post.
- Used a different power supply (brand new CX450M) in this stripped down state. Still no post. Weirdly shutting down the PC with this psu didn't require me to hold down the power button.. only to press it.
- Added ram, no post. Added drives, no post. Added gpu, no post.
- Tried the new psu again will full components.
- Moved pc to a different socket. Same.
- Waited a while for a successful boot and looked at voltage levels on HWMonitor. Not sure if the numbers were good or not but they seemed steady.
- Flashed BIOS from v1.80 -> v1.90. No luck.

PC spec:
- Windows 10 Pro 10.0.17314
- i5 3470
- ASRock B75 Pro3-M
- Asus GTX 660
- Corsair CX430M
- G.Skill 2x4GB Ripjaws X
- Fractal Design Core 1000

If anyone's had similar problems or has any ideas whatsoever I would love to hear them! Running short on hope atm.

 

[scout_03]

use hwinfo and post the sensor page reading picture .

 

[Louis H]

Hey scout, here are the sensor screenshots https://ibb.co/fXgvCVz, and here's the system summary https://ibb.co/dJxg14D

Cheers!

 

[scout_03]

try tis unplug the dvd reader from system and psu and do the same for the case fan with only one stick of ram and try boot if it work redo the test with the other ram stick in the same slot on the board .

 

[Louis H]

Hey scout thanks for the idea.

I gave that a go - I unplugged the case fan from the mobo, and unplugged the optical drive from both the mobo and the psu.
I tried running it with one stick of ram in a few configurations, all of which failed; ram stick 1 in slot 1, ram stick 2 in slot 1, ram stick 1 in slot 2.

I did notice that the red HDD activity light does flicker for the shortest moment when I first power up the pc (with any ram configuration). It really is a short flicker and I'm not sure if it is significant.

 

[scout_03]

if flicker means it try to read from him could you try another sata cable from it to oard and even another slot on the motherboard to plug him .

 

[Louis H]

if flicker means it try to read from him could you try another sata cable from it to oard and even another slot on the motherboard to plug him .

Thanks for the suggestion scout! Sorry for the delay - the PC in question is my brother's, who lives at home. I went back to uni.

I tried a combination of different SATA ports on the mobo with both the old cable and two new cables. I tried both sata3 and sata6 ports. No luck unfortunately

However while fiddling around with these cables I discovered a really strange way to turn on the PC...

The PC was plugged in to power but the PSU switch was off. I pressed the power button on the case, only for nothing to happen as the PSU was off. Half a second later I flicked the switch on the PSU. The PC booted!

I can do this trick quite consistently, though the timing is finicky. Too long of a pause and it doesn't work.

Any ideas what is going on here? It seems to be that it needs a bit of a delay in order to actually boot. Maybe the cable connecting my case's power button is breaking?

Another thing I've noticed is that the PC cannot wake from sleep. The light blinks, the fans keep spinning, and kb presses do nothing.

 

[scout_03]

i would test system with another psu when power is on by thw dwitch nothing should flicker and if you press the start button on the case should start also ask your brother if he did switch psu off on the back the other test you could do is to test front panel power switch by unpluging the cable from case ans psu on power momentary touch the 2 pins on the board system should start and hdd light flicker until full system is on .