New PC built yesterday stopped working

[ZFR77]

Hi,

Hi,

I build a new PC yesterday. Switched it on and it seemed to work fine.

Today I wanted to install the OS. I spent around half an hour browsing through BIOS options, but didn't change anything. The only thing I noticed was that it showed rpm of only 1 case fan out of 3. All 3 fans worked, but the other two fans were connected to the case fan headers and not to the motherboard. The third one was connected to header #4 and showed up in BIOS.

I opened the case, disconnected all 3 fans and and connected them to headers #1 #2 and #3 on the motherboard.

After plugging it in, it wouldn't start. Nothing happened. The diode on motherboard was off.

I plugged the fans as they were before. Still nothing.

Checked the power cord. It was working. I plugged and unplugged few power cables in case they came loose, but it didn't help. after some time of trying replugging some cables, and growing increasingly worried that I burned the motherboard by an ESD. I did 2 things after which when I plugged the power back on, the diode on motherboard went on:
_ I removed the side panel from the other side of the case
_ I unplugged the third fan from the motherboard header.
I did only those 2 things since the last time I tried, so I thought one of them did the trick.

After switching the power button, the motherboard worked, but...
_Only 2 fans connected to the case headers were working (obviously; the third one was unplugged), but the CPU fan, connected to a motherboard header didn't work either,
_ I couldn't switch it off using the power button. Had to unplug it.
The monitor wasn't connected

I plugged the third fan back on to a different header and the motherboard worked, but the fan wouldn't switch on, despite being plugged this time. Neither would the CPU fan. The other 2 fans worked connected to case headers worked fine.

After trying a few different combinations of fans connected to different headers, I'm back to square 1. The diode on motherboard is off, and it won't switch on, no matter whether fans are connected or not.

It's a Gigabyte GA Z97X motherboard. All parts are brand new. And as I said it worked fine yesterday during assembly, and today when I was browsing through BIOS.

Any idea on what could cause such behaviour? Any help on how to proceed? Thanks

 

[ZFR77]

Update:

I removed graphics card connected all 3 fans to case headers, and it booted perfectly.

reconnected 3 fans to mobo headers and it doesn't switch on again. Reconnected fans to case header, still won't work. Unplugged fans, still nothing.

Really weird. It was working just now. Any ideas on what the issue could be.

At least I'm happy the motherboard isn't fried.

 

[ZFR77]

Update 2:

For a moment I reached a stage where it would boot properly if lying on its side, but not if standing up.
Could it be a short somewhere? I looked around at all the wires and it seems fine. Any idea where to loo?

 

[inzgary]

You will want to be sure the cpu cooler is seated properly and the cpu fan is plugged in or the cpu will not power on. Also check if your power connectors are seated properly on the motherboard.

 

[voxgm]

Check your cables. Try a different PSU. Make sure no screws are loose or under your mobo and that all your standoffs are correctly placed. Take out ram or start with one stick and test. Unplug ssd/hdd and test. Try a different outlet or power cord. Start with some basics. Also check cpu temp in bios. Maybe over heating and waiting to cool off before booting.

Also you could try different fans. Makes sure the grounds/power connectors on the fans are correct and not backwards. Rare but possible

 

[ZFR77]

OK, after plugging and unplugging some cables, situation is stabilized. I'm now at the stage, where boot is ok if lying on side, but not if standing up. If I lift it horizontally while it's lying it goes off the moment it leaves the ground.
If I put it down and it's still off, tapping the case a few times puts it on again.

All fans tested and work properly on all headers. So it's a short or a loose cable somewhere. I'll continue the search.

It's a Corsair 760T case in case it helps.

 

[ZFR77]

It looks like the culprit was a loose 24 pin cable.

Seems to work fine. Problem is I'm still not 100% sure the cable is all the way in, but I've been working on pressing it for the past 30 minutes, and any longer I'm afraid I'll crack the motherboard.

Anyway, thanks all of you for your suggestions.

 

[voxgm]

Good to hear you found it. Check the pins on the 24 pin connecter and make sure all the little pins are pushed in. Sometimes those pins can Get push out of the plastic to much where the male pins on the mobo can't insert correctly