ROG STRIX Z790-F no longer POSTs

[Merlingray]

Hi,

I have just done a new build on the STRIX z-790 Plattform (Intel i7 14700, G.SKILL Trident Z5 6800) running on Intel internal GPU. I got it to POST and installed Windows 10. I also switched on XMP in the Bios but other setting I left at default.

After switching off and restarting it no longer POSTs. On the Q-LEDs, CPU lights up and goes out, then VRAM lights up and goes out and then the board simply switches off (before it gets to VGA Q-LED and with no beeps and no more lights).

I have tried to install a graphics card, but this does not change the symptom.

I have tried to reseat the VRAM, no change.

AIO Pump seems to be running fine (so likely no heat shut down)

Anyone any ideas what could be causing this? If it was the XMP setting in bios, how can I reset this to default without getting into the bios?

Many thanks!

[JohnAb]

The easiest thing will be to clear the CMOS using the button on the motherboard itself. That will set everything back to defaults and hopefully you'll be able to get back into the BIOS for further troubleshooting. I assume the problem started after you enabled XMP?

[Merlingray]

Hi JohnAB,

Thanks for the proposal. I have just tried clearing the BIOS but still get to the same point (automatic shutdown). I have also tried taking out the VRAM. I then get warning beeps and then the shutdown. Running with one of the sticks of RAM also does nothing (no beeps and shutdown). Re. XMP I can't remember if it was the thing I changed last, but could be. 

[JohnAb]

Hmmm. OK. If a CMOS reset didn't help, the next thing to try will be to double check all cables for proper insertion at the motherboard and PSU. The big 25 pin connector can be tough to insert fully. If a lot of force is needed, support the motherboard from underneath while you do it. You've connected both PCIe power cables for the CPU? If that doesn't help, reseat the RAM (which I think you are describing as VRAM?). It should be in slots 2 & 4 if you have two sticks.

I don't know if you have a flashback port on your board, but have you updated the BIOS to the most recent version? Somebody recently had a board with an old BIOS as supplied that wasn't working with 14th Gen, but you did install Windows, so unlikely to be that.  

If nothing above works, try reseating the CPU and while it is out, check for bent socket contacts, dirt and dust in the socket and the back of the CPU. Before you apply paste and remount the cooler, make sure that the cooler posts (where they contact the motherboard) have not damaged any motherboard traces. When you tighten down the cooler, avoid too much pressure and make sure the tightness is even. The cooler needs to be snug, but not over-tight.   

If it booted once and you installed Windows, then I'm thinking that something isn't installed correctly. Is there any sign that it is trying to access the OS drive before it turns off? Doesn't sound like it gets that far. If you can get it to post, reset to BIOS defaults again for now.  

[Merlingray]

Thanks very much for all the suggestions! Next level diagnostic:

• Unplugged and replugged all the cables (ATX and 2xCPU)
• Flashed the Bios to the latest Version through Flashback (I assume it worked)
• Tried a different PSU
• Reseated and swapped around the RAM
• Took out the CPU and reseated it (I don't have an alternative Socket 1700 to try, but since it passed the CPU boot test and it did the same with a graphics card installed, I don't think it is a CPU issue) I also turned on without the heatsink and it got to the same point
• I also took out the SSD, so the board should not know about Windows or any installation (unless it somehow made a change to the BIOS)

So running out of options but to send the board back. Really can't think what else it is. Even if it was the XMP, the RAM is certified with it, so should run. Unless anyone has other suggestions.

[JohnAb]

I'm out of ideas then, sorry. Sound like something is wrong. My money is on the motherboard.

Best way is to try swapping out components, but very few of us have such options. CPUs can be faulty, but not common. Hope you get somewhere with it all soon. 

Before RMA, it might just be a good idea to try one RAM stick. If that works try the other and make sure they both work. If neither, then 90% the motherboard in my view. 

[Merlingray]

Thanks again @JohnAb . I'm coming to the same conclusion. Excalated it to Asus and will ask for a swap out unless they have further bright ideas. All the best and thanks for the help!

[JohnAb]

No problem, good luck with it. Nothing more frustrating than a PC that won't cooperate!

Just reset the BIOS to defaults and make sure XMP is off as one last ditch effort. I guess you've done that and re-flashing the BIOS should have set it to defaults anyway.  

You could also try powering off the PSU for a few minutes, That has helped fix some mysterious problems in the past.