Z370 Aorus Gaming 7 won't POST after working well for 2 days

[Splosh]

I've just built a new PC that performed well for two days (no over-clocking). But today, not having changed anything, it refused to POST and the DRAM LED came on. The initial pattern was:

•   switch on
•   nothing for 3 seconds then
•   fans started, decorative LEDs and DRAM LED came on
•   thereafter, every 4 seconds fans and LEDs blinked momentarily

I then removed/disconnected the GPU, HDDs etc and now the pattern is slightly different and instead of the DRAM warning light I'm getting the CPU warning light as follows:

•   switch on
•    fans start, decorative LEDs light and CPU LED come on
•   4 seconds later everything switches off
•   4 seconds later fans re-start, decorative LEDs and CPU LED come on again
•   thereafter, every 4 seconds fans and LEDs blink momentarily

I guess the problem is most likely to be the PS or the mobo but if anyone has any thoughts on how a good system can die so quickly I'd appreciate them.
 
Main components
Z370 Aorus Gaming 7 Rev 1.0
Intel Core i7-8700K
Corsair Vengeance 32GB DDR4 3200MHz (2x16GB)
Asus GTX 1080
SanDisk Ultra II 480GB (for O/S and programs)
Corsair AX760 power supply
Corsair H100i cooler
Windows 10 (64-bit)

Other components
Two WD HDDs (for data, no RAID)
Orico card reader (with 20-pin plug)
Orico 5-port USB PCi card (with 20-pin socket)

[tboooe]

Your issue may be totally unrelated to mine but the symptoms sure sound similar.  I have the same RAM as well.  Do you have XMP profiles enabled?  If so try disabling.

[shadowsports]

Greetings,
Disconnect/remove all cards
Connect monitor to onboard connector
Leave CPU, Cooler and one stick of RAM installed
Disconnect 24 pin connector to MB
Leave MB battery installed
Perform a CLR_CMOS using jumper
Reconnect 24 pin MB connector
See if it will POST

[Splosh]

Your issue may be totally unrelated to mine but the symptoms sure sound similar.  I have the same RAM as well.  Do you have XMP profiles enabled?  If so try disabling.

Thanks for your reply.
I did enable XMP profiles whilst the PC was working ok but disabled again straight afterwards (assuming I saved on exit!).   

[Splosh]

Greetings,
Disconnect/remove all cards
Connect monitor to onboard connector
Leave CPU, Cooler and one stick of RAM installed
Disconnect 24 pin connector to MB
Leave MB battery installed
Perform a CLR_CMOS using jumper
Reconnect 24 pin MB connector
See if it will POST

Thank you Shadowsports.
I tried what you suggested and it made a difference but unfortunately not enough to POST. It now behaves thus:

•   switch on, a few LEDs flash momentarily and then go out
•   5 seconds later fans start, RAM LED comes on as does the DRAM LED
•   20 seconds later decorative LEDs come on as well
•   DRAM LED on for 3s then toggling to CPU LED momentarily, then back to DRAM LED
•   30s later there's a click; fans switch off, RAM, DRAM, CPU and debug code LEDs go out
•   3 seconds later everything back on again (then loop to previous line)

•   debug codes are (mostly) C1 or 4C - which don't seem to be defined in the manual.

[shadowsports]

Try with the other single stick of RAM installed in the slot farthest from the socket.
Perform the same CLR_CMOS procedure described above.
Attempt to POST again.

If that fails, disconnect all of the power supply connectors to the board..  EPS, everything.
Test the PSU by grounding pins 16 & 17




Turn switch on PSU off first, then use paper clip to ground
Now turn the switch back on.  If the fan on the PSU runs, its probably fine
If its support zero RPM fan mode, you'll have to test with an OHMs meter

If the PSU is working, its the CPU or the board.  My bet would be the board since the CPU worked for 2 days. 

Next, I would return or RMA the board. If the retailer where you purchased it from has the ability to test it, let them and you'll have confirmation. 

[Splosh]

Hi Shadowsports
Phew.
With one memory stick removed it now POSTs and boots properly. When replaced the problem recurs. Presumably that stick is broken so I'll RMA it.
That's magic - thank you for your advice, much appreciated.

[shadowsports]

Greetings,
Troubleshooting can be frustrating.  Sometimes its helpful to have another set of eyes on an issue.  All I did is help you rule out and isolate the problem.  Glad I could help.  Good work figuring it out.

Cheers