So I have assembled a x299 dark mobo on a custom water loop with the following parts:
 
i7 7820x
32 MB Corsair Vengeance Pro RGB 
evga x299 dark
2x aorus waterforce 1080ti sli on pci 1 & 4
optane 32mb
evo 850 m2 (carryover from an old system)
evo 860 ssd
2 WD 4TB HDD
waterblock is all EKWB
 
When i give power to the system - it runs through a few seconds of post - loops through some of the codes for 5 seconds then hits '62' for the 2nd or 3rd time before hitting 'C' then restarting. No power coming to the keyboard or mouse & no signal to the monitors. Any ideas?

I'm using the corsair AX1200i
 
System is on first assembly and has never posted successfully.
 
CMOS clear hit but no effect. BIOS version i have no idea - the system has never given me any life indicators to check that.
 
One LED is red - it is 3rd from the right - it's the only one that is red - I have uploaded a video of the code cycle to youtube:
 
 
 
 
 
 
 
 
 
 
 https://imgur.com/gallery/jlrPAKq
 
 
https://imgur.com/gallery/N9n8QRL
 
 
I hope these will help you with helping me!
 
edit Cool GTX fixed your links for you

turbomadman
My Dark did that on first start up. Make sure your settings in Bios is correct; make sure all your ssd nvme's are all recognized in nvme info, then set up which nvme will be the boot drive, very important. 
 
Edit: That red led is normal.

If it is boot cycling then he cannot get to bios

I doubt this would keep it from booting but once you do get it running you might want to run a cable to the lower 6 pin PCIe power connector just to ensure you are getting all the power your cards may need

EVGATech_GabrielT
Please see the FAQ link I have provided below, this will cover the the possible cause of the errors along with troubleshooting steps.
 
https://www.evga.com/support/faq/afmviewfaq.aspx?faqid=59687 

TY Gabriel - gives a good explanation as to the OP's "C" code. Lets hope that it is just a plug not fully seated and not either PCIe plug in the EPS slot or bent CPU pins

PSU is less than 2 years old. 
 
Installed the 6pin pcie in the below slot 6. All power block connections checked and seated securely. 
 
Tried both other bios switches - both have the same fail. 
 
I will probably check the cpu seating at this point, the install didn't give me any tough errors. 

I will attempt this on Monday when I come back to the workbench. I have the ability to grab a new PSU & check if its a power supply compatibility issue.

I checked the socket before installing and checked the CPU during the mount and didnt see any issues.

I really am hoping it is one of these simpler solutions. Mounting a new CPU isn't the worst but it's still a lot more work than PSU swap.

Those codes in the YouTube video looks like they are stopping at the Memory portion of the Bios post … b not 62. 
Maybe need to reseat the memory modules and verify the memory module slots are okay … nothing in them or bent out of place.
Also what is the memory module part number that you are using?
 
 

bcavnaugh
I have 3 EVGA 1300 G2 and 1 Corsair AX1200 that would NOT power on my X299 FTWK Motherboard. Never Tested them on my Dark MB.
 Yes I used the Cables that came with the Power Supply and did not mix them. The MB was in Bench Mode and not installed in a Case.
All 4 of the above Power Supplies are in use now on my X79 Motherboards without issues.
Interim I used an EVGA 1600 till I was able to get a EVGA SuperNOVA 1000 P2, 80+ PLATINUM 1000W 220-P2-1000-XR
 Power Supply.
Ref: https://forums.evga.com/FindPost/2792800 & View System
Also I did let EVGA know about the 1300 G2 not working.

Just for info I'm running my X299 Dark with a G2 1300 but it is the older one without the Eco fan switch.


 

Monday morning I'll pull the ram and test with some corsair 3000 and 3200 ram I have. Both are on verified & qctive waterloop systems now.

Cool GTX
OK -- maybe we are overthinking this:
 
Which USB ports are you using for KB & mouse ?
 
If USB 2.0 switch to USB 3.0 & visa versa
 
Do Not use the BIOS port
 
 
 

You made me have to double check the manual. I own an X299 Dark and had never heard of or seen any mention of a "BIOS Port"
 
I do not see anything in the manual referring to a dedicated port

OK, new thought ....
 
Confirm all points of contact between MB & case .... if it was not water cooled I'd say pull MB & place on cardboard

Thanks for fixing the link Cool GTX. 
 
If swapping memory did not help...
I seen the image of your system. That is alot of stuff connected to the mobo for first time start up. Possibly one of them may have gone bad. Maybe try disconnecting all data cables including power cables to those devices excluding the boot drive. Remove sli bridge. Disconnect bottom video card power connecters and disable that slot with the pci jumper. Remove any usb accessories, etc...Basically strip down your system to bare minimum to get the PC running. This will make diagnosing more streamline so you can hopefully pinpoint or narrow down the problem.
 
In regards to Cool GTX suggestion about possible ground out between mobo and case maybe you can at least use a flashlight to see if anything may have been caught or pinched and don't forget to try another usb port. 
 
Maybe try a different video card port.
 
Were all hoping to to see this through. Good luck.

bcavnaugh
A Metal Grounding Tab Stuck in the USB Port on the Back I/O Panel.

Good possibility.  We've seen that reported here in the Forums before...