Boot device led is red. Computer does not POST, unable to load BIOS

[Jimistooshort]

Self built computer. Specs as follows:
Asus X99-S ATX Motherboard (5x PCI Express 3.0, DDR4 Quad Channel, Socket 2011)
Intel i7-5820K Extreme Hex Core CPU Processor (3.30GHz, 15MB Cache, 140W, Socket 2011-V3, 28 Lanes PCI Express Generation 3)
Corsair CW-9060009-WW Hydro Series H100i 240 mm Extreme Performance All-in-One Liquid CPU Cooler
Corsair CX750 Builder Series CX 750W ATX/EPS 80 PLUS Bronze PSU
Corsair CMK64GX4M8A2400C14 Vengeance LPX 64 GB (8x 8 GB) DDR4 2400 MHz CL14 XMP 2.0
Asus Nvidia GeForce GTX 970 Strix Graphics Card (4GB, GDDR5, PCI Express 3.0)
Creative OEM PCI-E Sound Blaster Z Soundcard
Samsung 850 EVO 500 GB 2.5-Inch Solid State Drive
Seagate ST2000DX001 2TB Desktop 3.5 inch SSHD Internal Solid State Hybrid Drive

Has worked flawlessly for 2 years then it had to be moved in order to plug in an HDMI cable from a Slate Raven MTi. Devices were powered down with power supply switched off.

Tried to start computer and it gets as far as the initial BIOS splashscreen but will go no further - i.e. can't get it to load BIOS.

I've tried flashing the BIOS but that won't do anything.

I've checked all the connectors, reset the MB, the CMOS, MEMTest, including removing the BIOS battery. Nope. Boot Device LED on MB remains on red and I'm unable to get to BIOS.

I then stripped out all of the components one at a time including the HD's and RAM (had to put 1 chip back to pass MEMTest obviously) until all that remains connected is the PSU, MB, processor and one stick of RAM. Boot Device LED remains on red (VGA_LED is on red now too but that's because the graphics card is out and the X99 MB doesn't have onboard graphics built in).

I've ordered a new PSU in the hope that it's that simple but does anyone have any ideas? Something I'm missing? I'd rather avoid replacing components unnecessarily since they're so expensive. I had hoped to get at least 5 years out of this rig before anything needed revisiting.

Should the PSU idea fail is there any way to determine whether it is the MB or processor that's the issue?

[Menthol]

What if any Q codes does the board display?
Since you have it stripped down, take it out of the case and place it on a box or non conductive surface, remove the CPU and check for damaged socket pins, not likely, remount the cooler, don't over tighten the cooler, install one stick of Ram and your Video card, see if it will post to bios, try the ram in a different socket if it doesn't post

[Jimistooshort]

Menthol wrote:
What if any Q codes does the board display?

Thank you for the reply.

D9 = "Error loading boot option" according to the manual.

Since you have it stripped down, take it out of the case and place it on a box or non conductive surface, remove the CPU and check for damaged socket pins, not likely,

I'm trying to avoid disturbing the processor at this stage since I don't have any thermal paste or cleaner to reseat things. Obviously if it comes to it I'll have to. I can't see it being bent pins though. A new build perhaps but not on a system that's been running for 2 years. Literally only moved the computer 2 feet forward to allow access to the cables at the back - no opportunity for pins to get damaged.

install one stick of Ram and your Video card, see if it will post to bios, try the ram in a different socket if it doesn't post

I've tried all that.

[Menthol]

Was a shot in the dark, and really apply if using a large heavy Heatsink when moving a PC, you say you can run Memtest, don't you have to get past post to run memtest

[Jimistooshort]

Menthol wrote:
Was a shot in the dark, and really apply if using a large heavy Heatsink when moving a PC, you say you can run Memtest, don't you have to get past post to run memtest

Sorry, I should have been clearer - I ran the MEMTest on the MB which indicated the RAM was okay.

[Jimistooshort]

UPDATE

Well, it isn't the PSU nor is it the MB - I replaced them both.

Has to be the CPU.

Bummer.