Aurora R12, no display after cleaning inside

If the system worked fine before you opened it up and does not now, then something has changed. Either a cable is loose or not plugged in at all. Or possibly plugged in incorrectly. Go back and check each connection carefully including any cable or connection you may have inadvertently unplugged or loosened. Unplug and plug back in every connection just to double check your connections.

I have plugged the 4 motherboard cables, red, white, blue, and black into the power supply. Also, I have no Hard Drive, just the M.2, so the white cables were unplugged from the beginning. The GPU is properly connected to the power supply, It lights up properly.

Are you connecting to your display with HDMI?  If so, did you accidentally connect the HDMI cable to the board HDMI port instead of the GPU HDMI port?

The motherboard doesn't have an HDMI, just the GPU does. This is why I can't tell if the motherboard is not recognizing the GPU, in which case I won't be able to get video display to run windows or get into the bios. 

Does anyone knows why Dell doesn't offer any support on this cases? It was an expensive computer I'm only getting support from the community... 

So far, the motherboard has all the power connectors well placed. The GPU is well connected and it lights up so it does receive power correctly.

I read there are many situations where the bios has a failure and can't get any video and DELL sends a new motherboard as a warranty. How can I get in touch with Dell to ask for a replacement?

I have tested another PSU, and also a different GPU with no luck. So it has to be the motherboard, I guess the BIOS specifically, and since this board doesn't have any HDMI outputs I can't get any video at all. 

Re: How can I get in touch with Dell to ask for a replacement?

Use online Dell chat.

Re: Aurora r12

R12 mobo has got rid of the proprietary black 8 pin GPU_PWR socket previously seen on R9 or older Aurora (R8/7/6/5) mobo.  R11/10 does not have the black 8 pin socket either.  Good riddance.

White 8 pin eps on R12 is standard CPU_PWR socket.
an 8 pin EPS provides more cpu power to (up to 16 core R9 3950X) Ryzen in R10 and (up to 10 core 10900k) 10/11th Gen Intel CPU in R11/12.

to support cpu with more cores than previous one in R9, Dell engineers appropriately upgraded to the 8 pin cpu power socket.

In comparison, R9 cpu top cpu is 9900k, 8 core. R9 mobo had a 4 pin white CPU_PWR which is sufficient for the R9 cpu, 

and a separate Dell proprietary black 8 pin socket directly on top of the PCIex16 slot.  The latter one is gone on R10-12.  That socket is used to supplement power to gpu, not cpu.  Dell psu has a dedicated cable for this socket.  When using non-Dell psu, plug an 8 pin EPS to this socket.  An alien master said board would not POST without this gpu_pwr plugged in.

R9

It's a white one now, 8 pin EPS at the top of the board.

So there is some suspicious stuff here.

The GPU, as you can see, has eight pin slots, and that's all the power supply it can get. The power supply cable is the red one in the picture attached below.

I think I'm not missing anything here, so please let me know if something comes to your mind on the GPU power supply issue. It seems to me that this is all the power it can get, so it must not be a power supply issue on the GPU.

Additionally, I took a picture of the motherboard ATX CPU power socket, and it is actually an eight-pin socket, but it has only six cables attached to the socket to plug in. My CPU is an i7-11700KF. I have not modified any of the cables.

Thanks a lot for the quick responses

Thanks a lot!! It indeed matches everything you said, so I'm having the same connections. Do you know why the ATX CPU has only 6 of the 8 wires connected? Do you also have an 8 pin socket with only 6 cables on that CPU Power Supply socket?

The 8-pin that goes directly to the video card (red), should be a 6 + 2 type. You would need to slide the +2 onto the same 6 to make it an 8 pin.

They also can only go in 1 way because of the square-round-round-round on the connectors. You should never try to force them in. With enough force they can be made to fit, but the polarity of the +12 Volt would be wrong and that's not a good thing.

The other end of that red cable should be black and plug into 2 black slots right underneath the 4 x 6 colored ones that make up the 24 pin motherboard connector.

The white EPS should be red on the other end and plug into a red socket on the PSU, closest to the  24 pin connectors.

I am assuming you have the same PSU as mine, and whoever designed that PSU loved 6 pin connectors on the PSU so everything is 6 pin with lots of colors. No idea why they made it like that...

The PSU test button works well.

I don't know why the USB ports are not powering the keyboard or mouse, and I can't get any lights from the mouse or the block mayusc / block num lights on the keyboard. So I don't know if it's getting the M input from the keyboard. After turning on the PC and pressing the M and the power button simultaneously, the PC just turns off.

There is no diagnostic light on the Alienware head power button showing up. I recognize this lighting and don't see it at the moment.

Yes, I have the same 8 pin connector that is wired up as a 6 wire connector.

If you press the PSU test button on the power supply, the green LED should come on. Maybe test that.

You can also try M-BIST to see if anything comes up: M-BIST 

And there's also the diagnostic light (Alienware head power button): Diagnostic Light