Dell XPS 17 L702x: blank screen, no splash, no bios, no beeps, no boot

Hi everyone,

I have a Dell XPS 17 L702x that I was prepping to sell.  The basic specs are:

Intel i7-2760QM

16GB of RAM (4GB x4)

NVIDIA GeForce GT 555M with 1080p 3D screen

500GB 7200 RPM HDD x2

A19 BIOS

Windows 10 Pro

Like I said, I was prepping to sell the laptop.  The laptop was functioning properly.  I had wiped the HDDs clean and was in the middle of performing a clean install of Windows 10 pro from a USB drive.  I have done this before and never had a problem.  The install started correctly. I selected the drive that I wanted, and the installer wrote the files to the drive.  The laptop then restarted.  The power came back on, the fan started up, and I could hear the optical drive and HDDs spin up.  However, the screen stayed blank/black, and the Dell splash screen never appeared.  The activity light on the USB drive never comes on.  The normal functions keys do nothing.

Here are some troubleshooting things that I have tried:

I removed the RAM and HDDs.  I get the typical 2 beeps from not having any RAM.  Motherboard seem ok.

I have tested the RAM in my work Latitude E6430.  The E6430 will boot with the RAM from the L702x.  The RAM seems ok.

I have tested each stick of RAM one at a time in various slots in the L702x.  Same problem, blank screen, and no beeps.

I have connected the HDDs to the E6430 with a SATA to USB cable.  I can format and read/write from/to the HDDs.  The HDDs seem ok.

I removed the top cover and removed the button battery to reset the BIOS.  I held the power button down for an extended period of time.  Reassembled everything.  When I first power the laptop back on I get 5 beeps for removing the battery.  I get the same blank screen when I power it back up a second time.

I used Rufus to create a bootable DOS USB.  Holding down END and plugging in the power cable will cause the laptop to start up, but I'm still left with a blank screen.

At this point I have run out of ideas.  Please let me know if there is anything else that I can try.

Thank you in advance!