Question about HP t620 powerup

[mrblister]

I just bought a used HP t620 thin client (not the plus model). I bought the correct power supply (from the hp specs): 19.5V, 3.3A, 65W.
The PS measures out at 19.5V.

The t620 has no msata connector soldered in, but it does have an unpopulated M.2 connector. There is no hard drive plugged in.
There is a VGA connector.

My first attempt to start the t620 had the VGA cable and the usb keyboard/mouse plugged in.
I expected the computer to start and enter the bios. (This is my first UEFI experience, by the way.)

When I press the power button and hold it, the hard drive light is white, not blinking, for about 5 seconds, then goes off.
So the t620 is not powering up.

I plugged a bootable USB thumbdrive drive, which may have been an MSDOS boot sector drive.
During one attempt to power up (and only one), the light on the USB thumbdrive did blink a bit before the white led went off.
Oddly, this only happened once.

HP said to reset the CMOS by pressing the CMOS button. No luck.

I don't want to pour bad money after good money, so here is my question:

Knowing that the computer "should" power up, and knowing that the computer is missing a SATA M.2 drive, could that be the cause of the problem
I'm having?
The HP literature says nothing about this. I would guess that UEFI would be available even if there are no drives plugged into the computer.

Thanks in advance!

 

[mrblister]

I can answer my own question. Between a power button light that was dim, and and the fact that I was using a KVM switch,
and the fact that the hp makes no sound, I did check to see if the kvm switch activated the second video output, but apparently
I missed that the video from the hp was in fact activated. I thought it was failing during power-on.

An hp manual said the white led meant there was an error, and that the computer was dead. Not true.
So my basic problem was unfamiliarity with my new computer.

The white led going dark after five seconds was because the hp was powering down after a 5 second press on the power button.

If there are no usb drives or M.2 drives in the t620 (i.e., no drives at all), the bios comes up after the hp logo, but goes directly into an attempt to boot over the network. This is confusing, because the usual trick of pressing escape does not bring up any menu -- just another attempt to network boot.

I plugged in a buildroot 64 bit usb bootable thumbdrive (which uses an msdos MBR), and the hp booted and ran.
When I powered up with this usb drive in place, presses of escape finally brought up the bios menu.

I also plugged in a 32 bit usb bootable thumbdrive, and it booted too.

Anyway, I made it this far.