HP Elitedesk 800 G6 mini - No power/no beeps

[mrrubik]

Hi all,

I have a very strange issue with a HP Elitedesk 800 G6 mini (35W) unit - I acquired it as a barebones unit (no CPU/RAM/SSD), when plugging in power without any of this, I receive the correct 3 long, 5 short beeps (CPU initialization error).

I acquired the correct CPU for this, an i5-10500T and 8GB of RAM, after installing it into the motherboard:

1. Plugging in power adapter does not trigger auto-initialize (quick fan spin/power on check), the AMBER LED below motherboard does blink to indicate power connected
2. Pressing power button does not turn unit on, the white Power LED will come on while the button is pressed, but turns off immediately upon release

I have tried the following:

1. CMOS battery pull, 5 mins followed by 30sec power button press with all power disconnected
2. Swapped CPU/RAM into another working G6 and confirmed it's working
3. Swapped CPU/RAM from working G6 into this unit, same symptoms

What is so strange is that the motherboard doesn't appear to be dead, as without CPU it will beep with power connected, yet after installing the CPU it appears to not work.

Any thoughts/ideas are greatly appreciated!