What is wrong with my PS4?

I bought a broken PS4. I bought it broken with full intentions of fixing it. I believe it’s the original model PS4.

The symptoms are:

I press the power button. It beeps. Nothing happens.

I wait a few seconds, press the button, it beeps, I hear a click, and lights up. The fan spins and hard drive revs up.

2 seconds later, the PS4 turns off. I hear a click when it shuts off from the back right side.

I have tried all the usual fixes:

Putting it on its side, using a different cable, gently hitting with the knee, changed out power supply, changed out harddrive.

All fixed did not work. Same issue no other symptoms.

Does anyone have a fix for this before I delve deeper and disassemble the motherboard? Is there anything I’m missing? Thanks in advance.