Black screen, fans start to spin very fast after approx. 1 min., PC will not boot up

[I_am_Max]

My HP Z620 was working fine. I've been playing with BIOS settings in order to reduce the boot time. After restarting the PC it doesn't show anything (no signal) and after approx. one minute the fans start to spin with the maximum speed (very loud).

CD/DVD-ROM and HDD LEDs are blinking as normal after starting up.

what have i tried already:

* CMOS reset - the same behaviour.

* removed all HDDs and a second CPU voard - the same behaviour.

* tried to start workstation with a single RAM module - the same behaviour.

* replaced a video card - the same behaviour.

* removed ALL the RAM modules in order to test whether the mainboard would complain - it does complain (beeps,  power button is blinking in red).

I'm suspecting the thermal sensor, but I have no idea how I can check it.

Do you have any advice or idea?

Thank you!

[Brian1965 · Accepted solution]

Assuming all the on board connectors, memory modules and PCI cards are seated correctly, it does sound like a corrupted BIOS which can not be recovered by a simple CMOS reset. I would recommend you search for 'crisis recovery' in the forum and make sure you follow the instructions explicitly, timing is crucial to recovering the BIOS.

[I_am_Max]

Thank you @Brian1965, i was able to recover it using this great solution