Precision 490 - POWER ON issue

Hi

I have such problem with my workstation when in turn on the power - computer start POST with LED 4&3 (and also 1 for some seconds) and green power button but after that turn off and I cannot start it again.

I put movie here.

Also I made everything acc. to this post  but it cannot help.

Please give me any suggestion what it could be. PSU, motherboard...?

Thanks in adavce for help

BR

Robert