PWR loss or board defect?

[spark100]

Last night my dm800 lost the ch. signal so I tryed with other sat ch. nothing change then I did restart enigma2, same same, finaly I reboot it so it stop on first screen of the IP adress etc, after one mint its reboot itself and freez on the screen dreambox multimedia. finaly I removed the power cable for a while to cool it down but when I try to plug it again was dead, no led no screen display. I notice that some time when I plug and unplug the red led come and go once, more then that when its plug to pwr the ethernet leds are okay and I dont hear the fan but some noise like the CPU running or some thing else.
Please any idea how to confirm it dead?
Thanks