Poweredge 1800 Issue, no image, amber light blinking

Hello,

I recently bought a used Dell PE1800 and I have an hardware issue that I can't really figure out.

Here the specs

Proc: Intel Xeon 3 GHz ( 800 MHz ) - L2 2 Mo (x2) 
Memory: 4GB DDR2 SDRAM 
Hdd: 2 x 73GB (10K TPM) SCSI U320 80 
Chipset: Intel E7520 

OS: I don't know since my problem doesn't allow me to check it.

The server can power on without issues, the HDD leds are on the green side, but absolutely no image and there's an amber light blinking on the front and on the back of the case but there's not "error" beeps. I've removed the PCI peripherals, reseated the ram but It hasn't changed anything

My problem is excactly the same as on this video: http://www.youtube.com/watch?v=mpIym37TeAo

Somebody already had a such problem of a poweredge server or do you have any advices ? 

Thanks a lot