Asrock 870 extreme 3 - running but no video and no beep

Robert_459

Prominent
Jun 27, 2017
3
0
510
Hey guys.
i just assembled new/old pc. And i got no video on my screen with hdmi cable. (which is working)

cpu: phenom ii x3 720 BE (old)
mbo: asrock 870 extreme 3 (old)
gpu: r7 250x 1 gb (old)
ram: crucial 4b dd3 1600 (new)
psu: hexa 400w (new)
hdd: wd blue 1tb (new)

I've tried everything. cmos reset, battery out, plugged only cpu with mbo. but still no sound or video.

How can i be sure that mbo is dead?