no signal issue / changed everything except CPU

Jan 22, 2019

PC suddenly turned off and since then no signal, after checking inside CPU-Fan was not working, changed it, new one works, still no signal.

Tried another Monitor, another HDMI cable, tried another graphics card, unplugged graphics card and tried via motherboard VGA, no signal.

BIOS reset with taking out the battery, didnt help.

Then i tried another PSU, no signal, different RAM-Sticks on different slots, no signal

I have another PC and used the parts to check around, but its an Intel PC and this one is:

Amd fx 6300
Asus M5A78L-M LX3 Plus

Internet suggested me that its probably the motherboard broken, because its rarely the CPU.
the Asus M5A78L-M LX3 Plus is a shitty board with bad Vrams etc, ..

So i tried another motherboard, the Asus M5A97 LE R2.0

no signal

PC turns on, fans spinning, i can turn it off by holding OFF, monitor turns on and shows "no signal" and turns off.

i've checked this guide aswell:

i've already ordered a mobo-buzzer/speaker but i have aswell changed everything around except the CPU, anybody has an idea what i should do next?

thankful for any help