[SOLVED] My first set up and first boot was fine for the first 30 seconds and then the screen went stripey. Red led light on mobo

[Brettw]

So i have built my son a pc consisting of a ryzen 3400g apu. A msi b450 gaming pro carbon a.c. Mobo. 2x8gb 2666mHz corsair vengeance ram. A 240gb ssd and a 1tb hdd. After building I switched on for the first time and all seemed fine
then 30 or 40 seconds later the screen went stripey. Have re seated the cpu. And both ram sticks. There is a red LED on the mobo which says cpu. but now I can't even get an image on the monitor apart Fron one that says "no signal". Any help would be fantastic. No bios updated or anything. No windows installed. This was at first switch on

 

[sizzling]

That motherboard may need a BIOS update to fully support a 3000 series cpu.

 

[Brettw]

That motherboard may need a BIOS update to fully support a 3000 series cpu.

Correct but now there is a light on the mono saying cpu. And there is no signal on my monitor now. Pfffft. Looking patience and my wife is giving me all kinds of search because of this. I think I give up

 

[sizzling]

Correct but now there is a light on the mono saying cpu. And there is no signal on my monitor now. Pfffft. Looking patience and my wife is giving me all kinds of search because of this. I think I give up

Does sound like the symptoms an incompatible BIOS can give.