Restarted computer, no display, mouse wont power on, everything else works

Warmanreaper

I been trying to fix my friends computer that we just built for him a few weeks ago, Ive made several posts on other sites, like Toms hardware & Reddit but they haven't really helped. The bold text is from the original Tomshardware thread I posted, just to give you all the context so far.   He has a Asus ROG STRIX B450-F, this Yellow light seems to be a problem.

So we just made a friend's computer not too long ago, using previous parts and buying some new ones, It worked for awhile, but last night he booted it up after getting off, and his Asus ROG Strix B450-F, puts on an yellow/orange type of light, he said all the fans etc work, but he has no display, and his mouse wont come on.

etc... after a few back and forth talking about ram, I troubleshooted some more on my own,

tried both sticks in both sets of slots and 1 at a time as well. Been trouble shooting ALL DAY. I made sure all the cords were plugged in, I tried 2 different graphic cards, I tested both A1&B1 A2&B2 and A2 both stick, B2 both sticks, but if I unplug the CPU power cord, the LED goes away.... so I'm guessing that means the cpu died? Can somebody clarify

 I also, tried what people talked about shorting CMOS, I didnt have the cap for it, so i had to touch it with a screwdriver for a bit. (?) I've also tried booting without a GPU, & ive tried booting with no ram regardless I still have the yellow light on, no errors or anything. The parts we installed BRAND NEW when it was assembled about 2 weeks ago, are the Ram, Powersupply, SSD, and I believe thats it. It's a bit sad because he just got a $1200 VR and after a restart, the computer kinda just died. 

CPU I Believe is a Ryzen 5 I havent looked into it too much I had to reapply thermal paste yesterday but I think its a Ryzen 5 2600 it's AM4 slot, Ram is 2 sticks of 8gb G.Skill Trident RGB, GPU currently in the system / was in it before it had LED, is a 2060, Ive also tried a 960 and a 970 inside it, PSU is some uhh.. maybe like 700W powersupply that we got from Microcenter, Storage, he has a 1TB HDD Baracuda I believe, and also a 500GB NVME SSD I don't know the specific brand of the SSD, or PSU.  the Yellow DRAM light is on.

TSTonyV

If the yellow light is one of the debug LEDs and it's labelled CPU, then yes, the board is detecting a problem that's CPU related when it boots. 

Whether it's actually the CPU or something else is a little difficult to say. If you had another CPU and another set of RAM to try we could narrow down the possibilities, but the CPU is the most likely culprit. Were the parts purchased from us?