Question No post and no USB power

[buckymorelike]

A friend's computer has been working for around a week now, then randomly shut off. After that he wasn't able to get it to turn back on afterwards.
When it's powered on, the case fans + CPU cooler spins up, but the GPU doesn't (I'm unfamiliar if his 5700 spins up automatically, and there's no LED's to see if it's actually functioning or not).
However, we can't get any USB power on both the case I/O and the motherboard I/O.
After clearing CMOS (both with removing the battery and shorting the CMOS pins), we noticed that the case power button flashed on for a brief second on bootup, but only after we cleared CMOS.
The Error LED's on the board flash "CPU" initially, then turn off, then it switches to "VGA", then keeps looping.
He's running :

• Ryzen 5 3600 (stock cooler)
• MSI B450 Tomahawk
• PowerColor Red Dragon 5700
• EVGA BQ 600w Bronze
• G.Skill Ripjaws V 3200 Mhz, 16 GB
• Kingston A400 240GB M.2 (for boot) and Western Digital 1 TB 3.5" Drive
• Windows 10 Home

So far, we've tried everything on the no post guide, then removing just the CPU, and then just the GPU to see the error readout. This went nowhere...
We flashed the BIOS to the latest using the EZ Flash utility (BIOS version 7C02v1D), but got nothing too.

Any advice here? Anything even similar to this just recommends clearing the CMOS, but not much else. At this point, we're not trying to get it to post as much as we are trying to diagnose this, so any and all thoughts are appreciated. (Posted to Systems because we still have no idea what's causing this.)

 

[Lutfij]

I would suggest that you source a donor PSU to try and power up the system while breadboarded. On a curious note, how did you flash the BIOS if you can't get the system to power up?

 

[buckymorelike]

I would suggest that you source a donor PSU to try and power up the system while breadboarded. On a curious note, how did you flash the BIOS if you can't get the system to power up?

The system powers up, it just doesn't necessarily post. We were still able to get error messages from the mobo, and etc. That board lets you flash from a USB drive (without a CPU needed). I'll see if we can get a donor PSU!

 

[buckymorelike]

The system powers up, it just doesn't necessarily post. We were still able to get error messages from the mobo, and etc. That board lets you flash from a USB drive (without a CPU needed). I'll see if we can get a donor PSU!

Update, we got a donor PSU and gave that a go. Same issue, no output. At this point, the only part we can't reasonably test is the motherboard.