Hey all. I used to be active on here folding and sorting out questions until got annoyed with my EVGA products and deleted my profile. But now I have an issue maybe some of you smarter then me can narrow down or even pinpoint. Reconnected all my peripherals today to desktop I have on my work laptop during week. It wont power on. Blue LEDs on Ram have lights, some LEDs in top right corner of mobo and red LED near bios switch light up. When power on, other mobo LEDs come on for a split sec and all dies. When all dies, the few original mobo LEDs still lit. What i did so far and before I dismantle more, in order did it and between each step try to start up
 
Disco all external USB connections
Reset BIOS
Try alt BIOS
Remove CMOS and re insert
Remove all ram(which has their LEDs working)
Remove GPU
Remove all usb internal headers
Remove NVME drives
Left only mainboard power supply from PSU connected to Mobo
 
Same result, mobo lights come on for a split sec then dead except for a few mobo tiny LEDs. Theres no BIOS beeps or anything because it doesnt "power on". Yet there is some power for things like the Mobo and Ram Leds(when ram was connected. Maybe runs off CMOS battery)? But at this point all thats connected to Mobo are the LED lights for mobo accents and the CPU in the socket. Before I dismantle it the rest of way and get more irritated, should I be looking at PSU or is the Mobo shot or something else? Would need to add https:// to front because seems to strip out links but I cant upload any either so not sure how to share.
 
     photos.app.goo.gl/LF7qe2FHJ8dtemmv6
     photos.app.goo.gl/YcEg3zUjj6BXP25x8
 
 
 
Links above are a video of what does at power on attempt and an image of what is left connected inside by now.
 
Thanks,
Alex
 

Sajin
Time to see if it will work outside of the case. Hold old is the psu? Might want to try another.

Nope, when buy new sell the old. How justify kind of sort of buying recent stuff. Since dont game anymore the GPU gets to stay till toddler isnt a toddler :). Seems like best bet is to buy a rando new PSU(wouldnt matter amps or watts with nothing connected) to see if powers on to beep(for lack of everything else connected). If new PSU does same guess its the X299 thats died. At least I know the thermaltake supply has 10 year warranty. Too bad the fancy pants mobo i think only has 2-3 year and I know I'm over 2, not sure about 3. Looking for serial sticker to lookup, I'm guessing its on the backside of the 299 FTW, since all i see on front is a CIN #.
 
*your post was edited asking about old psu around. Thermaltake grand is same age as the mobo/cpu setup 2-3 id guess.

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Yet there is some power for things like the Mobo and Ram Leds(when ram was connected. Maybe runs off CMOS battery)? 
 
That cant be possible, because all the little LEDs turn off when i switch off the PSU physical power button. So some power must be getting to mobo from PSU?