New PC build - PSU has died 2x in 2 weeks

[adokitkat]

Hello,

I have built a new PC for my relative 3 weeks ago. I really hope I din't do anything wrong, because I build a few computers already & and nothing similar happened to me.
After I was done building (and yes, I have tried to follow all instructions from manufacturers), I did install all of the software such as Windows OS, MS Office, drivers, etc.
I also did dome light benchmarks and system seemed to work great & was stable.

 

My relative got his new PC for 4 days but something has happened - the PC wouldn't even turn on. 
So I went to look at it and it was dead PSU. Most of the time I pressed the power up button nothing happened, after unplugging and plugging back in it would just turn on for
a split second - fans and RGB turned on but then instantly turned off and stayed off again. I also tried the PSU directly with included pin tester and 3 days ago everything worked, now it was not turning on.
So we replaced the PSU with new one (exactly same brand and line) and everything looked ok, PC works again, I thought it was just a bad unit.

However, 9 days later, the replaced PSU is dead again.
I am wondering, if could there be something killing off PSUs in the build? Or is it just coincidence? 

(I don't know if this is important, but the relative insists on having plugged all of his PC stuff - PC, 2 monitors, printer, etc. - via 1 extension cord. Also I think his house doesn't have the newest wiring - it's kind of a hut.)

 

Full PC build:
PSU: Seasonic Prime Ultra 750 W Titanium (1 dead & replaced, still 1 dead)
Motherboard: MSI MAG X570 TOMAHAWK WIFI
RAM: Patriot Viper 4 Blackout Series 64GB KIT DDR4 3600 MHz CL18
CPU: AMD RYZEN 7 3700X
GPU: GIGABYTE GeForce RTX 2060 OC 6G
NVMe SSD: Samsung 970 EVO+ 1TB + some of his SATA HDD
Case: Fractal Design Focus G Black

Thanks for response.

[Jasonbas]

i dont know whats killing them its really wierd try getting more wats on the psu next time 

and no you didnt kill them or else they would not give you a replacement i have killed a seasonic psu and they didnt replase it

[adokitkat]

2 minutes ago, Jasonbas said:

i dont know whats killing them its really wierd try getting more wats on the psu next time 

and no you didnt kill them or else they would not give you a replacement i have killed a seasonic psu and they didnt replase it

I could return it within 14 days instantly though... Also this model has 12 years warranty. 

The weird thing is that they both work until they just shut down and stay dead.

[adokitkat]

I just read it could be some protection kicking in and PSU maybe then isn't really dead. After a few minutes unplugged it maybe would start to work again. But right now I have no access to PSU and cannot test if that's the case unfortunately.