Question Psu problem or something else?

[HarrisEric]

So, while I was running my pc and literally just using YouTube my pc shuts off as if someone had flipped the switch on the psu itself, and then system doesn't turn back on anymore. Weeks prior I had same psu in a different system which had done the same thing as if someone flipped the switch, only thing that was different was it all powered on but GPU fan not spinning,so I kind of just said screw it and went back to my older pc, with same psu keep in mind and it ran perfectly fine until today, which is about 3 or 4 weeks after switching systems. So now today it happend and psu fans and everything else turns for about a second and stops I thought maybe the psu is dead,but to make sure I switched to an old prebuilt I had laying around and hooked up the psu to it,pressed the power button and it turns right on. This is where my confusion is. I'm not sure if it's the right place to put this topic and I am sorry (new here) if it is not, but I figured I'd give it a go. Psu is a 500w dynex. Systems I have used with it.
Core i5 4460
OEM Dell mobo
16gb ram
Nvidia geforce gtx 1050ti

PC number 2
Core i5 3470
Asus sabertooth p67 mobo
16gb ram
Same gpu

 

[Archaic59]

So, while I was running my pc and literally just using YouTube my pc shuts off as if someone had flipped the switch on the psu itself, and then system doesn't turn back on anymore. Weeks prior I had same psu in a different system which had done the same thing as if someone flipped the switch, only thing that was different was it all powered on but GPU fan not spinning,so I kind of just said screw it and went back to my older pc, with same psu keep in mind and it ran perfectly fine until today, which is about 3 or 4 weeks after switching systems. So now today it happend and psu fans and everything else turns for about a second and stops I thought maybe the psu is dead,but to make sure I switched to an old prebuilt I had laying around and hooked up the psu to it,pressed the power button and it turns right on. This is where my confusion is. I'm not sure if it's the right place to put this topic and I am sorry (new here) if it is not, but I figured I'd give it a go. Psu is a 500w dynex. Systems I have used with it.
Core i5 4460
OEM Dell mobo
16gb ram
Nvidia geforce gtx 1050ti

PC number 2
Core i5 3470
Asus sabertooth p67 mobo
16gb ram
Same gpu

Dynex are Best Buy house brand if I remember correctly and are total garbage. You need to replace that thing at the first opportunity with a quality brand/model.