Computer randomly shuts off while playing certain games

[brody854]

Up until recently, I haven't had any issues with my computer crashing or shutting down suddenly. But now when I play some games my computer will suddenly shut off--as if the power chord was pulled. Sometimes it's an hour into playing, sometimes 5 minutes. This has only happened with two games thus far, Shadow of Mordor and Overwatch (I've never had any issues like this with Overwatch in the past, but now I can't even click on a button on the main menu without it shutting off my pc).

What's strange to me is that I can run other games flawlessly without any issues, such as Grand Theft Auto 5 (which is certainly more demanding than both Shadow of Mordor and Overwatch).
I don't think it can be my computer overheating because both my GPU and CPU temps are fairly normal, and they remain the same with both Overwatch and Grand Theft Auto 5. I even underclocked my CPU back to stock to make sure that it wasn't being overworked.

My Specs:
GPU: GeForce GTX 970
CPU: Intel i5 2500k @ 3.30 GHz
RAM: 8 gb
Motherboard: ASUS P8Z68-V LX
Power supply: 700W
Operating sys: Windows 7

What I've tried so far:
-Underclocking my CPU back to stock
-Reinstalling Overwatch
-Scanning and repairing Overwatch files
-Updating drivers
-Uninstalling GeForce Experience
-Changing power settings from balanced to high performance
-Replacing thermal paste on CPU

As of now I can't even open a loot box without my computer shutting off.

Any help would be appreciated.

 

[Aeacus]

What's your PSU make and model (or part number)?

 

[brody854]

What's your PSU make and model (or part number)?

The model number says ATX-CB700W

Also some more info (why not):
AC Input voltage: 115/230V
AC Input frequency: 50-60Hz
AC Input current: 13A(RMS) for 115VAC Input
6.5A(RMS) for 230VAC Input

 

[Aeacus]

Replace your PSU ASAP since you have Apevia ATX-CB700W PSU in there which is terrible quality (Tier five) PSU.

Tier Five
Avoid IMMEDIATELY. These units are highly unsafe to use. No such protections added, very thin gauge wiring used, false advertising and too much to list. Reference to a higher tiered unit for a better, money saving and a much safer unit. For your safety's sake, please don't order or pick one up for use in your system. These units are a potential fire hazard and could even kill you, let alone your system.

PSU Tier list: http://www.tomshardware.co.uk/forum/id-2547993/psu-tier-list.html
Apevia PSU specs: http://www.apevia.com/ProductsInfo.asp?KEY=ATX-CB700W

Reason why you experience sudden shutdowns is because your crappy PSU fails to deliver enough power to your GPU once it's under the load. The longer you experience those PSU fails, the higher the chance PSU dies completely and most likely fries your entire PC as well.

For new PSU, look for good quality (Tier two) PSU, preferably great quality (Tier one) PSU if you can afford it.
Anything from Seasonic will do, for you, in 500W range. E.g S12II-520, M12II-520 EVO, S12G-550 or G-550,
pcpp: https://pcpartpicker.com/products/compare/TgW9TW,gYMFf7,fZyFf7,DPCwrH/
(All 4 listed Seasonic units are Tier two.)

All my 3 PCs: Skylake, Haswell and AMD are also powered by Seasonic, full specs in my sig. (Got PRIME 650 80+ Titanium in Skylake, M12II-850 EVO in Haswell and S12II-520 in AMD.)

 

[sizzling]

Agree, awful PSU. Not only is the quality poor its really a 550w and not 700w. It only claim 516w on the 12v rail which given the quality its unlikely it can get close to that.

 

[brody854]

Replace your PSU ASAP since you have Apevia ATX-CB700W PSU in there which is terrible quality (Tier five) PSU.

Tier Five
Avoid IMMEDIATELY. These units are highly unsafe to use. No such protections added, very thin gauge wiring used, false advertising and too much to list. Reference to a higher tiered unit for a better, money saving and a much safer unit. For your safety's sake, please don't order or pick one up for use in your system. These units are a potential fire hazard and could even kill you, let alone your system.

PSU Tier list: http://www.tomshardware.co.uk/forum/id-2547993/psu-tier-list.html
Apevia PSU specs: http://www.apevia.com/ProductsInfo.asp?KEY=ATX-CB700W

Reason why you experience sudden shutdowns is because your crappy PSU fails to deliver enough power to your GPU once it's under the load. The longer you experience those PSU fails, the higher the chance PSU dies completely and most likely fries your entire PC as well.

For new PSU, look for good quality (Tier two) PSU, preferably great quality (Tier one) PSU if you can afford it.
Anything from Seasonic will do, for you, in 500W range. E.g S12II-520, M12II-520 EVO, S12G-550 or G-550,
pcpp: https://pcpartpicker.com/products/compare/TgW9TW,gYMFf7,fZyFf7,DPCwrH/
(All 4 listed Seasonic units are Tier two.)

All my 3 PCs: Skylake, Haswell and AMD are also powered by Seasonic, full specs in my sig. (Got PRIME 650 80+ Titanium in Skylake, M12II-850 EVO in Haswell and S12II-520 in AMD.)

Thanks a lot, I appreciate the help. I'll invest in a new PSU and see if the problem is fixed.