Computer died... PSU?

[Pokestar21]

My computer just up and powered off while i was watching anime(tragic, i know). Windows did not shut down properly at all, just all the lights went off and it went quiet. I have ever experienced this kind of problem before, and I'm not sure what to do. Nothing seemed to be overheated, as everything was cool to the touch and my PC has great ventilation (custom built). All of the wiring was secure, and nothing seemed to be out of place. Attempting to start the computer again wields no result, no fans move at all. Looking around the internet, I'm leaning towards it being a PSU problem, but I cannot be sure, as I have no second psu to test. I really don't want to order another PSU with about being sure that it is the PSU. Is there something i can test? any signs?
PSU: Corsair CX-M series, CX650M 650W (i think it was 80 plus bronze, whatever that means) (semimodular)

 

[Tumeden]

There is a strange way you can test out the power supply, yes, but you need to completely unhook everything from your PSU and remove the PSU from your system.

After doing so, you can connect a small wire, or paperclip between the GREEN wire, and any of the black wires off of the 24 pin connector. This will act as if you were hitting the power switch on your PC (as long as its connected) and you would see/hear the fan running for the PSU. Definitely recommend to be super careful not to connect the wrong wires however. If it doesn't start at all, then your PSU is completely pooched.

 

[InvalidError]

There is a strange way you can test out the power supply, yes, but you need to completely unhook everything from your PSU and remove the PSU from your system.

The paperclip test does not tell you anything beyond whether or not the PSU is completely dead. If the PSU is unstable or outputting excessive noise as would be the case with dying/dead output caps (the most common failure mode), it may still turn on and power dumb loads like fans and lights "properly" yet fail to boot a system.

When the 5VSB supply dies, you often get no response whatsoever since the main switcher typically bootstraps from an auxiliary output on the 5VSB circuit.

 

[Pokestar21]

There is a strange way you can test out the power supply, yes, but you need to completely unhook everything from your PSU and remove the PSU from your system.

After doing so, you can connect a small wire, or paperclip between the GREEN wire, and any of the black wires off of the 24 pin connector. This will act as if you were hitting the power switch on your PC (as long as its connected) and you would see/hear the fan running for the PSU. Definitely recommend to be super careful not to connect the wrong wires however. If it doesn't start at all, then your PSU is completely pooched.

ok so i did that, and the fan was spinning, so the PSU isnt the problem, what might be the problem then?

 

[Pokestar21]

There is a strange way you can test out the power supply, yes, but you need to completely unhook everything from your PSU and remove the PSU from your system.

The paperclip test does not tell you anything beyond whether or not the PSU is completely dead. If the PSU is unstable or outputting excessive noise as would be the case with dying/dead output caps (the most common failure mode), it may still turn on and power dumb loads like fans and lights "properly" yet fail to boot a system.

When the 5VSB supply dies, you often get no response whatsoever since the main switcher typically bootstraps from an auxiliary output on the 5VSB circuit.

No noise whatsoever, during regular use, and the paper clip test. So is there no way I can tell whether or not the PSU is at fault or sort of dead?? I'm not super knowledgeable about that sort of thing.

 

[InvalidError]

No noise whatsoever, during regular use, and the paper clip test.

I meant electrical noise on the output rails, not audible noise. You need an oscilloscope to correctly measure that.

In my personal experience, when a PC or other device that used to work "perfectly fine" suddenly completely refuses to power up, it turns out to be dying/dead caps in the PSU around 90% of the time.

Since you get nothing from the paperclip test, that would strongly suggest a dead PSU.