How can I tell if my PSU is failing?

[NTMBK]

I have a 6 year old Corsair CX400 powering my system, and I'm not sure it's still working properly. My Frankenstein'd system has become a lot more power hungry than it was originally, with a 130W Phenom II CPU, HD7770 graphics card instead of integrated graphics, double the number of DIMMs, higher end motherboard, and so on. I've seen a lot of weird problems lately, which could be caused by memory, SSD problems, CPU problems, motherboard problems, or PSU problems, and I'd like to try and rule a few things out.

Is there an easy way of diagnosing my PSU (preferably without dismantling my machine) to see if it is still providing enough power at the correct voltages?

 

[Torn Mind]

You can get a PSU tester with an LCD screen. Although, some of them do not go into the hundreths.

A multimeter can also be used. Accurate ripple measurements need a true RMS meter, but for everything else, the voltage testing can be done without true RMS.