Tip: How to recognize a faulty power supply before buying it

TL/DR Tip: A good PSU is heavy, has many decent quality connectors and has numbers for specifications rather than super/ gaming/ ultra/ etc., and it doesn't come cheap.


Permalink summed up

1. Extremely high wattage claims at comparatively low prices are suspicious. There are simply no decent 750 W power supplies for $50.
2. If a PSU claims high performance on the 3.3 and 5 V rails while the 12 V rail numbers are low, then you know something is wrong.
3. The manufacturer does not specify any combined maximum performance, but instead only shows the maximum load for each rail separately.
4. Be careful with expressions like: Super, Extreme, Gaming, Combat, etc. 
5. Passive rather than active Power Factor Correction (PFC) leads to lower power efficiency.
6. Very few or short power connectors and cables might be an issue. A 750 W PSU usually has four PCIe connectors for graphics cards (2 x 6-pin and 2 x 6+2-pin), so think twice if a model only offers two (or at least consider your upgrade options).
7. The quality of the cable insulation may be poor, or the cables may not be insulated at all. 
8. Be careful if there are few or no indications of protection circuitry. If the PSU specification only says OPP (overload protection) or perhaps SCP (short circuit protection), this points towards a normal fuse. If the specification also says OVP (overvoltage protection), this probably means that it is equipped with a simple metal oxide variable resistor. These security measures by themselves are absolutely insufficient and cannot replace any kind of digital safety chip.