Are those in an aluminium box and with a shine perforated metal lid?
First thing I do with those (before first power up) is open them and check for bad solder joints and other obvious things.
Some solder balls are common and these may get loose and cause a short.
Also make the power transistors and diodes loose from the heatsink, make sure there are no burrs behind them and then mount them again with a bit of decent paste.
I once had such a power supply where some white stuff was smeared over the power transistors, but there was nothing between the transistor and the heatsink.
The next best thing would be a DC load and a thermal camera.
Then load it with some decent current and check which parts are getting hot, and how hot they get.
Also, do not assume those bricks are all the same. China is a big country, with over a billion people and there are many different factories that make very similarly looking stuff. The sizes of those power supplies is also standardized, which makes them look more alike. The build quality of these things also varies, and there are also significant differences in the way those things are built internally.