Fix (not repair) of cheap switching power supplies

Four 36 Volt cheap Chinese switching power supplies.
Two 15 Amp models that worked properly under load, but the two 10 Amp models failed with all but the most minimum load.
I investigated and found a wrong part had been used, and there may be more yet to be found.

[@Wendy_Peng]

Hello, we are MATRIX established in 2003. We mainly sell DC power supplies, AC power supplies, LCR meters, electronic loads, power meters, and other equipment. We often have some defective machines or machines with damaged packaging. The recycling value is extremely high. Are you interested in buying faulty electronics?