Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured.

In order to do that we increased current on the +12V2 rail until the power supply shut down. This happened when we tried to pull more than 20 A from it.

Manufacturers always leave a margin between what is written on the label (18 A in this case) and the level the OCP circuit is really configured (20 A in this case). We always like to see this margin as tight as possible, like happened with this power supply.

Then starting from test five we increased currents to the maximum we could with the power supply still running inside ATX specs. The results are below. After only a couple of minutes running under this configuration the power supply exploded, and we couldn’t finish collecting data. After disassembling the power supply we could see that the transistors from the active PFC circuit were the components that burned (see Figure 10).

Of course you are not suppose to pull more than the power supply labeled power from it, however we do that to see if some protection will kick in and prevent the unit from burning or exploding, which didn’t happen with this power supply.