Hardware Insights Forum

Wester: I didn't test the rectifiers. The PSU just works fine after replacing them, so I think it's a pretty safe assumption that one of them was the culprit.

LongRunner: Possibly I figured that, While the heat may certainly reduce the current output, it's important to remember that those things are rated for 30A at 155°C. To have them fail that far below the combined 60A, the temperature would have to have exceeded the TJMax rating of 175°C. Even once we factor in the thermal resistance*, we would still end up at over 160°C at the casing. If things had really been getting that hot, there would have been far more damage to the plastic which was glued to them, as well as to the insulation washers than what I saw.

*The rated voltage drop at 30A load at high temperatures is 0.8V, so 0.8V x 20.15A Load (which each rectifier would have been under), which equates to 16.12W dissipated per rectifier. The rated thermal resistance is 0.9°C/W, which gives us a 14.508°C Delta, and 175 - 14.508 = 160.492

c_hegge wrote:To have them fail that far below the combined 60A, the temperature would have to have exceeded the TJMax rating of 175°C.

Given that most other manufacturers only rate their parts for 150°C junction, how exactly can ST's withstand more??? Maybe they're a bit optimistic about what their parts can tolerate.

The regulation, ripple, efficiency, and input filtering entries in the "Specifications and Conclusions" table for the Zumax are actually those from the Bliss, which have been accidentally left in.

And the Zumax's power factor is awful even for no PFC.

Fixed

Also in the Zumax, they took a shortcut with the earth connection, connecting the wire to the PCB instead of using an eyelet as required.

Wester547 wrote:There's another review of the CP-350 which was conducted on a 220V/50Hz line voltage with an intake temperature of 30-31*C and it couldn't even do 350W without fireworks (after a few minutes, no less, and it had worse power factor throughout the testing), yet despite using slightly different secondary rectifiers and a somewhat different bridge rectifier, but in every regard, looks completely comparable to the one you have, including the fan, but it looks like the one in the other review was spinning at full speed the whole time. I wonder how yours did better?

PowerLAB's unit was also much less efficient. I wonder why? That would explain why it blew up earlier.

I'd say it could be the fact that, if I recollect, c_hegge only tests each PSU for around 10 minutes per load - I wouldn't be surprised if PowerLabs upped that to an hour per load.