Autopsy: Part 2
Disclaimer: Power supplies can have dangerous voltages inside them even after being unplugged, DO NOT OPEN POWER SUPPLIES. It’s just not a good idea. Opening a power supply and poking around inside could very well kill you. Don’t try this at home. Don’t try this at work. Just don’t do it.
One of two primary switching transistors (not, mind you, MOSFETs), rated at 15 amps and 400-500 volts.
On the secondary side, we have two of these for 12 V: 20 amps each, that’s decent, bit low for a claimed 36 amps, but not over rated at least.
5 V and 3.3 V each get one of these: 30 amps each there, that’s enough for the ratings.
The secondary side isn’t exactly chunky, but it’s not completely horrible.
Not a familiar brand to me. I doubt they’re very good. You can also see the shunts connecting the two 12 V “rails” together. At this point it’s worth noting that the protections IC supports OVP on all three rails and UVP on 5 V / 3.3 V. 12 V does not support UVP, nor is there OCP on anything. That’s… bad.
The soldering is pretty good on most of the unit, the wire connection points aren’t great. You can see where the foam that was under the PCB (with a plastic sheet under that) melted to the heatsink legs. Got a bit warm there.
On the PCB we have the name of the company that designed said PCB: Proper English is not what I was expecting to find here. Never heard of the company.
Lastly I went hunting for the fan control bits, and I found out why the fan never spun up. Here is the thermistor.
Just barely touching the 12 V / 5 V inductor. That thing never got warm, the fan never spun up, and the unit died. I suspect that this one thing may have been the difference between this PSU failing with a bang and this PSU turning in acceptable numbers and living. No proof of course, but this is kind of sad really.
Nowhere did I find any charred components (other than the fuse, anyway), but both primary switching transistors appear to be failed shorted, explaining the sudden fuse explosion. I expect they simply overheated due to no protections and the failed job of fan control.
Here we have a video of the last minute and a half of the Infinity 500w’s life. You can watch the fan LED dim out as the “12V” rail droops to ~9.2v, then BANG. If you just want the BANG, skip to 1:20 or so.
Watch the video
