Dead TROTEC PAC2000S air conditioner
Safety note
The A/C is being powered by a ST VIPER12A switch mode supply. This type of supply is not mains-isolated, so all voltages (even the low voltages) are referenced to mains voltage.Don’t work on this device while plugged in without being aware of the implications of this!
Every metal piece, every wire, every component inside can be at deadly voltage potentials against mains earth!
Don’t connect any mains-referenced measurement equipment (like oscilloscopes), as they’ll create a short-circuit and damage things.
As Murphy’s law dictates, my portable A/C unit suddenly died while in operation on the hottest day of the summer.
No smoke, no explosion, just suddenly turned off and was then completely dead. No lights, no beeps, nothing.
Before the room got too hot, this needed to be solved. Let’s take panels off and take a closer look:
The power supply was was quickly identified as the culprit, because the logic board wasn’t being supplied with 12V.
I then checked all semiconductors on the power supply only to find that this schottky diode was a dead short in both directions. Oops!
After a quick diode swap, the PSU started up normally and everything was back in order:
(and yes, I’m aware of the issues with single hose A/C units…)