Hi folks,

I just want to let you know.
My almost 2 years old, outdoor mounted Smoggie PM 16000106 started to act up weeks ago. Sometimes it recorded ridiculously high PM values (sometimes 200µg/m³), despite being in an area with very clean air. A few days ago, the Smoggie failed altogether, it was no longer online on the map, nor pingable in my Wifi network.
So I removed it from its mount, together with its wall wart, and put it up in my lab.
There it worked for some hours, then failed again, same symptoms.
Long story short, it turned out to be the wall wart. On a USB tester, it read 5.16 volts with the Smoggie as a load, but voltage jumped around by 0.1 volts.
That had me thinking if its the wall wart causing all this. This wall wart (the original one I got with the Smoggie) has 2 screws top open under a sticker. Not this clip casings rubbish.
The PCB inside looked good.
But all 3 electrolytic caps were borderline or plain bad. The main filter (2,2µF 400V) read good on cap meter, but had 35 ohms ESR, which is way too much.
The worst one was the cap which smoothes the supply of the switcher circuit, it was completely gone (dried out).
No trace of leaked goo on the PCB to see, no bulged cap cans.
I replaced the caps and added a 10 ohms fusible resistor (which had a space on the PCB, but was not populated) to the mains input to reduce inrush spike currents.
Output voltage is now at 5.3 volts and much more stable.
The Smoggie PM now works again nicely for the third day straight.

BTW: Only work on these high voltage devices if you know what you’re doing.

Cheers,
Wolferl