I wonder why this wall wart lost its magic smoke

So halfway through doing my nails on Sunday evening, I had a rather inconvenient thing happen: the UV curing lamp, strictly necessary for curing my gel polish, just up and quit working. I pulled it apart to diagnose the issue and see if I could work around it to finish up my nails, and as it so happened the problem was an easy one to figure out: the wall wart had lost all its magic smoke.

Supplying 12v from my bench supply to the lamp restored its functionality. My nails were saved.

But that left a mystery: why would the wall wart just up and fail like that? Time for an investi-

Ok, I may not be a board-certified resistrologist, but I'm pretty sure these two 1.5Ω resistors didn't come from the factory with speed holes in them. I would also venture to guess that measuring 60kΩ is not quite within their tolerance spec.

But then the question is: why did these resistors lose all their magic smoke? They're the current sense resistors connected to the drain of the switching mosfet, so the first likely answer is that the mosfet failed short, but if it did then it must have since failed open, because it was reading an open circuit between the source and drain (as it should, given there was no voltage present on the gate).

It's possible that the switching controller hooped itself and wedged the mosfet on long enough to pooch the resistors before the charge pump drained. The controller showed no signs that it was attempting to twiddle the mosfet gate, so that's a distinct possibility.

I could possibly see if I could identify and source a replacement switching controller, along with some 1.5Ω resistors (unluckily not a value I have in stock, at least not in 1206 SMD), but that's a lot of effort to spend on a $5 wall wart.

Instead, I think it will live out its days in my junk drawer, possibly to one day surrender some of its parts for other projects, or possibly one day I'll fix it just for fun. Who knows what the future holds. Going back into service as a wall wart, however, is out of the cards given that I had to destroy the plastic case to get at the PCB inside.