The case of the smoking bulb...

The case of the smoking bulb...  That's an LED bulb, a “candelabra” bulb enclosed in a glass envelope.  When I installed this particular bulb and turned it on for the first time, the glass envelope instantly filled with black smoke.  Interestingly, the LEDs were still working, though not much light escaped through the smoke.  I let it set for a few days to see if smoke would dissipate, but it did not.  So I took the bulb outside, broke the glass envelope (which allowed the smoke to dissipate), then brought it back in to take a peek under the microscope (photo at right) – where I see the proverbial smoking gun.  The yellow brick-shaped thingy is a single LED, magnified 60x.  There are dozens of these LEDs arrayed cylindrically to make up the entire bulb.  They're soldered to a cylindrically-shaped printed circuit board of some type, presumably made of a material that can take fairly high temperatures (these bulbs get quite hot in normal operation).  Those tiny little balls you see scattered about the surface are made of solder – highly conductive metal.  Normally on a soldered surface you wouldn't see very many of these; I think something must have gone awry in the soldering machine for this bulb.  I'd bet the problem was caused by some of these solder balls causing a short circuit.  When I plugged the lamp into a socket without the glass envelope on (dangerous, as high voltages are exposed), all but two of the LEDs worked fine.  The two dead ones were adjacent to each other, and the surface between them slightly blackened – that's probably where the short circuit happened.

Into the trash you go, dead bulb!  The vendor has already shipped me a replacement – when I emailed them about the black smoke, they offered to replace it immediately...