While loading the car for a shoot several weekends ago, I proceeded to drop my Nikon SB-600 from about 2 feet high onto the tile of my mudroom. I thought “crap, hope that survived”, and finished packing. I set up at the shoot, and my wife (who’s the actual photographer) started shooting, but complained the flash wasn’t working. Looking at it, the screen was misbehaving, it would flash inconsistently, and then after trying to power cycle it, it wouldn’t come back on. Uh oh. Shaking the flash, I heard rattling. Crap.
While the shoot was going on, I started looking online, and as it turns out, this is extremely common. It appears that the battery compartment rests on top of a large SMD inductor, that when the unit is dropped, with batteries installed, the impact crushes that inductor, which usually takes out the diode above it. See the ifixit article. Anyway, after the shoot (one flash down) a got the unit apart, and found that indeed, those two components were damaged. Also, while sifting through the rubble of the crushed inductor core, I found a 3 pin SOT-23 device. After looking, it came from the ZD301 spot. A zener diode. Huh. It’s marked 431, but it doesn’t appear to be a TI LM431. Some searching got me to a Russian site that indicated the unit was an RD43B-M, or a 43V zener! Apparently it’s some protection for signals coming in from the hot shoe (I think). No idea why it’s 43 volts, but…