This idea came up in another thread and I was thinking about posting it to pinwiki, but I wanted to get some more eyes on it to make sure there are no further gotchas that are going to pop up since I'm not planning to test it in a machine (I already drew it with the diode backwards once ).
The complaint was that the fuse doesn't blow when the transistors in the voltage regulator circuit short out and the voltage goes over 200VDC. This is actually a really common problem. The fuse doesn't blow because that's an overvoltage condition and fuses are overcurrent protection, but we can add overvoltage protection easily by adding a zener diode.