Friday, January 7, 2011

Quarter Shrinker Explodey Malfunction Postmortem

Last weekend there was a pretty epic Quarter Shrinker accident.

A few nights ago Rob, Chicken, and I looked at the Quarter Shrinker at length to understand as much as we could about what the mode of failure was.

The multimeter had wires connected to the positive bus, and also to the giga-ohm resistor as a voltage divider, so the multimeter wouldn't be subjected to the full voltage of the charging cap.

The problem is, the case of the capacitor is also connected to ground, so the multimeter was duct-taped directly to one big ground-plane.

We think there was a short somewhere inside the multimeter between the positive lead and the ground plane. This caused the multimeter to explode. In this explosion there was wire still had the alligator clip connected to the positive bus... as the multimeter blew apart, the other end of the wire swung around and connected (again) to the capacitor case. This caused a dead-short (with an unknown charge) across the former multimeter wire, which promptly vaporized.

Site of the former multimeter:

The vaporized copper blast where we think the dead short occurred:

Where the alligator clip was connected to the positive bus bar:

--Rest of the Set:--

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