So tonight we were getting ready for show when one of out crew went to focus a light that had slipped out of focus. When he touches the light, there's a flash and it goes out. After a brief scramble a replacement lamp is installed and it's plugged back in (the dimmers were on the whole time, just the fixture unplugged). All seems well up until we start doing a final channel check when that channel won't go off. We decide there's something up with the dimmer (as everything else checks out) and start doing some basic troubleshooting. We flip the pack off and the dimmer channel STAYS ON. Eventually we unplugged it and took out the fuse to kill that channel.
So-- my GUESS as to what happened is that the lamp failed into a dead short (bright flash) which somehow took out the triac before the fuse could go (and also eventually burned up the shorting bit within the lamp). What I can't figure out is how is it on when the master power switch to the pack is off??? We did open the pack up and didn't see anything obviously wrong (mostly to see if there was a big burned section and/or anything dangerously wrong).
Am I right? And any ideas why it's staying on even with the pack off?