Pre-show checks all done, moving lights struck, checked and working, myself (the stage manager), my operator and my ASM were sitting peacefully in the auditorium discussing something or other when there was a godalmighty BANG from the rig above our heads. My operator said "that'll be a Mac lamp, I saw a flash from that 600". No worries, we thought, we have spare lamps, there's plenty of time. Operator got the ladder out and climbed up to the unit, opened it up, and extracted a lamp which was still in perfect working order. He put it back, climbed back down the ladder and went to the phone to call the hire company who own the unit to let them know that we needed a replacement, knowing that any repairs needed were not going to be possible in the time we had. At that point I went to speak to FOH to let them know that there might be a slight delay in starting the show, as we had to get the replacement unit to the theatre and up in the rig. I walked back into the auditorium to find a) a nasty burning smell and b) the operator walking towards the ladder carrying a fire extinguisher. He said "hold this, will you? Mr Sands is in the Mac but I might be able to put it out without an extinguisher." Up the ladder again, cover off the power supply - sure enough, there were small flames coming out of it! After an abortive attempt to blow the flames out, I handed the extinguisher up to him and the power supply was filled with dry powder....put the fire out, but what a mess it made...we roped the unit down to the ground and had a look, and it turned out the big capacitor in the power supply had let go in spectacular fashion, and the resulting spark had ignited some of the wiring insulation. The hire company got a replacement to us in double-quick time, we got it addressed and up, and managed to start the show on time - just very thankful it didn't happen mid-show. Chances are that if it had, the fire would have gone out by itself when it ran out of fuel, but the burning smell was not pleasant! The Mac (which was well under a year old) got sent to the New Zealand Martin dealers, who looked at it and sent it back to Martin in Denmark, and it turns out they're sending a new one back to replace it....It's not every day that someone says to you "Mr Sands is in the Mac" and it's something I don't particularly want to hear again!