LAUGHTON ELECTRONICS |
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A Special-Effects Repair: usually I try to fix stuff so it DOESN'T smoke |
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This story concerns a repair job typical of many I've undertaken. I had no training or prior experience with the equipment, and worked without schematics and service literature. |
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We've
all seen smoke used as a special effect, either in the movies or
perhaps at a nightclub or discotheque. But the machine that produces
the smoke is a comparative mystery. How does it work? And if you own
one that has stopped
working, who ya gonna call? The machine I serviced was a Rosco 1500 that came from The Blyth Festival. The Tech Director there knew me well enough to expect that, even if I'd never seen one of the devices before, I'd be able to figure it out — and of course she was right. The principle is simple enough: a small electric motor drives a pump that delivers a dribble of fluid into a heated metal chamber, and the composition of the fluid is such that heat causes it to boil into clouds of harmless smoke. This particular unit featured an electronic heater thermostat and a variable power supply for the pump motor so the rate of smoke production could be adjusted. The whole thing was roughly the shape of a shoebox, and it included jacks that could connect to a remote control. With the cover removed it was easy to see that the fault lay in the power supply. The power transformer was obviously blown; its windings were visibly blackened. (It occurs to me that they probably produced some smoke of their own!) I selected an appropriate generic replacement transformer, installed it and and new fuse, ran some extended tests and returned the unit to Blyth. The two photos on the left show similar machines. In the upper photo you can see the little access door toward the back; the lower photo shows the door flipped open, revealing instructions and the controls inside. Bundled at the top are the Remote Control and its cable. |
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