As a sound guy you'd think he should know about interference...
I once had a somewhat sub-standard light controler too, but that one had a properly attached cord with plug and strain relief, and it was only used far away from sound equipment (the sound equipment was plugged in on the ground floor of the school and I was sitting up on the 3rd floor with my box controling an 18W fluorescent bulb (in a rice paper ballon suspended above the yard to imitate the moon) and a string of Christmas lights.
The contraption was only used for one rehearsal since the performance didn't happen anyway due to bad weather... you neither want your audience to be rained on nor the performers be fried on a metal balcony together with indoor cords and equipment...
