If a known good light doesn’t light in a circuit, that proves it’s not the light, so we go the other way; we start troubleshooting dimmers, circuits, patch panels and everything else in the feed. It’s possible that this could take a while, so if you have a show in the next few hours you might want to prioritize your tasks.
A good first place to start is with the dimmer rack. If everything appears to be normal with a sight inspection, i.e., LEDs lit, meaning power is on, no error messages such as overheating, and the DMX512 signal is good, then we might want to check the dimmer channel. “Swapping out” is still an effective troubleshooting technique here; it’s just a little more tedious and far easier to get confused. If we’re lucky enough to have a modular dimmer (some even have hot-swappable modules) then it’s a simple matter of swapping modules to see if the problem follows the module. If not, then we should look elsewhere. Perhaps the dimmer output is not connected properly. A good old-fashioned re-patch can prove you right or wrong pretty quickly. If the outputs are terminated with Socopex connectors, then perhaps we can just swap cables to see if another dimmer pack will work. Otherwise we’ll have to disconnect the circuit and use a continuity checker to see if we have continuity in the circuit. We can short the hot and the neutral (after they’ve been disconnected, of course!) and test for continuity on the other end. If that doesn’t isolate the problem, then we look elsewhere. Of course, we’ve already checked that every dimmer pack and DMX-driven unit have the correct DMX512 address, right? And let’s not forget the hundred-to-one shot – an unterminated DMX512 line.
– From John Kaluta’s Technopolis article in the upcoming June 2006 issue.
