SceneMaster Posted June 13, 2007 Share Posted June 13, 2007 The current show I am working on uses two pin spots to light a mirror ball. When I designed the show I intended to control the pin spots using the dimmers with a ballast load (usually a 1000watt PAR64). The pin spots are the 12v internal transformer type. I have often put pin spots on dimmers without any issue with a ballast load to ensure there is enough load on the dimmer for it to operate properly. However during the get in for this show one of the pin spots was accidentally were plugged directly into a dimmer with no ballast by one of the crew. Apparently the dimmer made an abnormal noise which I presume is related to the triac misfiring. The pin spot was quickly unplugged and thankfully the dimmer is fine, however the pin spot no longer works. I had a poke around the pin spot while it was hard powered with millimetre along with an electronic engineer who is on the crew and we can’t see any reason for it not to work or why an AC transformer would be killed by a dimmer. So my question is what actually happens to damage a pin spot\transformer when attached to a dimmer with no ballast? Edit: Pinspot in question was actually a 6v PAR36 not 12v. Link to comment Share on other sites More sharing options...
Trunker Posted June 13, 2007 Share Posted June 13, 2007 I have never had any problem with these. I have used one with a ballast load of a mirror ball motor and just pin spot (same one as yours) on its own and have never come across this. Interesting though. Anyone know anymore on this? Link to comment Share on other sites More sharing options...
musht Posted June 13, 2007 Share Posted June 13, 2007 is on the crew and we can’t see any reason for it not to work or why an AC transformer would be killed by a dimmer. So my question is what actually happens to damage a pin spot\transformer when attached to a dimmer with no ballast? Edit: Pinspot in question was actually a 6v PAR36 not 12v. Couple of things, D.C. offset caused by triac not switching symetrically as it passes through 0V, partly caused by inductive nature of load where the current and voltage are out of phase, means it acts like a rectifier for a millisecond or 2, only a milisec or 2 but its happening 100 times a second,transformers don`t like DC at all it overheats them and cooks windings. Voltage overshoot is other explanation have heard , where inductive load can act like a car ignition coil, cut the power as triac dimmer does, magnetic field collapses and energy appear as big voltage spike, can be enough to flash over insulation in trafo windings.One reason why Reverse Phase Dimmers are rare, inductive loads kill them stone dead. LSC has a white paper on inductive loads and dimmers on their website somewhere. Perhaps someone else can pick up any fallacies might be propogating in my explanantion Link to comment Share on other sites More sharing options...
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