3k spot dimmer wheel problem

[Péo Durand]

Hello Y'all

I have three VL dim wheels that seemed to have burned a circle in the shading (see picture). We are a touring circus show in tent, I would think condensation then the heat of the lamp burned the shading, since we turn off the movers at night.

Has anyone experienced this in the past?

 

[JD]

Heat damage. General rule of thumb: If the light is going to be off for a while during a show, don't use the dimmer to douse it. Better to set up a cue that closes the douser but leaves everything else wide open. (Iris, Color, Dimmer, etc.) Often these things may still be exposed to the full output of the lamp even if nothing is coming out of the fixture.

The other case would be if the fixture is actually too powerful for the application, so it is left at a very low setting at all times. I noticed the burn does not look like it is at the black setting, more like 15 to 20% output. That can get tricky from a design point of view as the fixture may be briefly called to full output at some point during the show, thus requiring the fixture to be that powerful.

 

[Péo Durand]

When the the output goes to zero, the dousers shut themselves so no light output to the wheels. Even if the dim wheel is the furthest wheel away from the lamp, you think the heat could've burnt the wheel?

 

[coldnorth57]

that is true but the burnt mark on the wheel looks like it at 5 to 10% and sitting there for a long time might have burnt the wheel as John said above maybe a fixtur sizing problem

 

[soundman]

Call Vl. we had an issue with a batch of new in box lights from them in early 2012. the LD made a lowlight look for focusing with the lights at around 10%-15% and it burned holes in the wheels in a few hours. We were able to get the parts replaced under warranty. I wasn't on the lighting crew for that show so I can't be more helpful. I just got the statues updates from the techs venting about having to drop so many fixtures from the rig.

 

[JD]

Call Vl. we had an issue with a batch of new in box lights from them in early 2012. the LD made a lowlight look for focusing with the lights at around 10%-15% and it burned holes in the wheels in a few hours. We were able to get the parts replaced under warranty. I wasn't on the lighting crew for that show so I can't be more helpful. I just got the statues updates from the techs venting about having to drop so many fixtures from the rig.

It is defiantly worth making the call! The worst they could say is no. More likely, depending on the age of the units, they may send out replacements.
I would also look over the cue stack for cues that leave them at a dim setting.
Regarding the beam, there is very little drop-off in the beam level as it goes through the optics. Not exactly a laser by any means, but it is a tight focused beam of light and heat.

One other thought: If there are long unavoidable periods where the unit is dimmed to 15% (for example), you might want to put in some sub cues that vary them from 10 to 20%, (hopefully in some subtle way) so the wheel doesn't always sit in the same position. It may not solve the problem, but it would extend the wheel life. Of course, it has been mentioned that it may just be a defective batch that is prone to heat damage. (Again, back to the call!)