Fresnel burning through gel


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so I have a 6" Altman Fresnel which is burning through gel like crazy. we're running a show now, and every 3 shows i need to change it. its twofered, and the other insturment never needs to be changed, but this one keeps burning through. always in the same place too. ive saved every peice, and the gel is in the exact same place, same size. i changed lamps, and that did nothing though. does anyone know what it may be?
What number gel is the fresnel burning through, and what gel does the other fixture have in it? Are both identical fixtures with identical lamps?
its R78

i have 8 other fixtures that have the exact lamp and gel, i havent had to replace one of them. the focus is also the same for the one twofered. theyre completely identical.
found your post on LN too.
If it's in the same place each time, and you're using different lamps, it sounds like a focal issue. Does this lamp have the same lense as the other? You said the focus was the same as the others. Try changing it. Mayyyybe a crack? Mayyyyybe a reflector issue?
I know it's twofered, but do you notice the lamp being any brighter than it's circuit buddy? Burning out more lamps than it should?
It really sounds like a focus issue, try changing it.
What kind of lamp are you using? I am assuming this is an Altman 6" die cast focus Fresnel

types for this model include:
BTL - 500W Q500 T6/CL/P ANSI BTL
BTM - 500W Q500 T6/CL/P ANSI BTM
BTN - 750W Q750 T7/CL/2P ANSI BTN
BTP - 750W Q750T7/4CL/2P ANSI BTP
BTR - 1000W Q1000T7/4CL/2P ANSI BTR
BTN - 750W Q750 T7/CL/2P ANSI BTN
We use the same one at school, I have never had any filter life problems with these fixtures. You might try warming up the fixtures before each rehearsal and show.
Question. This may end up being in a better post somewhere but how exactly does the lamp burn the gel away? What process is going on? I know the gel is plastic but every gel that I've seen that was burned out, the color was just removed from that section of the gel where it was hottest. What is going on there?

I assume we've tried putting slits in the gels...
I had this exact same issue when I did Sweeney Todd this summer. My two color downwash had at last 4 fresnels that did the exact same thing. We had to change the gel alsmost every day. Unfortuantely, the facility had no more fresenels so we had to just go with it. We concluded it was a bad lens and/or weird lamp adjustment.
Well the main polymer in gel is tinted with different substances to provide the color. These fade with heat much faster than the base polymer. You'll eventually see the gel melt and/or catch on fire.
Some random thoughts on the process of elimination technique for solving a problem.

First do what's simple to confirm or rule out a cause.

Is your lens clean? A dirty especially oil coated lens will retain heat which could adversely effect the gel. Try swapping lenses with a fixture known not to have a problem. If this does not solve it, have a look at your gel frame and swap it for another one. Swap the fixture in tact for another to see if it's the hanging position or the fixture.

All kinds of comparisons and observations in narrowing down the problem.

After this, research the differences no matter how minute between fixtures. Say a new reflector, different alignment of the reflector or position of the lamp and lamp base in relation to it. Check the cooling vents, look if there is any evidence of the fixture getting hotter than other instruments such as paint blistering. Make sure it really is a BTN. Take a voltage reading with a True RMS meter. Is the voltagle of this one the same as the other one you are comparing it to assuming the same control channel to both of them?

This amongst the above questions of lot number age and dirtyness of the gel, and look of it's beam of light intensity.

Local positioning. Is this one near or far away from a source of air flow?
Is it remotley possible that you have the reflector set up as a beam projector? Though not likley, you could be bunred by this . . . no pun intended.

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