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?