Thanks for the kind words!
I won't say that what you have can't be improved upon, but I will say that to do so, you'll need to do more than
drop in a new light source. I experimented with a similar spot several years back, before
LED's were viable. I wanted to see what would happen if I used a deeper
ellipsoidal reflector and 575w lamp (basically just a huge version of an MR-16). I feel that my findings will translate to
LED as well. What I found was that the
conza lens did more harm than good, when faced with a more focused and even beam of light. These conza lenses seem to
play multiple roles. The "steps" direct the light forward (as parallel as possible) and if you'll notice, on the "bulls eye" of the
lens (nearest the lamp), there are very slight vertical ripples. I believe this is designed to replicate a
lenticular lens, spreading the light more horizontal, since the
filament structure of the original lamp is vertical and the light coming out of it will mimic that
pattern (in
lenticular lenses, vertical lines will spread light in the horizontal plane and vise versa). So basically, this
lens un-does all the good things a well-designed light source and
reflector combo achieves; spreading light needlessly in a
lenticular pattern since the lamp it's correcting for is no longer there. Removing that
lens cleared up the problem.
Assuming you do that, you'll also need to optimize the position of the
LED (and
reflector, if you were to use one) as the factory position would most likely no longer be applicable. What type of
LED system would you be looking in to? The off-the-shelf high-bay retrofit I mentioned would give a lot of light, but the entire source would need a
reflector. It's pretty huge, so what's already existing won't work - you'll lose a lot of light in the housing of the
fixture. Those retrofits also have
LED's placed on top, so you'll lose light there as well, since there's no way to capture it (assuming you go with a base-down configuration). Over all, any
LED "screw
base" lamp is probably not the right tool for the job.
COB
LED's would probably be your best bet, and won't need much of a
reflector (generally, I see them with nothing more than a shallow aluminum surround), but you will have to remove the
conza lens, optimize the position of the
LED, and make sure the
LED module can be cooled properly (anything bright enough will need significant cooling). Also keep in mind that the gels in the
boomerang may or may not
play nice with
LED's (thus, give funky colors and negatively impact the output), and that might require experimentation as well.
One other caveat is that the other plano-convex
lens in the
system is what we
call "coke
bottle green", in that it will have a greenish tint to the glass. This is primarily due to the fact that the best glass wasn't used for the optics. You will lose some of your efficiency in there as well.
So can it be done? Probably, but it will take some engineering, and even then, this light will fight you every step of the way. I would consider it a labor of love, and keep all your parts in case you need to go back (while you're at it,
mark all
lens,
shutter, and
socket positions on the rails). In terms of electrical efficiency, I wouldn't worry too much about a
followspot that is only used for a few hours a week. With the
platform provided, expect less light output, and a potentially short
LED life unless you really
tackle that cooling. Your beam might also be funky - just luck of the draw whether it works or not.
Now you also mentioned heat. I'm not sure if this particular
unit has a built-in fan, but if it doesn't, a little electrical and metalwork could get you one (or two). If it was my spot, I'd put one fan exhausting the air at the color
boom (mounted in the floor of the spot) and another just behind the
reflector (again, blowing air down and out of the
unit). You'd have to cut the proper-sized holes in the bottom of the spot, and use metal fan grilles to protect wandering fingers.
120v fans would be easy to
wire, just be sure to tie them together using a good 150-200°C rated fiberglass sleeved
wire (like SF-2), and heatshrink all connections. Use
terminal blocks for junctions as opposed to wire-nuts. You could sleeve the fan leads in fiberglass casing as well, for extra good measure.
One word of warning: This
fixture may have
asbestos wiring. If you see fuzzy white wires leading to the lamp
socket, that's what it is (not to be confused with woven fiberglass such as SF-2). This really should be abated anyway, but be especially careful when working around it. Remove it, bag it, and dispose of it in accordance with local codes.
I'll bet by now you're thinking of leaving it as-is.
