Altman 902 and Altman 1000Q

[Capi]

My HS director e-mailed me a question today, since I am kind of his go-to guy on lighting issues. However, I am not familiar with either spot, so I thought I would put it up for the Board's opinion.

He recently acquired an Altman 902 spotlight from his church. He already owns Altman 1000Q's (2 I believe). However, he is disappointed in the light output in the 902. It is an old light, obviously, but it is in good condition according to him. He was wondering if it was possible or wise to replace the socket in the 902 to the same socket as in the 1000Q. Better lamp, better output. My gut reaction was, "No. That is a bad idea." But I really don't know. Thoughts?

I cannot really comment on the actual condition of any of the lights as I have not seen them personally.

 

[waynehoskins]

Yeah, the old 902 sucks. It's not worth the trouble to try to retrofit an axial reflector and quartz lamp into, in my opinion.

The high school I do stuff with had a 902 to start with (ten years ago when I was a student); we'd borrow the 1000Q from the junior high on shows when we needed two spots. The 1000Q was far brighter than the 902 at that throw, which was on the order of 75-100 feet. In college when I was LDing at the high school, we'd use the 1000Q and rent a 1K Midget; though they had the same specs on paper, the Midget was another useful step brighter than the 1000Q. In the years since, they bought a Comet, and it's on par with the Midget; a very useful step brighter than the 1000Q.

 

[Capi]

Hypothetically, how much work would be involved in "retrofitting" one? Is it actually possible/useful?

 

[derekleffew]

Hypothetically, how much work would be involved in "retrofitting" one? ...

For starters, gutting the entire interior of the fixture, and then installing new reflector, lamp burner, fan, and optic train. The 902 was designed around a spherical reflector and the Mogul Prefocus T-20 lamp (modern equivalent: DTJ). The newer 1000Q was designed to use an ellipsoidal reflector and FEL lamp. Oh, and reworking the sheet metal, as the 1000Q is physically longer.

...Is it actually possible/useful?

Possible? Anything is possible, if one wishes hard enough. [The magic of theatre / willing suspension of disbelieve / hard-headedness of old Technical Directors, etc.] Useful (practical)? No. You'd do better to build your own followspot from scratch, or use a SourceFour™-on-a-Stick (accessories).

 

[waynehoskins]

I suppose in theory anything is possible. In this case, at very minimum you'd have to swap out reflectors and ceramics, because the 902 used a burn-base-down incandescent lamp (DTJ, I think) with some sort of prefocus base, and a modern quartz lamp (FEL, GLC) is typically axially mounted. I suppose it's possible to mount it in another position, but either way it's some fancy dancing to get the filament center at the focal point of the reflector. And then there's the mechanical details of how that retrofit actually goes in there. Basically you'd be taking the back end of a 1000Q and putting it in the 902.

I wouldn't count on the retrofit to be of much use other than an experiment, though it would be an interesting experiment.

Hmm .. I wonder (and I don't know, this is just thinking out loud) if the DTJ and the BVT (or another mogul prefocus quartz lamp that's moderately available) have the same lamp center lengths. That, though not ideal, might let you upgrade to a quartz lamp in the existing reflector and ceramic. It may be worth a look at the datasheets.

 

[waynehoskins]

You beat me to it, Derek.

The 902 was designed around a spherical reflector and the Mogul Prefocus T-20 lamp (modern equivalent: DTJ).

I wondered about that as I was typing. I didn't remember there being a hole in the reflector in the old 902, but it's been nearly a decade since I touched that thing, and I've slept since then, though not enough.

And I was going to mention that the optical trains seemed to be substantially different, but then I forgot to do it.

Yeah, that all makes a retrofit be so not worth it.

 

[derekleffew]

...Hmm .. I wonder (and I don't know, this is just thinking out loud) if the DTJ and the BVT (or another mogul prefocus quartz lamp that's moderately available) have the same lamp center lengths. ...

Since I still have my GE catalog open, the DTJ has an LCL of 3 7/16". The BVT: 3 15/16". So no. Lowering a BurnBaseDown socket is (almost always) much more difficult than raising one.

 

[church]

I have a dynaspot which is a 902 with a fan and I have considered fitting a P28 base and trying a BTR lamp although I have not actually done it yet - as an experiment. I have the bits laid around so it is just spending the time to try - you would not want to have to buy parts to try this. You can swap the lamp for a BTR without changing the optics by fitting the P28 base at the correct hight - if you want to see the impact of improved lamp technology. After that it gets more interesting but can be a worthwhile learning exercise.

While the 1500W lamp produces lots of light it is not very efficient as a point source and the reflector and conza lens in the 902 are not very efficient at putting the light out of the front of the spot. The optics are in truth only about half a step removed from a fresnel. Think a fresnel with an iris and two more lenses attached to the colour frame runners and you pretty well have this followspot. Actually the fresnel would probably be better as it has a larger reflector and lens.

As Derek said a S4 with a HPL575/115V lamp makes a better followspot than the 902 and the 1000Q and my own experience is that it is marginally better than a comet. Use the HPL750W/115V lamp and it is not even a fair competition.

The other advantage of the S4 option is that if you don't need the followspot for a show you can always use the S4 as a conventional fixture.

BTW is the 902 you have correctly bench focused? I had trouble with mine because the focus lens was in the wrong position.

 

[Capi]

I have no idea if it is correctly bench focused. It is at my old High School, and I will not be back there for some time. If I ever get a chance, I will check it out. Thanks for all the help everybody.