Altspot 1000 lamp failure

[jwl868]

When we went to use the Altspot 1000 today for the recital dress rehearsal, the fan worked, but not the lamp. Luckily, we had an extra lamp (and it was at least 10 years old, maybe older). Swapped out the bulb, and we were back in business.

Question 1 – What happened to the light bulb? (photo attached.)

Question 2 – Is the optics assembly assembled correctly: specifically, the back end of the reflector cone (?) is about 1 inch from the front of the lamp socket, such that about an inch of the lamp is behind the reflector. (See Photo.) I was wondering if this gap had anything to do with the lamp failure.

Now, this spotlight only gets used about once a year, and although I cleaned and lubricated it a few years ago, a lighting professional hasn’t looked at it for 15 to 20 years. As far as I know, the spacing between the reflector and lamp socket hasn’t been adjusted for 10- 15 years.


Thanks

Joe

 

[mrb]

that lamp looks like the envelope was contaminated, most likely from someone touching it.

 

[ship]

Lamp itself shows problems as to either being touched by fingers - oil or dirt from them or atmaspheric oil or dirt in the air on the glove which retained heat. Somewhere in that globe balooning up all around it that more seems like oil in the air than fingers, the glass got a micro crack in it and let the genie gas out of the lamp. No more gas.. filament went super nova in meltng down.

Not a big deal and common if not lamp hours failure for this type of use / lamp. What you do need to look at is the pins of this lamp in seeing if not the cause of failure perhaps also a problem if arched.

In the scene shop today and in shaving off 1/8" of material on some plywood I needed as a spacer for a drawer unit, I was offered the surface planer to do so. Took longer to do so and I wasn't impressed on the latter side of the board getting more hung up and less deep in cut plus maxing out at 5/8", but did the job until I needed another 1/16" from it and at that point I did the table saw which was a lot more simple to do. Anyway their surface planer lives under a tarp when not in use. I was getting to a point here afterall.

Perhaps if your follow spot isn't used much, a tarp over it would be a good idea so as to help keep lenses, reflectors and lamps clean for the most part for when it is used. Also, perhaps a denatured alcohol whipe down of the lamp before use would also be a good idea in these conditions. This amomngst other cleaning of the fixture concepts before use if in storage mode.

Less about the distance you note - optimizing the lamp to the refelector is a bench focus thing and should be done but less an issue here expected to be a problem if the fixture could in pre-show use get a good hard edge with out any dark spots in the center.

Yep.. worked on many of these fixtures over the years... I so far don't think it's a problem of optimization of the fixture over that of just a lamp problem so far. This especially for a halogen followspot. Some problems of CFM's have been found with replacement fans on arc source fixtures at times on the other hand - them espcially cracking lenses as a result.

 

[derekleffew]

Question#1: The picture illustrates the phenomenon colloquially called a "pregnant lamp." Caused by a weakening of the envelope due to heat, to the point of allowing the pressure of the expanding gases (halogens) inside to deform the glass. Edit: Upon closer inspection, it looks like the deformation begins exactly where the lamp penetrates the reflector, which is not unexpected that that location would be the hottest part of the envelope. When non-T/H lamps in radial ERSs would get pregnant, often they expanded so much that they wouldn't fit through the hole in the reflector, forcing one to disassemble the entire fixture. You likely didn't have that problem, as it looks like one relamps via the front of the reflector anyway.

Question#2: The relationship of filament to reflector appears to be correct. The foci of an ellipse are usually much closer to the ends than people realize, or is often illustrated. Without measuring the major and minor axes and doing the math,

Ellipse -- from Wolfram MathWorld
difficult to determine, and in the end, doesn't matter as the bench focus process will get the filament in the proper place.

I believe the Q1000 uses the same reflector as the 360Q, so if someone wanted to measure a reflector and run the numbers, that would be very cool. Do we have any HS mathematics teachers or math majors here?

The center of an FEL's filament is ~1 7/16" from the top of the base (flange). I'm guessing the filament center should be about 3/4" from the hole in the reflector.

Hey, you got 10+ years use from a 200-hour lamp. And you had a spare onhand when needed. Consider yourself blessed.

 

[JD]

Yea, on the Q1000 Altspots, the lamp sits pretty deep in the reflector, almost to the point where the filament windings start where it enters the reflector. The problem with the FEL (and it's brothers) is that the filament is pretty long. When centered, a lot goes to waste. This is why some of the newer spots with lower wattage lamps (but grouped filament structure) are brighter. (Think S4)

As for the blowout, This can sometimes be prompted by having an Altspot sitting around with the lamp on but the shutter doused. (Example; left on between shows.) As the output is blocked, the lamp/reflector area gets a bit hot.

I would simply check the airflow, make sure the reflector is clean, then chalk it up to "stuff happens."

 

[jwl868]

Thanks for the input. It's really appreciated.

Joe

 

[derekleffew]

... The problem with the FEL (and it's brothers) is that the filament is pretty long. When centered, a lot goes to waste. This is why some of the newer spots with lower wattage lamps (but grouped filament structure) are brighter. (Think S4) ...

To illustrate JD's point:

FEL/GLC
Both lamps have similar LCLs of 2.374/2.359", but the GLC's filament is more centered (closer to the theoretical point source source needed for the ellipsoidal reflector).
However, due to wattage, the FEL's filament has more material (tungsten) and thus will always offer more raw illumination. Whether or not a fixture with a GLx vs. a fixture with an FEL is brighter will always be a subject of much debate.