Altman 360Q burning thru gel

[zac850]

Hey guys,
I am designing a show up at a community theater near me, and they have a few Altman 360Q's, 4.5 x 6. One of these is a top-light position with G841 (a dark blue). During focus, in-between me turning the fixture on to 75% and walking to the fixture, there was a nice 1 to 2 cm hole burned in the center of the gel. It couldn't have taken more then 30 seconds to a minuet.

When I pulled the color, the unit looked that it was benched correctly. I put some R119 frost behind the gel, and the frost melted to the gel, but it hasn't burned thru yet.

Is this a problem with the fixture? It looks like most of the light runs thru a 2 cm circle at the center of the gel, so is it not uncommon for this to happen?

I do not have much experience with the Altman 360Q, using mostly only Source 4's.

It should be lamped with a 575 watt lamp (i haven't checked, and i'm not 100% sure about what lamp it is).

[Foxinabox10]

The lamp is the first place that I would look.

[wolf825]

I would say check the lamp for correct wattage is a good thing as well... A EHD 500watt or EHG 750-or some of the FLK 575's shoulld work fine. Depending on the base and reflector/lense depends on if it can take the FEL 1K I believe--Ship is the expert on the lamp choices and will probably chime in here to help further. However the problem primarily sounds like it is with the bench focus... Adjust the field to be a little flatter... It sounds like the focal point of the light is crossing and centering at the gel frame area.. On the back of the older fixture caps there are 3 recessed flat-head screws for adjusting the focus along with a long thin flat head screw in the very center, usually with a few nuts for locking, for locking lamp base allignment in and out of the reflector... On the newer speedcaps--the bench adjust is two big resin knobs similar to the S-4's on their caps--an inner and outer dial/ring and knob. I would suggest you make adjustments to the bench to fix this problem by flattening the field to reduce the hotspot in the center... Also--there is Heat Shield which is available...however it will do the same thing as the frost did... The only other suggestion I could make is to use a "Top-Hat" lense tube extendor and put the gel on the end of the top hat...

-w

[ship]

Wolf described it well enough for what I would also think. FEL lamps - bad Karma.

A top hat such as for a 6" Fresnel will have a gel frame slot in it thus if using a deep satuated gel and nothing else solves the problem - especially bench focus and going for perhaps a little softer focus and running the lens train to it's opposing position, I might use some heat shield in the same slot as the barn door, than my gel in the slot to the barn door.

Could also go with a little less saturated gel if planning to dim it. Anything 575w and under should not not melt thru that fast however. For 750w I might flood the focus a little more. This all after the bench focus is assured.

Could also be dirty lenses and gel. Could also change brands of gel though it's doubtful that one will be better than another.

[zac850]

This is new gel, fresh cut, so I doubt its the gel.

When I pulled the color and sharpened the focus, the beam looked near perfect with no obvious hot spots, so I think the bench focus is OK.

For what I use it for, the fixture is on for maybe 10 minutes total at a level of 30%.

It could be that the lenses are dirty. These fixtures are ancient and I don't think they have been cleaned in a long, long time.

I may be able to dig up a lens tube extender. I have a strange feeling I ran across some in a corner of the theater with what looks like, at a glance, a few 1K fresnels and some extra barn doors.

[Radman]

The bas for those fixtures do accept an FEL I believe, so check the lamp. Again, with that small a fixture thats that much closer the gel is to the lamp. This plus an FEL an I wouldn't be surprised with the results you described.

[propmonkey]

for dark gels i usually put a few tiny holes in the center or if its a larger gel like for a cyc i cut 2 little 1" vents in it.

[SteveB]

My gut feeling is the lamp is not an FEL. It was common to see FEL's in 6x22', 6x16's and 6x12's, more rarely in a 6x9, unusual in a 4.5 as it would also fry the lens, though anything's possible as the fixture will take an FEL (not rated though).

If there's no obvious hot spot in the beam, then it's simply an issue of wrong gel choice for the fixture.

One solution if you don't have a color frame extender (top hat with a gel frame slot on the end), would be to put in a top hat anyway and tape the gel to the top hat. Somewhat defeats the purpose of a 4.5 as the TH cuts the beam spread.

No great choices, I'm afraid.

SB

[jfbach]

Haha... Sad to say, but in my auditorium, it isn't uncommon to see FEL's in altman 360q's. That stops now though.

[moojoe]

jfbach, Ship wrote an post a while ago about the FEL lamp, good post, def. got me to stop using the lamp. may be worth the read

http://www.controlbooth.com/ftopic-1...rasc-stop.html