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-Aaron

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We determined the cause was a quick and deep drop in the ambient temperature in the booth -- this was a drive-in in Texas. The booth closed for the night and the area was hit a unusually frigid cold spell overnight, down to near freezing and remained that way for the rest of the week. This theatre would close during the winter and because the winters were usually mild anyway, so there was no real room heating system, just a small area heater in one corner. So when the operator came in, the booth was really cold. The space heater wasn't much help.

We surmized that it was the sever temperature change that was the culprit -- starting the next night show after the equipment has been sitting in near freezing temps all day, then the dowser is opened and that rush of heat hits the lens barrel and elements -- bingo, cracked lens. By the time the second reel (change-over/6000ft reels) was ready to roll, the room and the lamphouse had already been on long enough to raise the temperature so that shock stress didn't happen to the other lens. We also noticed that the lens grip was tightened VERY tightly (those insecure projectionists needing to prove their manhood by tightening the lens lock so tight that you need a pipe wrench to loosen it -- you know who you are); this possibly putting extra stress on the lens via the barrel. When the heat hit it, the barrel expanded quickly and the lens cracked.

It is only a theory, but it was the best we could come up since the temperature change was the only odd element that was different -- everything had been running flawlessly for weeks before.

I hate to say this, but my real guess is (since you just opened) the tech left the dowser open too long while filing aperture plates. 5k watts is pretty hot. Water cooling only helps keep the projector head cool (which helps the film itself a little) but does nothing for the lens. Do you have glass heat filters installed(?), which will help. The pattern of cracks ("spiderweb") is an indication of what caused the damage; you could give the lens manufacturer a call (they may even still honor the warrantee.)

Was the crack on one of the outside elements? If you have turrets, check to see if it is possible to hit the lens when opening or closing the turret. On our Simplex projectors (with two-lens turrets and "swinging-hinged at the top" gates) if someone leaves the gate open and either opens or closes the turret -or- rotates the turret, it will hit the lens.

As a side note (and in my own opinion) there are not enough good techs to go around. A service company usually only has one or two good tech on staff, because there's not enough work to hire and keep more. Also, the sooner the building nears completion, the faster the work goes. If it is a larger place, especially a 16-plex or bigger, the sevice company must hire temporary help, sometimes "less than good" help, to keep up the pace.

At two of our theater installations (in a row) we had to do this, and at both of them we did have cracked lenses, which no one noticed until a few days after opening.

Since you say the place is pretty new, I'm going to bet that some raw recruit did something like that and fried the lens. With a 5 KW lamp, the lens will be damaged in pretty short order.

The only real solution is to replace the lens. In the mean time you can get your most important movie up and running by swapping lenses around. Look through your projector spec sheets and find one with the same size lens. (Focal length & diameter) Put the better lens in the house that has the best movie. If you can order the lens by overnight shipping or you can otherwise get a lens on short notice just put the house with the crummiest lens/movie out of commission for a day. Otherwise you are going to have to run a movie on that damaged lens.

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Do you use turrets or single lens? With turrets, about the only way the operators could have contributed to nicking the lens is on some projectors (eg Simplex PR-2000) the pad rollers and intermittent shoe can be in the lens' path when the turret rotates if they are open.

Steve

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