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Deformed 5K Bulbs

Published : 4th June 2004


Ladies and Gentleman,

Following up to the thread on exploding HMI and tungsten bulbs, I now have an interesting phenomenon. After bringing back equipment to a rental house (which I know very well, and that won’t trick me...) from an 8 day shoot, we noticed in 7 of our 8 5ks, that the bulb has blown bubbles. That means, the glass-ball had deformed in the upper half on the "mirror" side" side of the bubble. you can take a look at

http://mitglied.lycos.de/hintenlinks/deformed5k.jpg

This only happened to the 5k´s (7 out off 8!). the 10k's, 2k's, 1ks etc were all ok!). 5k's were all Arri-studio 5000, NOT dimmed, focused 3/4 - 1/1 flood, tilted NO MORE than 45 degrees downward. Bulbs were all Osram of different "breeds".

Electricity was house-power at proper voltage (230V/50 Hz) - only one problem with the electricity - in the neighbourhood was a welding machine, which caused the <500w and the Kinos to flicker when running for very short times - so short it did not show up on the 5ks.

Is anybody familiar with this kind of problem? since we did NOT check the bulbs on the tungsten units during check out, we can’t say that the problem is ours or from some other shoot, but 7 out of 8 5ks is pretty much for a problem I only had once in my electrical service life... anyone experienced something like that??

Best regards,

Daniel Pauselius
Electrician, Leipzig/Germany
www.kunstlichtkollektiv.de



Daniel wrote :

>"...we noticed in 7 of our 8 5ks, that the bulb has blown bubbles. That >means, that the glass-ball had deformed in the upper half on the >"mirror" side" side of the bubble."

One possibility is that Osram made a faulty batch of bulbs. This happens!!

In the US we send defective Osram bulbs, via our bulb seller, back to the company for testing and they are relatively straightforward about reporting their manufacturing failures.

If you want to spend the time you might try this in Germany.

Jerry Cotts
DP/LA



>this only happened to the 5k´s

Baby 5K's with 2 or more scims in them can often heat up tremendously when tilted down over 30 degrees. But most often the fresnel goes first.

Jim Sofranko
NY/DP



I looked at your pic - Given the situation as described - only tilted down 45 degrees (which is close enough to optimum for convection cooling) my first guess would be that the glass formulation for that bunch of globes is off - but it would be worth checking with Osram first on this because they will be honest when they look at them. It is often the case that an overheated globe will fail where it is cemented to the porcelain base...this is usually a sign that the lamp has been sitting in too high a heat.

Unless this particular run of Arri 5k;s was assembled with the reflectors too close to the socket (very unlikely unless someone used 2k reflector/socket combinations in 5k fresnels) I would have to point to the globes as being most suspect.

One other possibility would be if the globes had oil on them (from someone’s hand) or possibly dust, either of which would retain heat and possibly allow the glass to melt as it did...But I think this is not all that likely because chances are some of the globes would have failed from this and the deformation is so remarkably similar from one globe to the next.

If you find out what was the problem, PLEASE tell us what it turned out to be.

I once had 10 10k globes fail in a 1 hour period and it turned out that it was a bad batch of globes from the manufacturer - so I know that this sometimes happens.

Mark H, Weingartner
LA based



>Baby 5K's with 2 or more scims in them can often heat up tremendously >when tilted down over 30 degrees. But most often the fresnel goes first.

I think you are on to it Jim. Notice that you only had this problem with 5k's. Why not other fixtures? Perhaps you had the number on reason for blistering. Blisters in the glass of halogen are often described by manufacturers as being because of one thing; overheating.

In fact, the number one cause of a halogen bulb going out is over heating. In fact blistering and bulging are signs of normal bulb wear and life. And notice all of your blisters are in the same spot. I say you have an over heating situation with your fixtures, nothing more. If it was a manufacturing defect, you wouldn't have blistering happening exactly in the same places on 7 lamps.

Walter Graff
Producer, Director, Creative Director, Cinematographer
HellGate Pictures, Inc.
BlueSky, LLC
www.film-and-video.com



Daniel Pauselius writes :

>well, all bulbs were from different batches. We did send them to Osram >but on the phone, they said, the only possibility were such can happen >is when a tilting angle of 45 degrees is exceeded or the lamps get >heated up over the normal temperature

Why don't you perform an experiment and see if you can duplicate the problem.

If these were all good bulbs when you started, and you had such a high failure rate -- and only with the 5K's -- then it seems likely that it must be either the fixtures or the bulbs.

mein zwei pfennings,

Brian Heller
IA 600 DP



>One possibility is that Osram made a faulty batch of bulbs. This >happens!!

Well, all bulbs were from different batches. We did send them to Osram but on the phone, they said, the only possibility were such can happen is when a tilting angle of 45 degrees is exceeded or the lamps get heated up over the normal temperature (for example when neighbouring lamps heat up the housing or something like that). nothing of both was the case...?

Best regards,

Daniel Pauselius
Electrician, Leipzig/Germany



>Why don't you perform an experiment and see if you can duplicate the >problem. If these were all good bulbs when you started, and you had >such a high failure rate -- and only with the 5Ks -- then it seems likely >that it must be either the fixtures or the bulbs.

Take a look at the photo. Blistering doesn't occur exactly in the same place on seven bulbs for any other reason than heat. In this case the fixture and the way it as tilted and any number of conditions that caused overheating over time. Blistering of this type is caused by over heating, not bad manufacturing.

Walter Graff
Producer, Director, Creative Director, Cinematographer
HellGate Pictures, Inc.
BlueSky, LLC



Apologize for being late with any answers, but sometimes it just doesn’t work out...right know, we have _no solution_ for the deformed 5k problem...

( http://mitglied.lycos.de/hintenlinks/deformed5k.jpg )

All the lamps are hanging in a studio and behaving just fine, so we think the only possibility is, that someone on a previous shoot had a firm hand with some oily gloves and let the bulbs melt down OR collected all his bad bulbs and put them in our lamps (???ugh!! - one told me that this happens!) - only Jesus knows!

Thanks for all the suggestions

Best regards,

Daniel Pauselius
Electrician, Leipzig/Germany


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