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This topic comprises 2 pages: 1 2
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Author
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Topic: Spots developing on Osram bulbs
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Mark J. Marshall
Film God
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Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002
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posted 03-14-2003 08:10 PM
We're noticing a phenomenon here, and we're not sure what's causing it. We're running the Osram XBO HOFR 2K and 3K bulbs, and we're noticing small spots developing on the envelope, usually near the back end (the cathode?). We've called around to several other theaters in the area, and they're noticing it on some of their bulbs too. I'm not sure about the other theaters off hand, but we're using Strong consoles.
At first we were thinking someone was touching them when they put them in, but that appears to not be the case. I did a forum search and found that we should order the "Technology & Applications" book from Osram. In the mean time, does anyone have anythin they can offer off the top of their head that may clue us in to what the problem is? Also, has anyone else noticed any spotting on Osram bulbs recently?
Thanks!
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Rick Long
Jedi Master Film Handler
Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999
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posted 03-16-2003 11:14 PM
The reason that I asked about the type of Strong console being used, has to do with our experience at a couple of theatres using used equipment.
The older Highlight models brought air in through a relatively small fan at the back of the lamp and used it to cool the ends of the lamp. Mind you, these lamps were designed for a 3K maximum not for the higher watage bulbs that we were forced to put in them.
The Highlight II, on the other hand, uses a large fan forcing plenty of booth air into the "dog-house" behind the reflector. This has two advantages; the reflector is cooled by the heat-sinking effect of the pressurized air (pointed out by John Pytlak in another post) and the air rushing through the hole in the reflector around the bulb.
This air with a horizontal forward vector, meets the heat being reflected from the perpindicular heat filter. Fans, mounted at the front of the lamp and blowing up, just in front of the bulb, combine to send this hot air up the stack (which by the way, is much better placed than the one on the older Highlight).
During the X-90 phase of Strong's manufacturing, it appears that they elected to use the same philosophy in these lamps as well, at least in later phases of manufacturing. Earlier X-90's did not have the dog-house behind the reflector that the later ones did.
On my next service visits, I will pay attention to see if there is any relationship between lamphouse design and the discoloration Mark mentioned.
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