Film-Tech Forum ARCHIVE: Spots developing on Osram bulbs

This is topic Spots developing on Osram bulbs in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mark J. Marshall (Member # 1409) on 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!

Posted by Mark Gulbrandsen (Member # 72) on 03-14-2003, 10:42 PM:

The best thing to do is to NOT use Osram lamps. They're no where near as good as they used to be.....Go with a brand name like Christie, LTI, or Superior Quartz. You'll have alot less trouble.
Mark @ CLACO

Posted by Adam Martin (Member # 641) on 03-14-2003, 10:55 PM:

What kind of spotting is it? A discoloration of the quartz, black residue, milky white or blue residue? That last one is from a gas leak. Can you post a photo?

Posted by Paul G. Thompson (Member # 655) on 03-14-2003, 10:59 PM:

Adam beat me to it.

Post a picture. Maybe some of us can tell you what they are.

Posted by John Hawkinson (Member # 1135) on 03-14-2003, 11:27 PM:

You don't need to order it, Osram's document Technology and Applications: XBO Theatre Lamps is up on their web site (linked to from the discharge lamps section).

--jhawk

Posted by Larry Shaw (Member # 388) on 03-15-2003, 04:50 PM:

Mark,
I have a couple bulbs that look like this:

Is this the same damage you're getting?

Posted by Michael Schaffer (Member # 1204) on 03-16-2003, 07:08 AM:

That lamp is obviously overheated. Probably from bad electrode connections.

Posted by Rick Long (Member # 213) on 03-16-2003, 08:48 AM:

I too, have noticed similar discoloration on some of our bulbs.
Mark, which Strong Console Model is this?

Posted by Tim Reed (Member # 137) on 03-16-2003, 01:00 PM:

I used to get that, too, years ago at a particular theatre. Never did figure out what it was. Just concluded it must have been the Osrams, since they began to fail more than Christies did.

Posted by Paul G. Thompson (Member # 655) on 03-16-2003, 01:05 PM:

I think it is defective manufacturing and quality control. If you recall correctly, the metal ends of the xenon bulbs are designed to turn yellow if the temperature parameters are exceeded. I forgot what the figure was, but as far as I know, it is still being done that way by bulb manufacturers.

Larry, that looks like a "High Milage" bulb, and by looking at the anode, it might have been driven too hard. Is there a possibility some crud and corruption may be falling out of a dirty stack onto the bulb and burning its way into the envelope? Just a thought...

Posted by Rick Long (Member # 213) on 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.

Posted by Robert Golding (Member # 746) on 03-17-2003, 03:11 AM:

I've had this problem with Osrams. I use to run 4k bulbs years ago and had this problem start at around 900 hrs. It's caused by overheating or in my case a bad ground to the lamphouse. I've since stopped using osrams and will only use Christie's. They haven't given me a problem for over 10 years.

Posted by Mark J. Marshall (Member # 1409) on 03-17-2003, 09:17 AM:

Wow. Once again, I ask a question and go away for two days only to find tons of responses! Thanks for the help guys. To answer a few of the questions posed here...

quote:
What kind of spotting is it?

It's a milky white sometimes speckled spotting usually about the size of a small fingerprint (which is what we originally thought it was until we took extreme measures to ensure no one was touching them - only to have the spots show up anyway). Our engineer noticed that the spots are actually on the INSIDE of the envelope under the Cathode (not sure how I missed that before). The best way I can describe it is to quote our engineer: "It looks like a drop of milk fell off the back of the cathode and landed inside the quartz envelope."

quote:
Can you post a photo?

Good idea... I'm working on that. I'll get back to you.

quote:
which Strong Console Model is this?

I'll be at the theater tonight, and I can give you an exact model number. Off the top of my head, they are Strong Super Highlights, and they're about 12 years old. I'm not sure about the other theaters that our manager called, but I'll find out.

Thanks again!
Mark

Posted by John Pytlak (Member # 331) on 03-17-2003, 10:48 AM:

Either something is subliming and depositing itself on the inside of the quartz envelope, or it is a type of vitrification (recrystalization) of the quartz. In either case, it looks like the lamp will be more prone to catastrophic failure.

Posted by Tim Reed (Member # 137) on 03-17-2003, 11:43 AM:

Yes, any dark spots on the envelope also conduct more heat. It's a chain-reaction.

Posted by Larry Shaw (Member # 388) on 03-17-2003, 02:56 PM:

Paul,
The markings (I call it "soap scum") are entirely on the inside of the envelope. This XBO7000W bulb has about 300 hours, it is the first bulb run in this LH. Now a second XBO7000W has done the same thing at about the same hours. Irem N3180 w/filter. Plenty of airflow. A second identical setup has had no problem. Go figure. Osram has them now, I'm waiting for their comments.

Posted by Adam Martin (Member # 641) on 03-17-2003, 04:53 PM:

Larry, have you actually measured and compared the airflow in the two lamphouses? If there is too much airflow in the front of the lamphouse, the cathode end (that sits inside the collector, where airflow is more restricted) will become overheated and cause the quartz on that end of the lamp to vitrify and will also cause instability in the arc. Ideally, air will move evenly throughout the entire lamphouse. Additionally, a slight defect in the collector may be directing energy back onto the lamp, which would also cause the overheating of the cathode and/or quartz.

Milky white or blue residue inside the bulb is tungsten oxide, caused by the tungsten electrodes reacting with oxygen that has seeped into the bulb. I've never seen a lamp where only parts of the quartz had this residue ... usually the whole thing goes in a single reaction. Maybe the bulb was not completely evacuated in the manufacturing process, leaving just enough oxygen inside to cause spotting from a small reaction. Are the lamps in which this is happening all from the same lot, perhaps?

Posted by Mark J. Marshall (Member # 1409) on 03-17-2003, 05:55 PM:

quote:
If there is too much airflow in the front of the lamphouse, the cathode end .... will become overheated and cause the quartz on that end of the lamp to vitrify

Could a mis-aligned reflector cause vitrification in the way that you describe?

Posted by Adam Martin (Member # 641) on 03-17-2003, 06:40 PM:

Anything that could cause excessive heat energy to be directed at the lamp envelope can cause the quartz to crystalize. I don't know how misaligned the collector would have to be for that to occur, though.

Actually, now that I think about it, when the quartz crystallizes, it is devitrifying. My bad. [Smile]

Devitrification usually occurs when the quartz is depurified (oil from fingerprints, etc.) and heated. If you have cleaned a lamp with alcohol after having touched it, are you using denatured alcohol or that crap from the drug store? (Osram recommends "spirit", whatever that is. Come to think of it, a prayer might just help [Smile]

) Are you wiping all the residue off with a lens tissue?

Posted by Mark J. Marshall (Member # 1409) on 03-17-2003, 08:03 PM:

quote:
are you using denatured alcohol or that crap from the drug store?

THAT can be a sore subject around here. [Roll Eyes]

I think I forgot to mention that our sister theater down the road recently received a bulb with the mysterious white spot already on it... still sealed in the box! It's currently on its way back to Osram for inspection along with the remains of another one that blew up - presumably as a result of the spot.

Edit: Here's a picture of one of our spotted bulbs:

Posted by Mark J. Marshall (Member # 1409) on 04-08-2003, 03:22 PM:

I now have ANOTHER bulb, this one is a 3K bulb with about 250 hours on it, that looks exactly like the photo above. These are all different projectors, in fact, different multiplexes.

I'm thinking there HAS to be some QC problem at Osram, or a bad batch of bulbs, or something. Although would "bad batch" imply one group of one kind of bulb? We have 2Ks and 3Ks with this problem.

Posted by Jack Ondracek (Member # 1466) on 04-08-2003, 04:43 PM:

quote:
from Adam:
(Osram recommends "spirit", whatever that is.

It's call "Everclear". Find it at your local liquor store! [thumbsup]