8mm Forum: GS 1200 XENON Reflector repair

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Posted by Mark Norton (Member # 165) on April 04, 2013, 03:26 PM:

I have a nice new toshiba lamp in the Xenon but a very dim picture due to the lamp reflector which was damaged after a lamp explosion with the previous owner.

I am having trouble finding a replacement reflector and after consulting Kingsview optical the existing one is beyond repair.

Has anyone used something else in place of the original reflector?

Posted by Lee Mannering (Member # 728) on April 04, 2013, 03:47 PM:

Mark. Is it not possible to have it re mirrored? Our Elmo Xenon lamp exploded in the 90’s and I seem to remember we had the mirror re coated prior to fitting the lamp. Fingers crossed yours didn’t explode in front of 200 people in a packed auditorium as with ours. PM sent.

Posted by Vidar Olavesen (Member # 3354) on April 04, 2013, 03:49 PM:

You contacted Bill Parsons?

bill(at)bparsons97(dot)plus(dot)com

Posted by Mark Norton (Member # 165) on April 04, 2013, 05:28 PM:

Thanks Lee and Vidar, Bill does not have one & local re-mirroring company reckon it's too far gone. Lots of glass missing but what is left in there is solid, so perhaps it still might be possible to repair.

Posted by Vidar Olavesen (Member # 3354) on April 04, 2013, 06:31 PM:

I am not sure how this lamp is built, but you mean a new lamp wouldn't solve the problem? Is a new lamp without the reflector? I haven't gotten my Xenon machine yet (next week maybe ... Grin) and I am not sure how they're constructed.

Posted by Matt McBride (Member # 3311) on April 04, 2013, 06:52 PM:

Xenon lamps and reflectors are discrete components. Because xenon lamps need more cooling, need magnet stabilization if they are burnt horizontally, and a special way to ignite the bulb, it made sense to construct a housing in which the reflector is part of this housing. Then one only has to replace the bulb when it's past its prime.

Also Vidar if you haven't handled xenon bulbs before and you wish to replace them yourself you need to be extra careful when handling it. Never touch the glass with your bare hands. Only were approved gloves when handling the bulb and only handle it on the metal ends. Never put any stress on the glass either. You need to make sure you were some sort of face shield as well. A ballistic shirt may or may not be necessary depending on the size of the bulb. Absolutely make sure you do not install it backwards, otherwise the second you strike the lamp it will explode.

I think I covered most of it. Anyone else please add things I may have missed. Vidar, I know there are lots of things to remember and it may seem dangerous, but with proper handling changing these bulbs are not a big deal.

Posted by Maurizio Di Cintio (Member # 144) on April 04, 2013, 07:31 PM:

Hi. How can you tell when it's time to change a xenon bulb before it explodes? My xenon machine still has the original Toshiba bulb (which I prefer because its arc is steadier than the ones manufactured by "Superior Quartz"). Light is really brilliant and white and I tend to use the lower setting as a rule of thumb, switching to the higher only when projecting in 'scope. The lamp strikes in a few seconds usually, sometimes it may take a little longer, sometimes a little shorter time. But I never stress it too long, never exceeding 4-5 secs when it doesn't ignite at first strike. So I am veru cautious... Any hints? Thanks.

Posted by Matt McBride (Member # 3311) on April 04, 2013, 08:37 PM:

The best way is to go by the rated hours. You may or may not have that handy. A lot of projectors that operate xenon bulbs have a lamp meter to count the hours. If this is a 35mm system or a theatrical 16mm, the lamp meter would be on the lamphouse or console. If you know the model number you may be able to look it up. As bulbs get older, they become harder to ignite and may not ignite on the first strike. Also as bulbs get older they start to cloud up, making the glass look gray to black, however this depends greatly on how often the bulb is run in duration. Most xenons, and guys correct me if I am wrong, 1000 watts and under should last for about 2000 hours before they should be changed, keep in mind this is just a rough guess. If you don't have a lamp meter on your machine you can take a guess on how many movies you have watched and multiply by 2, an average length of a movie, and that will get you in the ball park of the current hours.

As an example, let's say you watch a movie once a week, there are 52 weeks in a year so that is 52*2= 104 hours per year, let's round up to 110 hours, for various things, such as initial setup and alignment etc. Then 2000/110 = approx 18 yrs. If it were me in this example, after 12-15 yrs, I would probably change it, because the picture will be a lot dimmer, maybe even after 10 I'd change it. It's a personal preference. Though you can use this example to estimate where you current bulb life is based on how many movies you think you have watched since you've had it. Again knowing the bulbs rated hours is what is best.

Keep in mind though, the older and more used the bulb gets, the more unstable the bulb becomes and the more likely it can explode, so even more care should be taken when removing a spent bulb.

Posted by Maurizio Di Cintio (Member # 144) on April 04, 2013, 09:45 PM:

Hi, Matt and thank you for your response which is cedrtainly very sensible.

The problem is twofold in that the GS 1200 Xenon does not have an hour-counter facility, and I have owned it since only september 2009. During these years I have screened a lot fewer films than a full-length per week. But I have no idea as to the previous owner's usage of the machine: I don't even know who this person was, since I bought it totally overhauled by a specialist. That's why I was asking if there are some clues to look for relative to the bulb approaching its lifespan.

Posted by Matt McBride (Member # 3311) on April 05, 2013, 12:37 AM:

Well you can look for clouding in the bulb. The darker the glass the closer it is to its lifespan. Though this is not always failsafe. There is another thing you can look at, is to see how pitted the anode and cathode ends where the arc actually goes across. If they are pretty pitted out, then the bulb may be out the door. It seems like you have put a lot less than 400 hours on it just judging on your comment

quote:
During these years I have screened a lot fewer films than a full-length per week.

And since you got this without knowing the hours, I would almost say if you can buy a new bulb and just change it now. In my opinion it's probably better to spend an extra few dollars now to replace that bulb new and start fresh so you can keep track of the hours, than have the headache of hearing the bulb explode and to find reflector damage.

Getting used bulbs is always an issue unless the seller knows how many hours are on it. Just as an example, my current 1000w bulb for my 35mm setup, I bought used, but I was told it had low hours on it. The seller didn't know exactly the hours, but once I reach 1000 hours on this bulb and once the bulb starts to struggle to ignite after this time, I'm getting a new one, just to be precautous. Though of course bulb not igniting on the first strike can be from other factors as well.

The point is I don't want to risk reflector damage as replacement/resilvering is a lot more expensive than the bulb. Unfortunately with these arc lamps there are a lot of factors that go into them, and there can be many things that happen when they reach the end of their life. There is a nice paper in the warehouse section under tips on film-tech.com called Analyzing xenon bulb failures. Here is the link: Xenon Bulb Failure Analysis This will give you a very good understanding of what can happen to these bulbs as they age.

Posted by Lee Mannering (Member # 728) on April 05, 2013, 08:33 AM:

Matt is absolutely right in that users should take great care if contemplating changing Xenon lamps. Ignorance is bliss as they say and the ionised Xenon gas within is at very high pressure enclosed in the glass. As for the age of a lamp I usually go by how quick they strike up (probably not much of a guide) or looking at the electrodes for messy wear. Sadly as mentioned Elmo didn’t include a usage clock as per cinema lamp houses so we have to keep a record in the diminishing brain cells or on paper.
I’m not quite sure what caused the Xenon lamp explosion way back when in the 90’s but it sure went with a big bang and minute glass particles eventually dropping from the sky into the audience. It could have been not allowing the lamp to cool properly in previous use before moving, or perhaps the glass was faulty in some way who knows. I’m guessing most of us only used the Xenon Elmo for big shows where the bigger picture is required and the rest of the time use a decent Eumig Stereo or a standard GS1200 to save wear and tear on a expensive to maintain projector if it all goes wrong.
[Eek!]

This of course is another plus point for film against Blu-Ray projection as audience participation in Xenon lamp explosion is a real crowd pleaser.

Posted by David Ollerearnshaw (Member # 3296) on April 05, 2013, 04:13 PM:

Here's one exploding from You tube Mind you they do look like a set of twits.

Posted by Maurizio Di Cintio (Member # 144) on April 05, 2013, 05:06 PM:

David, Lee and Matt thank you all for your sound advice which I'll treasure. Also I have had a look at the bulb catode/anode (not easy without removing it from the reflector) and they seem OK.

I have a spare bulb from SQ which is a clone of the original Toshiba bulb meant for the GS (sadly non lobger manufactured); they are somewhat brighter and whiter but I found out they tend to develop somewhat higher temperatures, resulting in a slight, hardly perceptible deformation of the outer surface of the rear film conveyor: though I might live with it, what actually bothers me is the arc generated buy these new, cloned bulbs is somewhat less steady than the original, which is noticeable in brighter areas of the image. So I'd like to delay as long as possible replacing the Toshiba bulb. Does anybody know of a source for these Toshiba bulbs? Or for the reflector? Or who can have them remirrored? Again thank you!

Posted by Alexander Vandeputte (Member # 1803) on April 05, 2013, 05:48 PM:

Maurizio, have you tried the clone lamp that Ugo Grassi had made in China. I have one and the lamp strikes easy, has a very stable arc and runs less hot than the Toshiba that was in the machine before. Even better, Ugo sells them for a very attractive price.
It is true that the reflector is a weak point in the xenon machine. I think it should not be too difficult to have a new mirror made, but some more knowledgable people probably know more about that.

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