Xenon lamp Explosion !!!

[Steve Lee]

About 3 weeks ago I was running through a crate of 16mm films that I didn't know that I had, when there is an almighty explosion from the projectors lamp house. Fortunately I had just walked out of the room when this occurred, or else I think I would still be connected to a defibrillator at this moment. Over the years I have unfortunately been witness to several large 4k + xenon's ending their lives in this spectacular way, which is OK. After a couple of week when your hearing starts to return and you can press the ignition / igniter button once again without trembling with the fear of it happening again, it's only first hand experience that teaches the respect of what this type of lamp is capable of. but I never thought a 500w xenon would go this way, more of a POP than an explosion!

Once I had removed my family of cats from the ceiling I decided to go and see what the damage was. Opening up the lamp house my heart sank, not only had the lamp gone but it had taken out everything with it, The glass mirror and the striking igniter. It's quite ironic that the week before I was rejoicing for the fact I had found a company that has a supply of new slate runners for this machine after 20 years + of searching for them, and now this happens.

After hours trawling the web to see what type of money I am looking at to replace this lot, it's a no go. 2000+ euros! The mirror alone is 850 plus tax and shipping. So it was back to the drawing board.

I decided to look at what other discharge lamps were available, but more importantly what type of fitting did they go into. it seems that most of the fit stage and effect lanterns, so this is where my search begins. It must have been a stroke of luck as I started searching through Ebay somebody in France was selling a Clay Paky professional gobo effect projector, that is designed to project onto buildings and has a 300w HTI lamp house. I made an offer and got it for 70 euros complete!

The next problem was how to mount this unit onto the projector so it could be aligned. I looked at many pictures of the machine from the sales brochures, and back in the day these were sold with many options and one of them was a rear bracket for a full size lamp house. So I started to build something similar that used the fixings on the projector for this bracket.

There is still some work to do on this project in a way of refining it but it works. It is amazing how technology has come on in the lighting department over the years. The original 500w xenon produced around 14,000 lumens and this 300w HTI produces 23,000 lumens without the need of a walloping DC rectifier!
In a way it's a shame this didn't happen years ago, when I think of all the money I could have saved on the electricity bill.

[Lee Mannering]

Hi Steve. It happened to me at a much reported public Super 8 film competition where I was luckily stood behind my Elmo GS1200 Xenon projector and the lamp exploded over 200 people. I was not over exaggerating when I said we had glass fired up into the sky in the cinema then dropping into the audience around me, not something to be taken lightly.
The power behind these Xenon lamps exploding is enormous as I witnessed with the qualified Elmo engineer saying "Yes we have had a few go and luckily no injuries" I will never forget it. The glass in the Elmo Xenon was scattered around the innards and one hell of a mess = new mirror, lamp plus a few components.
As a result I learned to stand behind my Xenon's at all times during a show rather than at the side...

[Alan Rik]

I had always heard that when the Xenon lamps have a hard time striking than its time to have them replaced. Was this happening to yours Lee? Or did it just one day give up the ghost so to speak?

[Maurice Leakey]

Xenon projection lamps tend to dim over time. That's when they should be replaced.
Most lamps have a stated approximate life span, this is why some lamp houses have an hours calculator which can be reset to zero when a new lamp is fitted.

[Nick Regan]

Steve

I used to work in the entertainment lighting industry and most of the high end professional equipment used "Discharge lamps" These lamps are sold with a certain lamp life telling how many hours the lamp should be used for. ( Normally 2000 hrs) After this time the lamp should (in theory) be changed wheather it is working or not.

Of course Nightclub owners due to the high costs of replacement lamps normally ignore this lamp life and leave the lamp until it expires one way or the other.

One of the ways they fail is they wont strike up, another is they switch off and have to cool down before relighting (hot restrike) but the most impressive fails are the exloding lamp.

These can be a regular occourence and the manufacturers now enlose the lamp inside a metal shield to contain most of the glass if it blows and include a lamp used clock on the uniit control.

When they go, a HMI575 such as used in an Eiki P4000 projector can be heard exploding over the sound from a 50K sound system.

I suppose the moral of the story is when you buy a lamp, note the date and how long the lamp is run for. Also its worth checking them visually as if a lamp has gone black or if it has gone silver this is a sign the voltage to the lamp is too much or too little. Bite the bullet and replace when the hours are up.

Some things to note iare the colour tempreature of the lamp. The same spec lamps in the 150 - 200w discharge range can come in 2 types 1600k or 3200k This is the difference between a yellow and a blue light (Daylight or Tungsten) You would need a Starter, looks a bit like a larger flourescent tube starter and a Phase Capacitor, this was once described to me by a lighting manuafacturer as the thing that stops the lamp draining all the elecricity from the street. The actual circuit for powering these smaller discharge lamps is quite simple. Oh and include a cooling fan.

Nick

[Steve Lee]

One of the main problems was the lamp house didn't have a clock on it, and I had no idea how many hours the lamp had on it. Also there was no tell tell signs that this was going to happen. Also working with them professionally for many years you get to know the warning signs when this is about to happen, but there was none of this. The lamp always struck very cleanly and always first time, there was no pitting on the cathode and anode also no blackening on the lamp and no colour change.

The only possibility that I can think of is there may have been a power surge, which is quite common where I live, as we are the only house in our road that doesn't have a three phase supply.

I guess it was just one of those things, but in a way it has done me a favor as the new HTI lamp produces a much cleaner and brighter light that is blinding compared to the xenon, and uses half of the consumption. Also you can pick the lamps up for about 50 euros, so it's a win all round.

[Lee Mannering]

Maurice is correct although I did not know that a few decades ago.
Dim = replace.
In my case the lamp was only 3 years old and very modest use around 60 hours