Many thanks for the explanation. Our projectors were installed second-hand and reconditioned, so as I say, I think the most likely explanation is that the ammeter installed in the lamphouse when new went bust at some stage and was replaced by someone who didn't know that there was any difference and just thought that an ammeter was an ammeter, full stop.

By looking at that bulb with 6000 hours, I would recommend a power supply filter check, as well as the power supply operating parameter check, be performed as you suggested. Since all three bumps are the same size, I doubt if there is a diode problem.

Three phase AC ripple got into that thing, and by observing how severe the bumps look, the problem developed over a long period of time.

Please tell us how three phase ripple would cause three mushroom growths, as seen in Randy's photo. Does the plasma ball move around in sync with the phases, perhaps by magnetic force? Interesting phenomenon.

I honestly don't know. It is an interesting phenomenon. All I know is it does happen. The bumps are 120 degrees apart.

I have seen this happen with bulbs used with single phase phase power supplies, also, but they leave 2 bumps 180 degrees from each other.

The three phase problems seem to cure themselves if the filter capacitors are renewed, or if the power supply is tapped for a lower current setting.

The phenomenum you are addressing happens quite frequently in the XPS-20-03 ORC power supplies operating at maximum rated output. Apparently, the capacitors are not large enough in capacity to do adequate filtering within that parameter.

Normally we change them out at about 1800 hours, more or less. I have let them go up to 2000 in a pinch. (When the new lamps are on backorder, etc.) When we found this one I took one look and said, "What in the blankety-blank is this? I took this picture for my "Hall of Shame"... examples of things that you shouldn't do. I was going to post it a while back but I hesitated because I didn't want to be accused of "putting people down". The only reason I posted it now is because it was topical.

Needless to say, "The names have been changed to protect the innocent..."

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

I had another place that kept telling me that the lamp wouldn't strike-up until about the 10th "crack". I kept telling them to change the lamp. They kept saying, "No, that isn't it." 3 or 4 times they call me up over a 3-4 month period with the same complaint and I kept telling them to change it. They never did.
I was there on a PM visit and they told me the same story. My answer was, "Go get your mask and gloves." By the time he found them I had the lamphouse undone (to the point of needing the mask and gloves.) I made HIM change the lamp while I watched. 10 minutes later we strike it up... WOW! It worked! I wonder how come?

Turns out that lamp was almost 4,000 hours old!
Every time I say to myself, "Now, I've seen everyting!" I turn around and there's something else!
After about 2-3 months of this kind of junk NOTHING pisses me off anymore.

As a reminder, xenon lamps should be smashed before they are disposed of.

Never throw away an intact xenon bulb. Some airhead dumpster diver may pull it out of the trash and say, "This is neat", not knowing how dangerous they are. If that thing blows up in their faces, the theater could be held liable.

It should always be handled with caution and common sense.

Never assume anything.

Most accidents happen out of carelessness, and not paying close attention to what you are doing.

Actually I was going to make a fictional movie where someone calls the theater with a "Xenon bulb threat" (as opposed to a bomb threat) and the whole theater is quickly evacuated. The manager does not meet the callers demands so they decide to blow up the xenon bulb which they have hidden in the theater. The entire complex explodes sky high in a sequence that makes the building explosion in Terminator 2 look like a firecracker.

It could happen!

If you use the Ideal Gas Law: PV=NRT

• P= Pressure
  
• V = Volume
  
• N = Amount of gas (in moles)
  
• R = Ideal Gas Constant
  
• T = Temperature (Degrees Kelvin)
  

Now we can cancel out V, N and R because we are not changing them. (The amount of gas and the volume of the bulb are the same.) We are left with P and T. We can just make them into a ratio.

P at room temperature is 147 pounds and we know that room temperature is 295 degrees K. If the lamp goes up to 300 deg. C when it is hot that would be 573 deg. K.
573 / 295 = 1.94

Multiply the "cold"pressure by 1.94...
147 * 1.94 = 228.92

The answer is that a xenon lamp has more than 200 pounds pressure in it when it's hot.
Of course if the lamp gets hotter than that the pressure would be more but the theory is the same, just plug in different numbers.

What I ask people is, "How would you like a piece of razor sharp glass hitting you in the face with 200 pounds of force?"