I just wanted to start this thread as ive read almost all of thisforum and still haven't found an answer to my question and assume others out there would like a place to discuss the topif of inially aquiring a bulb.

I just got in the mail a LL lighting set and wired everything up for a test jsut to make sure it all worked. I've read all the forums of other people having problems with their lights, but mine doesn't seem to match.

my eballist keeps kicking every few seconds, trying to startt the light, but the light just won't start. Every once and a while i'll get a blue spark, but thats it. i real before hand of plugging this thign up and when i first litl the bult it took quite some time, but eventually lit. I let it burn for about 45min so it would settle in, since these bulbs aren't meant to be run for shrt times, but now it won't light agin. I've let it run for 20 or so min intervals, but by that time i start getting worrried about the ballist working so i have shut it down.

my question is, what is everyone's first time experiance with thesee bulbs and how do they handle. Do wee have aproceduree for best testing these bulbs? if not, what is the reccomendend procedure? is my situation unusual? whats the best position to first fire up a bulb in?

I think that this is a critical question that is not addressed enough. I believe that the lamp should be run in one and only one position, that being the position that it will be in the projector.

My thinking is as follows:

These lamps are designed to be installed and run in the same position for their entire life. It is known that these lamps require a break in period. The mechanics of the break in is such that the metal salts in the arc chamber settle into the most optimum position after so many hours of use.

So: We can conclude that any time the lamp is re-oriented, it will have to undergo another break in period. (a lamp that is not broken in can be difficult to start) Also we can assume that if we can determine the exact burn position used during the factory test, we might be able to reduce burn in time and starting difficulties by positioning the lamp as close to the origional position as possible.

Personally my lamp mount is positioned so the heavier mercury deposit is at the bottom as I assumed that this would be the best indicator of the lamps initial burn position.

Prepositioning the lamp may be overkill and unnecessary; but I think that it is very important to burn the lamp in only one orientation if possible to have the greatest longevity.

Anyways; That's my theory.

I think your line of thinking is pretty correct. There are lots of chemical things going on inside there that I don't understand, but I'm sure they don't like to get moved around much. I myself won't even strike the thing off until I get it installed in the box, so I don't have to move it again.

Ok,

So it seems that we have come to a conclusion that these bulbs need to first be fired, and remain in the same position their entire life. But that the position is dependent on their orentation in the pj.

Now, you mention a factory test. I don't think these bulbs are factory tested. Before mine was first struck there was the metal elements in the bulb moving around and it was clear; after firing it, the elements seem to have become evenly dispersed on the inside of the bulb and give it a cloudy discoloration.

Now, the question I've been wondering about. What are peoples average time for the bulb to fire up? I've read on here about some peoples bulbs taking up to an hour to strike an arc. I'm curious as after i let my bulb burn in for about 45 min yesterday. I let it cool, but then could not get it to fire again. I let it try and arc for about 10 min, with only seeing a little blue arc about 3 or 4 times, but not enough to hold the arc, it would jsut flash.

These bulbs have what they call a hot restrike time, as I am sure you know, so there is a time period that you MUST wait until you can successfully strike the bulb again. I am sure just sitting there after you turned it off, trying to get it to strike again is not good for your bulb. Find some instructions somewhere, I am sure they exist, and follow them.

Not sure I can agree with you on this one DR.

Almost all Light bulbs are designed to just screw in and burn till they die. MH are no different than fluro or incand in that respecet. come to think of it ... there are not many that do move. Maybe those ones at the giant furnature outlet that whip around and light up the sky on opening day...

with MH, each time the bulb strikes the metals and salts are vapourized into a gas plasma. every time it cools most condense back out. I can see no reason that a fixed position has anything to do with how the gas plasma burns. Obviously verticle or horizontal will have different light output because of the running shape of the arc stream but which position it cools and evaporates in should have little or no effect on its ultimate life or output. who knows?, Salts constantly condensing on the same location every day might actually be detrimental to the internal glass structure. Perhaps if a MH bulb was "rolled" every 2 days it might actually last 2 times longer. This is not really an option in most applications because nobody wants to climb a ladder and turn evey sinlge warehouse light on a weekly bases.

Just me thinking. :)

Kirk

Well you could be correct and I greatly respect any opinion that you have stickgrip. It is only a theory but it is based on much reading I have done on metal halide lighting. What led me to this conclusion is something I read reguarding lamp burn in. I wish I could cite the source but I don't remember where it was. It basically said that the salts/metals in the arc chamber migrate to their optimum location during burn in making for easier striking of the lamp. Heat and gravity affect where the salts end up when the lamp cools.

From this, I have made the assumption that any disruption in the position might make the lamp difficult to strike. It is a possibility though, and since we are using these lamps in an unconventional way with no real information on this to go by, it seems to me to be a prudent precaution.

The question really lies in what affect (if any) that gravity or the earth's magnetic field has on the path of the arc as the lamp is being struck. If it has any influence on the arc path as it moves to the opposing electrode, then I feel fairly confident that I am correct.

I agree stickgrip. The orientation of the condensed salts makes little difference and molten salts break down the quartz arc tube and tungsten electrodes in time. It's much more important to take care of the electrodes by bringing it up to operating temps before shutting down and letting it cool enough before restrike. I'm thinking the lamps often have a poor argon fill or the electrodes are in poor condition which causes problems with ionization for striking and stabilizing the arc. It just seems odd that so many are having problems with their pulse strike setups. The Icecap/Eiko setup from Alan Staples gives me problems every once in a while. I've never had a problem with my old magnetic ballast which makes me wonder sometimes. I'm thinking my rare intermittent problems are caused by the FC2 sockets as the contacts seem poor to me with little surface area touching.

Hmmm... this is interesting ...needs more research.

If the deposition of the salts has no affect on a lamps ability to successfully strike, then what exactly is being "broken in/burned in".

Vertical, horizontal, base up, base down etc.
I don't know what bulb you are using but maybe you have it mounted in the wrong orientation. Just a thought.

I think the orientation may play a role in the ability for re-strike as in a vertical position the salts/metals are going to tend to settle on the electrodes. In a horizontal position i would assume they would tend to settle on the side of the lamp. These salts/metals may cause difficulties in holding an arc in the pulse ballasts.

I really don't see what the need for a burn-in time is. These lamps reach their maximum temperature in a matter of minutes, after that, there should be no changes in the physical characteristics in the lamp. once max temp is reached, it should be safe to turn the bulb off. so, a burn-in time of 5 min instead of 45min.

The real concern would be that the bulb would be fired again in the same position that it was shut off, so that the sediment would be in a optimal position.