Hey all, I got a question, if I'm not mistaken, the LL 6500K 400 watt T15 lamp should have a 20000 hr life correct.

Now my question is, these lamps aren't like an incandescent bulb, they don't just up and not work, for the most part (though I did see what happened to Durachko's ceramic lamp), correct, so what really happens?

Do they just slowly get dimmer? Does the color temp start shifting?

I really need to know as today, as I was trying to tweak some things, I noticed that all of a sudden I see that my image started to color shift to more of a yellow the the white light.


Anyone that knows the answer please let me know.



EDIT: Also, I know I did some things that I do believe you should not do with a lamp, I broke in my lamp for many hours in a horizontal position, but has been relocated to a vertical mount, I did see this happen (color shift) when I first switched the position of the lamp. But it seemed to correct itself, but it has stayed in the vertical position since then.

It is possible that a MH lamp will simply just not work one day, in that it will not fire, but there are many signs of failure as well. Color shifting, dimming, "unstable" lamp running are all signs that a lamp may be reaching the end of it's life. I've also noticed a "wandering" arc when changing a T15 lamp from the horizton to vertical position. I believe my lamp was rated as a horizontal so I didn't worry too much about it and went and purchased a vertically (base up/down) lamp for running vertical. I'm not sure of the rating on the LL T15 lamp, but I understood it to be universal mount. How long have you been running the lamp ? How long has it been in the vertical position ? How long was it horiztonal ?

Well it ran horizontally for approximately... I don't know... 50hrs, and it has been running the vertically for I would guess 35hrs. These are very conservative numbers, I guess they could be as high as 100hrs and 85hrs.

But thats what makes me wonder, if it really is supposed to have has such a long life span, then it should be no where near the end of it's life.

Now I could be mistaken, which has been known to happen from time to time, there are salts or other such things inside the arc tube correct? So could it be possible that in my last round of adjustments I could have knocked loose some of that particulate, that might now need to go through another burn in cycle of 10 to 15 hours?

I'm pretty sure you can shift the color by adjusting the bulb relative to the fresnel, since the change in color seems to have corresponded to the adjustments you made that would be my guess of the cause. Try putting the bulb/other stuff back where they were if you can.

This thread may be related...
Orange And Blue

Yellowing can happen from a number of other things, including exposing the fresnels to excessive amounts of ultraviolet.

Before blaming the lamp, make sure that the lamp's colour has changed. If so, it should be obvious if you lift the lid of the projector a bit. You can also check for the colour of your fresnels -- but do that with the lamp off. Do not expose yourself to direct light from the lamp for any length of time.

Well it seams that maybe I just knowed some particulate loose in the arc tube when I bumped the buld with the reflector while it was very hot.

Cause since I have been burning it for a number of hours now, the colors seem to have stabilized again.


Thanks guys for all the advice.