projector lamp life

[mattywizzy]

looking for some advice -

in our church we have 2 digital projectors, the lamp life seems to be quite short, 1500 hours vs 3000 hours as stated by the manufacturer, BenQ. Its been suggested that the lamp life is low because of how cold the worship space gets when the room is not in use. Is there any credibility in this?

 

If so are there any recommendations for keeping the projectors warm? they are currently suspended from the ceiling, so the ideal solution would be one where we don't need to access them regularly, although this is possible if needed. Initial thought is to get some kind of form fitting case which still allows adequate ventilation and the ceiling mount to be fitted.

 

Any suggestions greatly appreciated,

 

Matt

[sleepytom]

3000 hours is simply unrealistic - you'll notice that it is only the cheap projector brands which *claim* to have bulbs that last 3000 hours. Most professional hire companies replace bulbs at 1000 hours and replace the whole projector at 3000 hours.

 

putting some foam round the projector will do nothing to lengthen the bulb life.

[mattywizzy]

thanks for the reply.

so does the cold not affect the lamp life?

 

do we simply need to budget to replace the lamps every 1000hrs?

[Simon Lewis]

Matt,

 

Cold is unlikely to be a factor, as a far as I'm aware. Condensation on optical parts could be though.

I can't find the figures right now, but manufacturers expect only ~ 50% of bulbs to last the stated hours. Of course, it's likely that the light outpout will decrease with time, and other components in the optical path may degrade too (especially LCD screens).

 

As mentioned above, hire companies know that there comes a point where getting enough light out of the unit is too expensive, so it may be easier to budget for a new device than to keep buying new bulbs and being unhappy with the result.

 

Simon

[oilyspark]

Its been suggested that the lamp life is low because of how cold the worship space gets when the room is not in use. Is there any credibility in this?

 

I doubt it. Extreme cold can cause other parts of the proj to malfunction but anything less than a few hundred degrees is 'cold' as far as the lamp itself is concerned. Repeated switching on and off, especially restriking while hot and shutting down during the first few minutes of operation can shorten life though. What is the actual failure mode of the lamps you have had? Poor output / failure to strike / uneven colour?

 

The actual life time (normally quoted to 50% failure) is governed by the design of lamp and how hard it is run in the particular projector model. 3000 hours is a bit ambitious even for a lamp run at the low end of its rated range. And as Simon says, those that make it to that age will be giving dismal output by then. A projector lamp I use in quantity, rated by Osram for 750 hours, typically goes out of spec in my application after about 200-300 and I always replace by then. Some don't make it to 100.

 

30 years ago we'd have been using something like the GE MARC 300. Same sort of thing but rated life 25 hours!

 

Lucien

[tony g]

I honestly don't see the cold as a major factor unless the lamp is starting very cold and therefore forming condensation on it's surface (although this should evaporate evenly and cause no problem), lamps rarely last the specified burn time as most lamp makers do this test by switching them on and leaving them till they fail, then averaging several such tests to give a nice round number. burn time on a T1 was officially 200 hours - more like 30!

 

heres a tip from crompton though, if you use TH / IQ lamps in your stage lights, run them at full for 1/2 hour a week this will either A) increase the lamp life as claimed by the makers or B) increase lamp sales :)

[Pete McCrea]

I'd agree with all the above. 3000 hours is very optimistic, and will be likely quote in 'Eco' mode where the lamp brightness is markedly decreased to gain the extra hours.

 

I think the best plan is to ensure that the units are struck as little as possible, and not struck then turned off after short periods, as well as budgeting for more regular lamp changes. Having had the Panasonic Rep in, it might also be worth looking out for new units that feature AC lamps that supposedly can provide better lamp life and less output drop as the voltage is alternated over the electrodes as opposed to being constant.

[david.elsbury]

heres a tip from crompton though, if you use TH / IQ lamps in your stage lights, run them at full for 1/2 hour a week this will either A) increase the lamp life as claimed by the makers or B) increase lamp sales

There is actually truth to this.

When you run a tungsten halogen lamp, the carbon that burns from the fillament burning off the filament gets re-deposited back onto itself. But when you dim the lamp, it doesn't re-deposit properly- it deposits on the glass I think. So running the lamp at full it completes the process- a regeneration cycle I think it's called and gives you a longer life.

 

No doubt some one else can fill in the blanks if required :D

[greenalien]

How often do you clean / service your projectors? Bad airflow caused by dust buildup will significantly reduce lamp life.

[mattywizzy]

thanks for all the replys, really appreciate the assistance. We've had the lamps in use for around the 1500 hr mark so really we should be expecting to replace the lamps. A clean and service would probably be a good idea as well. Again many thanks

Matt

[timtheenchanteruk]

the 3000 hrs is usually on low power, continuously run, optimum conditions etc, iirc each strike of the lamp reduces its hrs by at least 1 each time.

[kitlane]

heres a tip from crompton though, if you use TH / IQ lamps in your stage lights, run them at full for 1/2 hour a week this will either A) increase the lamp life as claimed by the makers or B) increase lamp sales

There is actually truth to this.

When you run a tungsten halogen lamp, the carbon that burns from the fillament burning off the filament gets re-deposited back onto itself. But when you dim the lamp, it doesn't re-deposit properly- it deposits on the glass I think. So running the lamp at full it completes the process- a regeneration cycle I think it's called and gives you a longer life.

 

No doubt some one else can fill in the blanks if required :D

 

In the Tungsten Halogen Cycle, the tungsten (not carbon) that leaves the filament combines with a halogen to form a tungsten-oxyhalide which does not form a black deposit on the lamp envelope. In a normal domestic bulb (remember those?) the lamp blackens due to deposition of tungsten. The tungsten-oxyhalide breaks down at the filament, redepositing the tungsten back onto the filament.

 

This process only works at a high enough temperature. If you dim the lamp the temperature decreases and tungsten may be deposited on the inside of the glass envelope. By running the lamp at full you 'burn off' the tungsten from the envelope, which will certainly make the lamp brighter and probably help increase the filament life a little.

 

However, as video projectors don't use Tungsten Halogen lamps it's all a bit off-topic. Basically - what everyone else said. 3000 hours is a very ambitious lamp life.

[greenalien]

We've had the lamps in use for around the 1500 hr mark so really we should be expecting to replace the lamps. A clean and service would probably be a good idea as well.

 

1500 hours is a long time between clean-outs, unless the projector is installed in a very clean room! At the very least, it needs a good vacuuming every 1 - 200 hours if it's in an averagely-dusty environment (cooling fan and lamp compartment (carefully!!)).

[Paul28]

3000 hours is simply unrealistic - you'll notice that it is only the cheap projector brands which *claim* to have bulbs that last 3000 hours. Most professional hire companies replace bulbs at 1000 hours and replace the whole projector at 3000 hours.

 

putting some foam round the projector will do nothing to lengthen the bulb life.

 

I second this. A totally misleading thing to say to consumers.