Low output from moving lights - bulbs or something else?

[Stuart91]

A venue I work in has a set of four Chauvet 140SR hybrid moving lights. We checked them over recently and the light output on all four is poor, worse on some than others. 

My first thought was that they needed new bulbs. However, the lamp life seems reasonable - 580 hours on three, and a shade over 600 on the other. Venue staff are unlikely to have messed with the hour meters. 

The light output seems very uneven. Projecting a gobo straight down onto the floor, some segments seem brighter than others and there's a noticeable fluctuation in brightness in some parts. Reminded me of the look you'd get with a dodgy fluorescent tube with ripples and bright spots along it. 

I suspect the units have been left turned on for long periods of time. (Staff have a bad habit of leaving things turned on when they leave at the end of the night) From what I can see in the manual, the lamps get put into a lower power mode if the shutter is closed after a while, which probably explains why the lamp hours are relatively low for ~3yrs in place. However, I'd guess that there are still fans running in this mode, and presumably sucking all kinds of muck through the optics etc. 

They're mounted high enough up that I thought I'd canvass opinion here before getting a scaff tower on site only to find there's something I've overlooked. 

 

[Robin D]

I believe these to be discharge lamps that will fade to about 50% over time. It can also cause odd, and unpredictable fading of one colour as they can skew the temperature profile. Under pressure to get to a solution, we spent some time trying to sort what seemed to be a colour fading issue with a similar device only to find the issues were in the optics. A careful clean including the gobo wheel resolved the issues. It also stopped one of them overheating and shutting itself down. 

[Stuart91]

I've got more experience with projector bulbs, but I'd imagine the technology is fairly similar. They tend to be at 50% of their original brightness by the end of the rated lifespan. I'd hope that at ~10% of life these shouldn't have faded that much, so leaning more towards the "clogged with gunk" theory...

[sunray]

2 hours ago, Stuart91 said:

I've got more experience with projector bulbs, but I'd imagine the technology is fairly similar. They tend to be at 50% of their original brightness by the end of the rated lifespan. I'd hope that at ~10% of life these shouldn't have faded that much, so leaning more towards the "clogged with gunk" theory...

How much smoke is used in the venue?

[Stuart91]

15 hours ago, sunray said:

How much smoke is used in the venue?

Good question. Not huge amounts, it tends to be lighter haze, and only for certain events. It's not like a typical club environment where there are high-output machines running constantly every night. 

However, there's a fair bit of dust etc. in the air. Whilst the movers are well out of reach, the filters on some aircon units are filthy, and that's only taken six months since they were installed. 

[Robin D]

If these units have fans and filters, they will need a good clean then as well as the optics. The other thing to consider is that if the light source has been handled, the oil in the hands will blacken the glass and significantly reduce light output. Sadly no cure except replacement with more care.