Dreading the moment when all of the bulbs go out....

[JLNorthGA]

We started off last year with all brand new Source Four instruments with new bulbs (Ushio HPL 575WX/115V) and Altman 65Q Fresnel instruments (BTN 750W/120V P28S). Most of our events are concerts. They don't use the 65Qs (unless it's a large group and they need overhead lighting).

I've only had to replace one bulb (knock on wood) - due to me jostling an instrument while aiming it. The circuits are pretty good and the power seems to be very stable. We replaced a lot of our wiring before we started using our new equipment.

I haven't really kept track of the hours (though I have kept track of the shows). The concerts require maybe about 3-4 hours of lights. The plays require about 50-70 hours what with rehearsals and performances.

The lights are not run at 100%. We have a Sensor 3 dimmer rack.

Should I be stockpiling bulbs? Waiting for the "500 hour life" to come to its end?

 

[sk8rsdad]

It's hard to predict the true life of a lamp for the reasons you stated. I order replacement lamps by the carton and always have a minimum number on the shelf. Lamps tend to fail in waves but not en masse so we just let them burn out naturally. Most fail during lamp check when starting cold. Rarely they fail mid-show and there's almost always a workaround for the dead fixture. By the end of the season I might have gone through 2 boxes of each size (375W, 575W, 750W). We don't log lamp hours because we don't have to worry about hundreds or thousands of instruments.

 

[MNicolai]

If life expectancy is a concern, get the 2000-hour HPL lamps for the Source Fours, which it appears you already have from the "X" designation in the name.

Lamps, it's a crapshoot. Sometimes they live longer than you want, other times not nearly as long. Another factor is that they last quite a deal longer if they're not run at a full. You could get a bit more lifetime out of your concert lighting by running the at 95%. I believe we have ours topping out at 93%.

If you're counting the hours, it sounds like you have a limited budget. My recommendation is when you have the money, buy more lamps. You don't want to be low on funds and suddenly need to make an order, and lamps are the sort of thing if you don't use them now, you'll use them in the months and years to come.

It's good to have a emergency stockpile as well. If you work with a number of different people, keep your general stockpile accessible to everyone, then keep an extra 5 or so in a different location. That way when someone comes to you concerned about being out of lamps, you have a few spares you can hand out for that immediate time and are alerted to the fact that it's time to put another order in.

Biggest issue we see is that people replace a bunch of lamps over the period of a few months or a year and nobody tells the guy who does the purchasing that the lamp stock is low or out. Then one more lamp goes out and it's an emergency because the stock is exhausted and no one has time to drive to a dealer to pick up more and a 3-4 day shipping time on a new order is too long.

 

[techieman33]

Those HPL's are rated at 2000 hours, with a good possibility of getting more life than that out of them since they aren't running at 100%. It wouldn't hurt to stock heavy on spare lamps at the beginning though, then over time you'll get a better idea of what you really need to keep on hand as spares. I would keep track of how often your changing lamps though, it will help you forecast your needs better in the future. I would even keep track of which fixture it is, and who replaced the lamp. That way if there is a problem with a bad fixture, or maybe a tech is doing something wrong during install you can catch it a lot faster.

 

[JFR]

Should I be stockpiling bulbs? Waiting for the "500 hour life" to come to its end?

I usually stock between 10-20% of my inventory in spare lamps. So if I have 100 S4s I'll have between 10-20 spares. I also restock by the dozen.

 

[Les]

Should I be stockpiling bulbs?

Why would you want to do that?



Maybe not so much "stockpiling", but the 10% sounds about right. Most theatres order lamps by the box (usually 12 or so), and that's a good minimum number to have on hand of any given type for smaller-to-medium houses.

 

[derekleffew]

You can maybe extend your lamp life by running a preheat cue (see the thread https://www.controlbooth.com/threads/preheating-conventionals.6431/ for the controversy/argument/debate) prior to lamp check.
Other electricians prefer to bump each cold lamp to full at the beginning of the day, the theory being if it's ready to go, better it fail during lamp check than during the show.
Don't fret over it. Keep in stock new lamps for about 10% of each fixture type and you should be more than fine. (Some would say 5%.)

 

[DELO72]

You can't track life on these. If you run your lamps at the rated voltage, at full, then you can plan to track the hours. If you are using them in a normal show condition where they are at 34% in one cue, full in another, 85% in the next, etc. there is no way to plan for when they will fail. When you burn a lamp at less than 100%, you are underpowering it and increasing the life by not driving it as hard. Remember- the life rating on lamps is the hours at which 50% of a production lot has failed, when tested in the following manner-- 60 minutes on, 10 minutes off, at full power. It's almost a meaningless rating when compared to actual use of the lamp.

Do what these fine folks suggest and have some spares on hand. They won't all go at once unless you get some crazy power surge.

 

[GoboMan]

When I do my lamp/channel check, I always like to bring all the lights up to 50% on a 10-second fade, that way you can see that they're all working and it can avoid lights blowing out from the sudden surge of power from being cold for the last 20 hours. Then, once I've given them a couple of minutes to get hot, then I turn them off and perform my individual channel check. I've never had any problems with lamps blowing out during a show, but mostly during focus and during a lamp check, as mentioned in a previous post.

My theatre has an inventory consisting of Source Four 750s, Source Four Juniors, Altman 360Qs, and 6- and 8-inch Fresnels. We try to budget our lamp supply so we always have no less than 5 spare lamps available for each type of instrument. In my opinion, to "stockpile" a huge number of spare lamps is costly and unnecessary, as with proper care and maintenance of the instrument, you can get long life out of lamps.

However, my theatre does have an outdoor summer stage that we perform at, and I have had lamps blow out considerably more often out there than on our indoor stage, and that's due to weather and spiders deciding to make nests overnight in the sockets of the Source Four lamps. Side story: Last year I did a lamp check on our outdoor stage and one of the Source Fours started smoking out the back of the instrument. I immediately cut the power, of course, and when I investigated I found a charred spider carcass in the lamp housing. Fun stuff!

 

[JLNorthGA]

Why would you want to do that?



Maybe not so much "stockpiling", but the 10% sounds about right. Most theatres order lamps by the box (usually 12 or so), and that's a good minimum number to have on hand of any given type for smaller-to-medium houses.

I might get hungry?? No wait - those aren't eating bulbs - they are flower bulbs.