May I put you on a dimmer?

Good afternoon,

I am new to stage lighting and work in a HS PAC. I am trying to figure out which items in our inventory should or should not be connected to a dimmer. A number of the items below have had "unusually" short lamp life, according to my co-manager and others who have assisted in the PAC.

The HS PAC has the following:
2 - Strand Lighting CD 80, currently outfitted with dimmer supervisors(? not sure what the units inside the CD 80 are referred to as)
20- Altman Zip Strip ZS (3 circuit)
20- Altman Star Par
20- Altman 1k 6" Fresnel
30- Strand Lighting SL

I was reading the manual for the Zip Strips and did not see anything relating to being able to connect them to a dimmer. I reached out to Altman who said they should not be on a dimmer. Yet my predecessors may have had them hooked up to dimmers since the PAC was built, at least for the past six years.

To reiterate I am trying to determine what items above may be connected to a dimmer without damage or short life. I am trying to determine this because our Zip Strips and StrandLight SLs keep burning out at a quick rate.
 
All of those fixtures are designed to be on a dimmer. I don't know who would've told you that the strip lights shouldn't be on a dimmer but that's how they are commonly used. The MR16 lamps in those have been used in dimmable track lighting all over the place. Maybe they thought you were discussing Spectra Cyc's or some other LED source, but everything you've listed are tungsten source fixtures.

When you have a high volume of lamp failures, the common things to check are the:

1) Make sure people are not handling the quartz globes with bare skin. The oil from your skin will cause damage to the lamp when it heats up. If your skin comes in contact with the quartz you should wipe it down with isopropyl alcohol.

2) Check the lamp bases and sockets for blackening, corrosion, or signs of arcing. If you see signs of this it is likely that the socket needs to be replaced.

3) Put a voltmeter on your circuits and see how much voltage is arriving at the receptacles you are plugging lighting into and compare it to the rated voltages of your lamps. If you are buying 115V lamps and running them at 125V then you may experience premature failures. I'm not super familiar with the CD80's but generally there are ways to limit the max level at the dimmer rack, and sometimes you can also have an electrician adjust the tap setting of the transformer feeding the dimmers to compensate for a consistent under or over-voltage.



The fixtures you have probably are somewhere around 10-15 years old. If you confirm people are not mishandling lamps and that the dimmers aren't driving your lamps at a higher voltage then it is likely that the sockets have lived a good life and need to be replaced.
 
Everything that Mike said. And replace lamps in the strips as soon as practical. The 12v MR16 lamps that they take are fine with 120v when there are 10 working lamps in a strip, but get progressively testy when they have to divide that voltage among 8 or 9 lamps, I believe.
 
Everything that Mike said. And replace lamps in the strips as soon as practical. The 12v MR16 lamps that they take are fine with 120v when there are 10 working lamps in a strip, but get progressively testy when they have to divide that voltage among 8 or 9 lamps, I believe.

Not so much testy as non functional. The entire premise is 10 lamps each of 12 volt, wired in series. Once 1 lamp blows, the circuit is dead.

The Altman Zip Strips are a nice design with a decent socket. Easy to replace if burned out.
 
If I might interject:

Start tracking lamp failures, replacements and maintenance, and general troubleshooting for the next several weeks/months. Try associating lamp failures, dimmer troubles, etc in terms of time; if you had a lamp failure in close proximity to the lamp being changed, that’s likely a mishandled lamp. Doesn’t take long to destroy a lamp from mishandling. If you’re having extremely consistent lamp failures (always after 20 hours of use, for example) you may be running into bad lamp batches; contact your distributor/seller. Intermittent issues affecting only one fixture? Sounds like a dimmer issue, might take out a module and sniff around for dust, blown capacitors, bad soldering, etc.

When you’re having issues appearing everywhere/randomly, it’s best to start immediately tracking data. Information is power, and being able to use the process of elimination will save you a ton of work and unnecessary expense later.
 
And replace lamps in the strips as soon as practical. The 12v MR16 lamps that they take are fine with 120v when there are 10 working lamps in a strip, but get progressively testy when they have to divide that voltage among 8 or 9 lamps, I believe.
You believe incorrectly. Since they are wiring, series , when one lamp fails, current stops flowing and the remaining lamps are unlit and unaffected. (Save for possibly weakened filaments as noted below.*)

To reiterate I am trying to determine what items above may be connected to a dimmer without damage or short life. I am trying to determine this because our Zip Strips and StrandLight SLs keep burning out at a quick rate.
ALL of the fixtures you listed use incandescent lamps and may be / should be connected to a dimmer. Are any of the fixtures used as worklight or left on at Full for long periods of time?

*As for the Zipstrip s, there's a philosophical approach that says when one lamp blows, one should replace the other nine as well, that they have weakened filament s. Not sure I agree, but seems to have been true with 28v ACL lamps in series of four.

As to the Strand SLs, are you using 300-hour or 2000-hour lamps? 115v or 120v version? What is the voltage at the lamp's socket? When a lamp does fail, is the filament broken, or envelope cloudy, blackened, or silvered? Are the lamp base's pins shiny, darkened, or corroded?
 
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there's a philosophical approach that says when one lamp blows, one should replace the other nine as well, that they have weakened filament s. Not sure I agree, but seems to have been true with 28v ACL lamps in series of four.
I used to take ACL's and other lamps that survived in series circuit blowouts and measure their current pass on the bench with a given test voltage, then match lamps into new sets that had the same current pass. The idea was, as the lamps age and tungsten is lost off the filaments, their resistance goes up and they draw less current. If you mixed in a new lamp, the old lamps end up dropping more voltage due to the higher resistance and quickly blow. If you can match them, the voltage drop is evened out and they last longer. Probably work with any series lamp.
Unfortunately, often when ACL's went, you would lose all four and the silver-sand fuse in the dimmer pack. (yea, it was the 80's)
 
?

*As for the Zipstrip s, there's a philosophical approach that says when one lamp blows, one should replace the other nine as well, that they have weakened filament s. Not sure I agree, but seems to have been true with 28v ACL lamps in series of four.

?

Not sure I agree with that concept either. Had heard it was the practice on Broadway shows that used the L&E MiniStrip, way back in the day when they were invented (late 1980’s ?). As a user of 12 units I just decided to ignore that and can’t say I ever noticed a bunch of lamps not going the distance and we did keep track as best we could. Bad sockets were/are a far more serious issue that made the early lamp failure issues somewhat moot.

Not an issue on the the Altman’s so far.
 
I used to take ACL's and other lamps that survived in series circuit blowouts and measure their current pass on the bench with a given test voltage, then match lamps into new sets that had the same current pass. ...
Makes sense for the 25-hour GE 4552, but I don't think it holds for the 2000-hour EYC. Not to mention the labor, and $34 x3 vs. $2 x9.
 
Makes sense for the 25-hour GE 4552, but I don't think it holds for the 2000-hour EYC. Not to mention the labor, and $34 x3 vs. $2 x9.
Halogen is the other issue. The old 4559's were incandescent. The filaments would "boil off" rather even and you would see the resistance increase. With Halogen, the tungsten gets redeposited, usually unevenly, so you end up with a very small weak spot, but the general resistance probably doesn't change much. Never really tried with Halogen. The Q4559 was just becoming popular when I retired from Rock.
 
I'm not sure how it might affect the strips, but one thing I've done is profile my incandescent fixtures down at the controller. That reduces the maximum voltage the lamps will see and thereby extends lamp life. There are a few interesting threads that can be found with some searching on the subject. Extended life lamps as I recall differ only from their non-extended brethren in that the filament is rated for a higher voltage (130 instead of 115 or something) and has a similar effect of modifying the profile. There is debate on constantly running your lamps at intensities less than 100% as it might prevent the halogen cycle that JD was talking about where the tungsten inside the glass envelope gets redeposited on the filament, but I think the consensus landed on having a full on macro on the controller that could be run at regular intervals to restore the lamps might help with that. I too am a HS TD and trying to preserve lamp life is helpful for both my limited time and budget.
 
The number I hear the most is 80%. If you have these lamps below 80% for long periods, the tungsten will start to deposit on the envelope giving it a silver looking coating. The thing is, once you get below 50%, very little tungsten will be evaporating and the lamp will last a very long time. I don't know if any real studies were done, but I suspect there is a "danger" range between about 60% an 80% where if the lamps are parked there long enough you may radically reduce lamp life. In real life, that would be rare so I never gave it much thought. The greatest danger of this would be in architectural lighting applications.
Once the deposit on the envelope starts, I don't think the lamp can be recovered as you would have to take the envelope up to a temperature that caused the tungsten to evaporate again.
 
Is it possible that someone put non dimmable LED retrofits in the striplights, and in turn they fail after long exposure to dimmed loads?
 
Thanks for the information. I have been out from illness and a HS Robotics event which I help mentor.


1.) Bare hands more than likely contributes to most of the failures with the Zip Strips. I try to wear nitrile gloves however my co-manager and predecessor would handle the dome/rim bare handed. None of us touch the bulb around the filament.

2.) A number of strips have sockets which show signs of corrosion and pitting, from what I am able to tell they may be the original sockets. The socket may even have a pin from the lamp still stuck in it. When funds permit I plan on replacing the sockets.

3.) Our drama groups rehearse about 3 hrs a day during the weekday and longer on the weekends for a month or more, we have three clubs which use it throughout the year. I do not know what level they keep the lights at during rehearsals.

4.) The Strand SLs have had a mix of bulbs in them. The most recent ones I was replacing were FLKs 115v but I am not sure on the life. I read a thread on here which talked about the differences between FLK, GLA and a couple others then I ordered GLA 115v 575w bulbs.
 
*As for the Zipstrip s, there's a philosophical approach that says when one lamp blows, one should replace the other nine as well, that they have weakened filament s. Not sure I agree, but seems to have been true with 28v ACL lamps in series of four.

My thought on this is not that the remaining lamps are weaker, but they are the same age and have the same hours, so you end up replacing one every couple of days until they are all new. If it seems like the lamps are close to their rated life, I'd rather replace them all at once, then have the same light have a burnout several times during a run.

Same thing with hard to reach areas. I have a huge box of used lamps that still work. They came from a museum where it is a big ordeal to hire a lift and move it around in the exhibits, so EVERY lamp gets changed on a schedule because it's not practical to replace them as needed.
 
You believe incorrectly. Since they are wiring, series , when one lamp fails, current stops flowing and the remaining lamps are unlit and unaffected. (Save for possibly weakened filaments as noted below.*)

ALL of the fixtures you listed use incandescent lamps and may be / should be connected to a dimmer. Are any of the fixtures used as worklight or left on at Full for long periods of time?

.....

They do use the stage lighting while building sets and doing miscellaneous work either side of using it for rehearsing.
I found a two post work light which I put in there for the time being as our normal lights are roughly 60ft up on the ceiling and are not able to be reached by our scissor lifts.
 
All of those fixtures are designed to be on a dimmer. I don't know who would've told you that the strip lights shouldn't be on a dimmer but that's how they are commonly used. The MR16 lamps in those have been used in dimmable track lighting all over the place. Maybe they thought you were discussing Spectra Cyc's or some other LED source, but everything you've listed are tungsten source fixtures.

When you have a high volume of lamp failures, the common things to check are the:

1) Make sure people are not handling the quartz globes with bare skin. The oil from your skin will cause damage to the lamp when it heats up. If your skin comes in contact with the quartz you should wipe it down with isopropyl alcohol.

2) Check the lamp bases and sockets for blackening, corrosion, or signs of arcing. If you see signs of this it is likely that the socket needs to be replaced.

3) Put a voltmeter on your circuits and see how much voltage is arriving at the receptacles you are plugging lighting into and compare it to the rated voltages of your lamps. If you are buying 115V lamps and running them at 125V then you may experience premature failures. I'm not super familiar with the CD80's but generally there are ways to limit the max level at the dimmer rack, and sometimes you can also have an electrician adjust the tap setting of the transformer feeding the dimmers to compensate for a consistent under or over-voltage.



The fixtures you have probably are somewhere around 10-15 years old. If you confirm people are not mishandling lamps and that the dimmers aren't driving your lamps at a higher voltage then it is likely that the sockets have lived a good life and need to be replaced.

Thanks for the information Mike. I will try to implement the preventative measures and replace the sockets which have failed.
I reached out to Altman regarding the dimmers because our drama clubs purchased some LEDs recently. The manual with the LEDS explicitly states not to put them on a dimmer, as there is one built into the unit. This made me try to find out if the Altman manuals had the same warning.
 
@Peter Mahoney
That's specific to LED's, which generally want to be on constant power. Some LED fixtures are designed for a little more tolerance and won't be disturbed if run on dimmers so long as the dimmers are parked at full output and all of the dimming is performed over the DMX inputs of the LED fixtures.

The very rare exception to this is the ETC S4 retrofit kit. This is a white non-color changing LED that can be dimmed through the AC outlet (no DMX), or over DMX (AC power @ full). However DMX is always preferred because the dimming curve is smoother, especially at lower intensities when fading to black.
 

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