# Preheating Conventionals?



## gafftaper (Dec 5, 2007)

In the recent thread about someone blowing a bunch of lamps in a Strand SL, the idea of running a preheat macro was suggested. I'm curious if anyone does this on a regular basis as part of their preshow? A comment about not running cold lamps was made in that thread. But when you consider it in terms of how hot they get at full, aren't room temperature lamps also quite cold? Let's face it the difference between a lamp from the refrigerator and a lamp that's room temperature is insignificant compared to the insane temperatures that filament will reach in seconds. Anyone know if there's any real evidence that preheating does any good? Do you do it?


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## zac850 (Dec 5, 2007)

One of the first MEs I worked under always did this, and I picked up the habit from her. On most of my shows, I will create a preheat macro (or timed sub, or cue, depending on the console I'm using). Usually just takes all conventionals to 30 slowly, and then turns them off after like 30 seconds.

I've worked under other people who say don't bother, it doesn't do much.

I actually wonder about the benefit of it, has anyone ever done a sudo-scientific study to see if it helps or not?


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## icewolf08 (Dec 5, 2007)

Temperature shock is a very real issue. It is the same concept that causes a glass to shatter if cooled very quickly from an extremely hot temperature. I always run a warmer before I do channel check. My preshow routine includes taking all the channels in the show to 20% over 5 minutes, this warms everything up very slowly, and gives me time to get organized in the booth, hit the bathroom, and make my way down to the stage to get out RFU and do channel check.


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## soundlight (Dec 5, 2007)

I run everything at ten percent for a few minutes, which generally gets things nice and warm, and also allows me to check for gel fading and check instruments for bad lamps.


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## SteveB (Dec 5, 2007)

Macro 5 on my Express/Emphasis - Sneak Channels 1 - 258 at 25% in a 5 count. First thing I do when I come in on a show or setup call.

Steve Litterst at Univ. of Delaware called this a "Yankee Check". Ask him why, I have no idea, but that's what I call it now.

Steve Bailey
Brooklyn College


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## icewolf08 (Dec 5, 2007)

SteveB said:


> Macro 5 on my Express/Emphasis - Sneak Channels 1 - 258 at 25% in a 5 count. First thing I do when I come in on a show or setup call.
> Steve Litterst at Univ. of Delaware called this a "Yankee Check". Ask him why, I have no idea, but that's what I call it now.
> Steve Bailey
> Brooklyn College


You know Litterst? Cool.

I have heard it called a "Yankee Check" (probably from Litterst) or a "Broadway Check". Has something to do with being impatient and not wanting to do a full channel check, like us Yanks. I still do a full channel check though.


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## JD (Dec 5, 2007)

Ahh! The preheat issue again!

Preheat is a good thing that can become bad real fast. Running lamps at 5% for a few minutes on a cold show before kicking them full is a very good idea. Get the filaments just hot enough to almost visibly glow red. If the equipment if fresh off a truck, getting the glass a little hot is also good. Another weak area on lamps is the glass to metal seals that can be quite big on large lamps. warm is good.

That being said, I know of theaters and architectural systems that leave a high idle on 24/7 and this is very bad! The amount of power wasted can be amazing. Also, any visible output means that tungsten is vaporizing off of the filament, but probably the lamp is too cool for the redeposit cycle to work, therefore, the vapor will deposit on the quartz of the lamp greatly reducing the lifespan. 

As you can see, like anything else in life: A little is good does not mean a lot is better!


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## Grog12 (Dec 5, 2007)

JD said:


> Ahh! The preheat issue again!
> Preheat is a good thing that can become bad real fast. Running lamps at 5% for a few minutes on a cold show before kicking them full is a very good idea. Get the filaments just hot enough to almost visibly glow red. If the equipment if fresh off a truck, getting the glass a little hot is also good. Another weak area on lamps is the glass to metal seals that can be quite big on large lamps. warm is good.
> That being said, I know of theaters and architectural systems that leave a high idle on 24/7 and this is very bad! The amount of power wasted can be amazing. Also, any visible output means that tungsten is vaporizing off of the filament, but probably the lamp is too cool for the redeposit cycle to work, therefore, the vapor will deposit on the quartz of the lamp greatly reducing the lifespan.
> As you can see, like anything else in life: A little is good does not mean a lot is better!




Yeah I've done the 5% in either outdoor situations or places where the AC is cranked way too high.


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## Lightingguy32 (Dec 5, 2007)

Hmm.. Preheating, this issue comes up at our highschool all the time, and I have to yell at the board op to preheat the lights every single time unless I am the board op. Preheating is recommended since it prevents filament shock from destroying your filaments (high inrush current on a cold filament).


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## DarSax (Dec 5, 2007)

Snap. Since last year (when I did it religiously) I totally forgot about preheating. Thanks for the reminder


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## avkid (Dec 5, 2007)

It's wicked easy to do with the Horizon software, but the Lightronics board doesn't like me so I can only get half of them up at a time.
5% for 10 minutes.


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## Footer (Dec 5, 2007)

Really it depends what I am doing if I pre-heat or not. If I am doing a channel check, I always try to. Now... HPL tend to benefit, but the real savings come in 1k and 2k lamps, preheating is essential on these larger lamps. If I am doing a show that has 2k lamps I always insist that we do a pre-heat in the cue previous to the lamp coming up just to save the lamp (on most newer consoles, this is easy to program in as an auto move while dark command).


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## SteveB (Dec 5, 2007)

icewolf08 said:


> Has something to do with being impatient and not wanting to do a full channel check, like us Yanks. I still do a full channel check though.



I don't really consider it being impatient. It achieves 2 things. 

1) It gets the lamps warm and avoids cold shock

2) It allows me a walk around to see if any lamps are out. As it's the first thing I check (if the macro runs, I'm also now aware that there are probably no real console issues - we leave ours on 24/7), I know right away that I need to assign crew for a lamp change and can inform the SM immediately at the start of the call. 

I'm generally able to see burnouts in saturated colors as well, but only on certain units. I still hot up the MR16 cyc lights to full for a real burn-thru test, as example.

As I rarely do shows that run more then 1 event, I don't generally need to check for slipped focus issues, so usually have no need for a step-by-step channel check. If it's an event running a few days, I'll follow up with a "system" focus check (usually group call ups) that turn on FOH Pinks, then FOH Blues, etc... to look for slipped units. 

SB


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## fosstech (Dec 5, 2007)

We generally do not preheat small lamps here since we really don't have many problems with premature failure. I generally do preheat all 1k and up lamps. We recently put a rule into place with our 5k fresnels that they should always be preheated before bumping to full. With the 5kW DPY lamps being so expensive, a little insurance goes a long way. But let me tell you, when the huge filaments (they're the size of toaster coils) in one of those fail, it makes a pretty spectacular work of art on the inside of the large envelope.


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## avkid (Dec 5, 2007)

SteveB said:


> (if the macro runs, I'm also now aware that there are probably no real console issues - we leave ours on 24/7)


Hmm..I hope you have it well ventilated.
Power supplies don't like that.


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## Pie4Weebl (Dec 5, 2007)

yeah I tend to like to pre-heat fixtures most of the time I just preheat everything at 20 and run around and check for burn outs.


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## gafftaper (Dec 5, 2007)

So it sounds like most of us are doing some sort of pre-heat. The question is however, is there any data that says it's doing any good? 

I like the run them at 5% idea so they just start to glow... as soon as you start getting light it seems like you are cranking them too high. The whole relative temperature issue concerns me. It seems like it's a longer distance from cold to glowing than it is from glowing to full. It may not be 100% but that filament is freaking hot at 10%. The fact that you have the filament glowing at all means it's jumped to a dramatically higher temperature. Almost seems like it should be 0-5% over a couple minutes then slowly up to 10%-15% for your lamp check. 

Still would like to see some real data.


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## David Ashton (Dec 5, 2007)

"pre -heating lamps is a myth, which wastes a great deal of power and probably reduces lamp life, why? well a filament has a very low thermal mass, it goes from cold to white hot in a second or two and back to cold in a few seconds, it does not store heat, it would be useless if it did.A little preheat is unavoidable because all normal dimmers "leak" a few volts, and as earlier stated at low level the quartz cycle does not kick in.I have done experiments with this but I have to go out on a job and will give a detailed explanation later.


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## SteveB (Dec 5, 2007)

avkid said:


> Hmm..I hope you have it well ventilated.
> Power supplies don't like that.



The Express has had one PS replaced, but it wasn't a heat issue. The Express also has no fans and I was told years ago there was no real reason to shut it down as long as it's on a good UPS (that was the advice from ETC). Our building power is fed underground so we don't see lightning hits either. The Emphasis is in a enclosed box with vents and a temperature sensor to activate cooling fans as needed. I do sometimes shut both down if there not used for more then a few days, such as over Christmas or in the summer. In general we use the system every 2-3 days, for a few days in a row, thus it's time effective to leave on so as to allow the RFU control without having to open up the console position (rear orchestra). 

SB


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## David Ashton (Dec 6, 2007)

Please consider, a 1000 watt 240 volt T19 on a dimmer{for 120v thinkers just halve all the figures} It has a cold resistance of 3.8 ohms and a hot resistance of 57.6 ohms. A typical dimmer will feed 1.65v at "0" and drive .35A putting 2.24 W into the lamp of preheat.
@ 13V you can see the barest glow in the filament and are drawing .96A and 12.6W 
@30V you can see a real glow and are drawing 1.5A and 45W
at 60V you begin to get some output but at 1/4 voltage you are drawing 2A or nearly half the "full" current
@80V which is 1/3 voltage you are drawing 2.3A which is more than half the full load current and is also the point at which the dimmer starts to interact with the other dimmers on other phases.
This is why running all your dimmers at 1/3 is the worst thing you can do to your neutrals. 
Now there is a benefit in Pre-heating 2k and 5k in the previous cue, in effect you are moving them up the dimmer curve, but I have experimented with lamps and the increased resistance only lasts for a few seconds with 1/2k and a couple of minutes with 2k"s.
The thermal mass of a theatre lamp has to be as low as possible to enable it to light up and dim quickly, and pre-heating is not logical, especially when all your dimmers are "leaking" a few watts of heat anyway, so by all means turn on your lights to check them but be aware you are not helping to increase their lives and are probably shortening them and wasting a hell of a lot of power in the process.


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## Lightingguy32 (Dec 6, 2007)

Never forgot to do a preheat after I had a special blow (HPL lamp) on an electric that wasn't easily excessable the day before a show. Was not fun, now I have a preheat macro ran through for both preheating and dimmer check.


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## gafftaper (Dec 6, 2007)

allthingstheatre said:


> Please consider, a 1000 watt 240 volt T19 on a dimmer{for 120v thinkers just halve all the figures} It has a cold resistance of 3.8 ohms and a hot resistance of 57.6 ohms. A typical dimmer will feed 1.65v at "0" and drive .35A putting 2.24 W into the lamp of preheat.
> @ 13V you can see the barest glow in the filament and are drawing .96A and 12.6W
> @30V you can see a real glow and are drawing 1.5A and 45W
> at 60V you begin to get some output but at 1/4 voltage you are drawing 2A or nearly half the "full" current
> ...



See now that makes a lot more sense to me than the anecdotal evidence presented. My feeling is by the time you get that filament to glow at all, it's already made the most dramatic part of it's temperature increase. If you're preheating at 20% you've completely blown past the range where the filament is starting to warm up. However you are running the lamp too low to take advantage of the quartz cycle. So it seems to me that it's making things worse. If there was a way to accurately take the lamp from 0-5% over 5 minutes then it would make more sense to me, but dimmers aren't that precise.


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## David Ashton (Dec 6, 2007)

Pre- heating has become a ritual act, it is taught in universities, and while it could be a part of religious studies, it has no logical or evidential basis but I find people will cling to the practice regardless.


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## Charc (Dec 6, 2007)

If there's one thing I've learned from this thread:

Check lamps often.


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## derekleffew (Dec 6, 2007)

charcoaldabs said:


> If there's one thing I've learned from this thread:
> 
> Check lamps often.


Industry standard is once a day before the first performance, even in Las Vegas; but I'm not sure about Broadway. SteveB?

Here's another argument for NOT pre-heating: if a lamp is near the end of its life due to a weakened thin portion of its filament, isn't it better to "bump to full" during the lamp check, so it can be replaced before the show and not fail during?

Myself, on long running shows I write a cue that takes everything up to from 0 to 10% in five minutes, which gives me time to get to the stage and roughly check for burn-outs, then runs an effect which brings each channel to full for roughly 10 seconds to check for focus (some channels longer, some shorter), then puts me in Q1 for House Preset. I've still had lamps blow this way, so it may be the best of both methods.


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## SteveB (Dec 6, 2007)

derekleffew said:


> Industry standard is once a day before the first performance, even in Las Vegas; but I'm not sure about Broadway. SteveB?



I'm sorry to say that I have no idea what's done on B-Way. I would take a guess that they do a system check for focus issues as well as blown lamps and fried color. I would imagine it could take forever to go thru the plot channel by channel. I think the typical Broadway crew call is 7PM for an 8PM show on a typical 4 hr. show call that ends at 11, thus time is an issue when you've got a half hr. to find problems and fix them.

SB


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## David Ashton (Dec 7, 2007)

Lightingguy32 said:


> Never forgot to do a preheat after I had a special blow (HPL lamp) on an electric that wasn't easily accessible the day before a show. Was not fun, now I have a preheat macro ran through for both preheating and dimmer check.


Sorry but your assumption that the lamp blew because you did not preheat has absolutely no validity, it blew because it was at the end of its life, we all try to explain things that fail but mostly it is just serendipity, of course we all do lamp checks before a show, that is normal practice but it should not be confused with preheating which I have shown to have no basis or benefit in fact.


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## Grog12 (Dec 7, 2007)

derekleffew said:


> Industry standard is once a day before the first performance, even in Las Vegas; but I'm not sure about Broadway. SteveB?
> Here's another argument for NOT pre-heating: if a lamp is near the end of it's life due to a weakened thin portion of its filament, isn't it better to "bump to full" during the lamp check, so it can be replaced before the show and not fail during?
> Myself, on long running shows I write a cue that takes everything up to from 0 to 10% in five minutes, which gives me time to get to the stage and roughly check for burn-outs, then runs an effect which brings each channel to full for roughly 10 seconds to check for focus (some channels longer, some shorter), then puts me in Q1 for House Preset. I've still had lamps blow this way, so it may be the best of both methods.



Having been in a good portion of the houses in Vegas I laughed at the 5 minutes to get to the stage because that's something of a minimum...(except for oh Stomp...)

As to your question I think the thought behind preheating isn't so much about lamps at the end of their life but about temp shock to the filament/envelope. An example might be throwing a bucket of hot water on the window of a car in Buffalo NY in Dec. (I do not advocate doing this.)

Like I said before I don't preheat unless I'm in an outdoor venue or a place where they crank the AC to unreasonable temps.

I like the macro you've got written but personally prefer to do check with a remote or another person.


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## jonhirsh (Dec 7, 2007)

What does it cost to preheat your lights? $0.00?

What does it cost to replace a lamp? 

Wouldn't you rather preheat, even on the off chance that it does nothing?

JH


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## gafftaper (Dec 7, 2007)

jonhirsh said:


> What does it cost to preheat your lights? $0.00?
> What does it cost to replace a lamp?
> Wouldn't you rather preheat, even on the off chance that it does nothing?
> JH



Still not convinced it doesn't do more damage than good. If you are running the lights at such a low level you don't activate the halogen cycle for any length of time it seems to me you are shortening the life of your lamps. 

Oh SHIP! We need you big guy!


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## David Ashton (Dec 7, 2007)

What does it cost to pre-heat lights?Well, multiply the length of time the lamp is burning by the watts it is consuming by the cost of the electricity, then allow for all the hours of the lamps life which are spend doing nothing useful just "warming" and the probable shorter life due to filament loss below the quartz cycle
Whilst one would need a computer model to be exact a reasonable estimate of the cost of pre-heating is $100's for a small theatre, $1000's for a large theatre and many millions for the USA as a whole.


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## jonhirsh (Dec 7, 2007)

Thats assuming that pre heating shortens the life span... all im saying is with out a definite answer... it couldn't hurt.

JH


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## David Ashton (Dec 7, 2007)

If you run the lamps for 15 minutes a night of course you are shortening their life span or more precisely you are using up that lifespan doing nothing except sitting there being warm.
Now while you are not paying for the power it is still a very major cost to the venue.
Doing things because we have always done them is a very powerful force.
Sometimes though we need to stand back and consider if the things we have always done make real sense.
I would suggest in this case there is no rationale at all for this practice.


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## avkid (Dec 7, 2007)

Hmm...we need to commission an experiment..
I'll write it up and post a summary.

first we need to define Preheat.
Any thoughts?


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## David Ashton (Dec 7, 2007)

Yes, if members could
1 give a brief summary of their pre-heat ritual
2 read their power meter during that ritual
3 read their power meter for the same duration of time without lights on
4 deduct 3 from 2 to determine how much power was used
5 tell us the cost of that much power
6 it would be informative if possible to measure the neutral current during the preheat.


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## avkid (Dec 7, 2007)

No, a controlled experiment is the only way to do this.
For which the neutral testing party will require:
Two brand new identical fixtures 
A simple two channel dimmer
DMX controller
Two lamps of the same batch
well regulated power
a reliable timing device

If we can get a manufacturer or a dealer to sponsor this by loaning equipment, I'll gladly conduct the test.

I will now swear that I have no affiliations with any lighting manufacturers except the following:
NSI/Colortran


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## David Ashton (Dec 8, 2007)

Avkid,We are trying to look at the big picture of how much power is used in the pre-heat process, your experiment only addresses lamp life at reduced voltage.


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## avkid (Dec 8, 2007)

allthingstheatre said:


> Avkid,We are trying to look at the big picture of how much power is used in the pre-heat process, your experiment only addresses lamp life at reduced voltage.


If you go back to the beginning, lamp life was the issue.


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## icewolf08 (Dec 8, 2007)

allthingstheatre said:


> Avkid,We are trying to look at the big picture of how much power is used in the pre-heat process, your experiment only addresses lamp life at reduced voltage.



But the reason that people preheat is because they think it extends lamp life. Therefore AVkid's proposal is the most valid. Power consumption is a non-issue if AVkid's experiment proves that preheating does not extend lamp life because we would all stop preheating our lamps thus not use as much power.


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## avkid (Dec 8, 2007)

Thank you Alex.


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## David Ashton (Dec 8, 2007)

Given that a lamp costs more money to run through its life than the cost of the lamp, power is a big issue[not to mention global warming and the need to reduce wasteful practices]


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## dj_illusions (Dec 8, 2007)

I have a funny feeling in our venue which is fully air condition with industrial kitchen, multiple small event rooms, offices, computers etc. preheating lamps for 5 minutes before a show is barely going to register on the power meter compared to the power that is been drained by all the other electrical equipment currently running.

If we are concerned about electricity, switch off the air conditioner for 5 minutes while preheating, im guessing this is going to save more energy than not preheating lamps for a whole year....

The issue was extended lamp life, i was trying to keep out of this discussion, i dont preheat lamps every time before a performance, but personally believe that preheating the lamps for a short period of time does improve the lamp life and also help condition the fixture, if you are stretching your filament before the show it is not put under as much strain when bumped to full as it would be without a preheat, i still see benefits in doing this and as many others have said even if it is not necessary it is a good practice as it forces you to do your lamp and gel check at the same time.


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## SerraAva (Dec 8, 2007)

Finally have time to put in my two sense. Anyway, great debate going on here. I am, however, with allthingstheatre. ETC makes HPL lamps for 115v, 120v, 230v, and 240v. The reason being that is the resitance in each of these lamps is different for each voltage lamp to get the 375w, 575w, or 750w you are looking for. 
750w/115v=6.52a; 115v/6.52a=17.64 ohms. 750w/120v=6.25a; 120/6.25a=19.2 ohms. 
Now let's try a lower voltage on a 120v lamp: 115v/19.2=5.99a; 115*5.99a=688.85w. 
And a higher voltage on a 115v lamp: 120v/17.64=6.80a; 120v*6.80a=816w. 

They make these different lamps to make sure you get the wattage you want at max voltage. Using to much voltage on a 115v lamps shortens the life. Using to little voltage can also have the same effect, because that lamp wants to be at 750w, 575w, or 375w. Thats what is was designed to operate at. Now went ETC says it takes a regular 750w or 575w lamp 300 hours till failure, thats mean time till failure. That means they took hundreds of lamps, ran them all over the place voltage wise, and ran them till they blew. The bulk of those lamps I am sure were at the recommended voltage, meaning they are most statistically significant. Its says +/- 10% at the bottom of ETC's page for lamp life, which is just statistical as well. I had an HPL blow within a couple hours of use before, and I am sure I have had them last longer then 1500 or 300 hours. Preheating, as stated, does nothing more then take lamp life off the lamp and use power. Why do I say this, because there are two laws that govern the universe, minimal energy, maximum disorder. Running those lamps slowly to whatever percentage puts them in a constant change of state, which things in the universe don't like, hence minimal energy. That lamp wants to run at whatever it was designed for, and thats the optimum lamp life for it.


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## Les (Dec 8, 2007)

I think that bringing the lights up slowly instead of bumping the first time before a show makes more sense than preheating.


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## icewolf08 (Dec 8, 2007)

SerraAva said:


> They make these different lamps to make sure you get the wattage you want at max voltage. Using to much voltage on a 115v lamps shortens the life. Using to little voltage can also have the same effect, because that lamp wants to be at 750w, 575w, or 375w. Thats what is was designed to operate at. Now went ETC says it takes a regular 750w or 575w lamp 300 hours till failure, thats mean time till failure. That means they took hundreds of lamps, ran them all over the place voltage wise, and ran them till they blew. The bulk of those lamps I am sure were at the recommended voltage, meaning they are most statistically significant. Its says +/- 10% at the bottom of ETC's page for lamp life, which is just statistical as well. I had an HPL blow within a couple hours of use before, and I am sure I have had them last longer then 1500 or 300 hours. Preheating, as stated, does nothing more then take lamp life off the lamp and use power. Why do I say this, because there are two laws that govern the universe, minimal energy, maximum disorder. Running those lamps slowly to whatever percentage puts them in a constant change of state, which things in the universe don't like, hence minimal energy. That lamp wants to run at whatever it was designed for, and thats the optimum lamp life for it.



Actually I believe average lamp life is calculated by running the test group of lamps at full until they burn out. This is because the lamp life rating is based on ideal operating conditions which for an HPL575/120v would be at 120v providing the most efficient halogen cycle. They take note of when each lamp burns out and then calculate the average life. The +/-10% says that in general lamps last within 10% of the rated life. Lamps do last longer if run under their rated voltage, we talked about that in another thread, and I believe Ship gave us a formula to approximate the change in lamp life when voltage is changed.

If you have had lamps last on the order of 1500 hours then you probably had an HPL "X" lamp which is rated to 1500 hours. While it may be possible for a 300 hour lamp to burn for 1500 ours, it is highly unlikely. There are many things that can shorten lamp life, so having a 300 or 1500 hour lamp only last half that is possible.

So, that still brings us back to the preheating question. It isn't a question if if preheating will make you lamp last longer than the rated lamp life, it is a question of if preheating will make the lamp last longer than not preheating the lamp.

Probably the ideal test would be to take two identical fixtures and lamps from the same lot, Preheat one at some low lever for some time and then turn both fixtures on to full in a 0 count. Let the fixtures burn for about 4 hours a day and repeat each day until one dies. I picked a 4 hour burn time because most theatres probably don't run their lamps for more than 4 hours a day. Running the lamps at full gives us optimum operating conditions, so we should get close to the rated lamp life.


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## gafftaper (Dec 8, 2007)

According to "Automated Lighting" the lamp life test is: they turn on 100 lamps and when the 50th lamp burns out they stop the clock and call it the lamp life. If that is true then there is a wide variety of potential life from the 2 hour lamp to the 2000 hour lamp.


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## avkid (Dec 8, 2007)

icewolf08 said:


> Probably the ideal test would be to take two identical fixtures and lamps from the same lot, Preheat one at some low lever for some time and then turn both fixtures on to full in a 0 count. Let the fixtures burn for about 4 hours a day and repeat each day until one dies. I picked a 4 hour burn time because most theatres probably don't run their lamps for more than 4 hours a day. Running the lamps at full gives us optimum operating conditions, so we should get close to the rated lamp life.


That is exactly what I proposed.
All we need is a dealer or manufacturer to supply the equipment.


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## David Ashton (Dec 8, 2007)

A very important fact which I have not seen mentioned is that
"the laws governing the relationship between voltage and lamp life in quartz halogen lamps only apply
at and above 80% of the rated voltage which is the point at which the halogen cycle kicks in". 
So all the pre-heating time is stripping tungsten off your filaments which is not replaced until you bring it up to over 80%


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## JD (Dec 8, 2007)

Found a neat PDF about light bulbs while researching the current thread. http://physicsed.buffalostate.edu/pubs/TPT/TPTDec99Filament.pdf

Here is a little quote from the article that I think we all overlook a bit:

--------(quote)----
"Halogen lamp filaments not only can be run hotter and more efficiently, but must be run at higher temperatures to initiate and sustain the halogen cycle. Therefore, for halogen bulbs, a very small tubular envelope made of fused silica (a noncrystalline quartz) is operated at temperatures up to 1200 8C (depending on bulb type and wattage), together with a high-pressure fill gas (about five atmospheres). To ensure full lamp life, halogen filaments should be run at least 20 minutes to initiate the halogen gas cycle and fill-gas convection."
---------(end quote)----

The "Overlooked" part is that little blurb that the bulb must be on for 20 minutes for the cycle to work! 

One thing more about preheats. Tungsten does not really start evaporating in mass until the filament is white hot. A 120 volt lamp run at 30 volts will probably outlive all of us! A friend of mine keeps mold out of his classic car that is in storage by keeping light bulbs lit in it. It is a string of three 100w lamps in series, which to date has been lit for 20 years and counting! (all original bulbs.)


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## gafftapegreenia (Dec 8, 2007)

I'd like to jump in.

This has been an interesting debate. I have three points.

I can see where preheating would be ineffective for HPL's and the like, but is there any merit to pre-heating, 5, 10 or 20K's?

It seems like that running your lamps at 80% or more on a regular basis would be better for life as it would help replace lost tungsten through the tungsten cycle. However, one must remember that tungsten is NOT replaced evenly. 

Preheating has been around for a long time. Might preheating have been effetive on the older tungsten, non-halogen lamps. I really don't see how it would have been, but just have the question in my mind.


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## David Ashton (Dec 8, 2007)

May years ago I worked in the Isle of Mann on a big resistance board and in the winter the grease on the bearings would congeal so I would run the lights at about 3 for 15 minutes to warm up the bearings and the operator.Unlike the filament of a lamp a resistance board has a large thermal mass and so stays warm.The basic question is" how long does it take for my pre-heated thing to return to its original temperature", if the answer is under a minute then clearly pre-heating it 30 minutes earlier is a waste of time, energy and lamp-life. QED


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## ship (Dec 11, 2007)

allthingstheatre said:


> A very important fact which I have not seen mentioned is that
> "the laws governing the relationship between voltage and lamp life in quartz halogen lamps only apply
> at and above 80% of the rated voltage which is the point at which the halogen cycle kicks in".
> So all the pre-heating time is stripping tungsten off your filaments which is not replaced until you bring it up to over 80%



Urr, please state where you got this info from. I don't think your reference is corrct in being used for line voltage lamps where from all info I am aware of or have been told, the halogen cycle takes place within the lamp at all stages of dimming where the filament is hot enough to project light. Also, the effects of lamp life on lamps under dimming has been well stated by me over the years so I won't repeat it but the effects of dimming on a 300 hour lamp is extending it exponentially beyond that at full voltage rating. Even a 5% change in the voltage applied to the lamp will etend it's lamp life by 60% for the time that lamp was on at 5%.

(Side note, not seeing much about trim settings on one's dimmers / pre-heat voltages applied to the lamps already in this discussion.)

Here is a similar tidbit about low voltage lamps which might be the source of confusion:
Low Voltage Dimming: Low Voltage halogen lamps should not be dimmed by more than 10% of their rated voltage since this will result in a reduction in life. Standard tungsten filament lamps (with no halogen filling), can be dimmed to zero volts, resulting in virtually endless life. However if low voltage tungsten halogen lamps are dimmed by more than 10%, the lamp will be operating at too low a temperature and the free halogens in the gas fill, will attack the cooler parts of the tungsten filament i.e. where enters the quartz or glass envelope. The wire at that point will then be eroded and eventually will fail. So if dimmed by 10% or more low voltage tungsten halogen lamps will not have an extended life but are unlikely even to reach their rated life. - Philips Website, Optical p1.

Also:
Osram offers landing and take-off lamps in a wide range of wattages. These lamps are designed to operate in series and will last on average for 1,000hours. Thanks to modern halogen technology, the lamps can be operated well below their current rating with no loss of service life.

And:
Operating Temperature = The following maximum and minimum temperatures are suggested for optimum life in tungsten halogen studio lamps. Operation outside these figures will not necessarily cause immediate failure but will affect life adversely to an increasing extent. Seal temperature - 450̊C max. Above this figure the sealing foil oxidizes at a rate increasing with temperature and is frequently the cause of short life due to seal temperature. (The point to which gas is injected into the globe.) Bulb/Globe - 250̊C to 800̊C - outside this range the halogen cycle becomes less efficient and blackening may occur. Temperatures above 1,200̊C will cause the bulb to soften. Pins - 350̊C maximum. Above this figure the plating on the pins may lose adhesion and the contact will deteriorate. Such deterioration may form local hot spots which rapidly worsen and may result in arcing and irreparable damage to both lamp and holder. Should signs of this be evident on removal of a failed lamp, it is important that a good contact is restored by replacing the lampholder before the next lamp is fitted. Otherwise the new lamp will rapidly fail in a similar manner. (Unknown source)

Series Operation = Life of a lamp can be severely reduced by using a series application because of the different resistances of the lamps used in the circuit. The applied voltage is not distributed evenly over all of the lamps in the series, so each lamp is operating at a slightly different voltage. This means embrittlement and the evaporation rate will not be equal, so some lamps could fail prematurely. It is recommended that lamps be selected for amperage and operated at a derated voltage for maximum reliability in series operations. (Unknown source)

Than:
Tungsten = Tungsten filaments change electrical energy to radiant energy. The light generated results from the filament being resistance heated to a temperature high enough to produce visible light. Filaments can not be operated in air see seal and vacuum. Tungsten is used for the filaments because of its low rate of evaporation at temperatures of incandescence and its high melting point 3,655̊K. There are grades of tungsten purity and different grain structures. Only the highest grade of an elongated grain structure guarantees maximum life and reliability during shock and vibration. Heat treatment of the tungsten filaments is one of the most critical factors in lamp manufacturing.. Proper heat treatment prevents filament sag, abnormal coil shorting or premature breakage. 
Tungsten Halogen Lamps = Halogen Lamps are tungsten fliament incandescent lamps filled with an inert gas (usually krypton or xenon to insulate the filament and decrease heat losses) to which a trace of halogen vapor (bromine) has been added. Tungsten vaporized from the filament wire is intercepted by the halogen gas before it reaches the wall of the bulb, and is returned to the filament. Therefore, the glass bulb stays clean and the light output remains constant over the entire life of the lamp. (p33, Sylvania Lamp & Ballast Product Catalog 2002)


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## David Ashton (Dec 11, 2007)

I pulled that off the GE site, however the halogen cycle is a function of temperature and the voltage of the lamp is not an issue.I am puzzled as to why you might think that the mechanics of the halogen cycle would change with voltage.


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## icewolf08 (Dec 11, 2007)

allthingstheatre said:


> I pulled that off the GE site, however the halogen cycle is a function of temperature and the voltage of the lamp is not an issue.I am puzzled as to why you might think that the mechanics of the halogen cycle would change with voltage.


If you are referring to Ship's mention of low voltage lamps, then I don't think what is meant is that the halogen cycle is affected by voltage. The halogen cycle is affected by heat, and low voltage lamps produce less heat than line voltage lamps, so if you dim them down they produce even less.


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## David Ashton (Dec 11, 2007)

The heat in a lamp has virtually no relation to voltage, it is a straight function of wattage, except for a tiny gain in the percentage of heat converted to light, and where does low voltage begin? a high voltage and low voltage lamp contain the same materials doing the identical physical and chemical reactions at the same temperature, a longer filament is the only essential difference.


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## JD (Dec 11, 2007)

Well, almost straight. It's actually a ratio between the wattage and the envelope size. That's why quartz bulbs are small, to get the surface temperature high.

One thing I have noticed is that enclosed quartz lamps (think par) are less likely to "cloud" over than open air quartz lamps. I suspect air convection cooling the envelope faster is the cause.


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## icewolf08 (Dec 11, 2007)

allthingstheatre said:


> The heat in a lamp has virtually no relation to voltage, it is a straight function of wattage, except for a tiny gain in the percentage of heat converted to light, and where does low voltage begin? a high voltage and low voltage lamp contain the same materials doing the identical physical and chemical reactions at the same temperature, a longer filament is the only essential difference.



Wattage is a function of voltage. If resistance is constant (which in theory it is for any given lamp) and the voltage changes, then the number of amps has to change. It's Ohm's Law, V/I=R (I=Amperes). Then if you take the volts and amps and plug into Watt's law W=VA then you have wattage changing based on voltage. Therefore if you say that temperature is a function of wattage it is also a function of voltage.

Higher voltage lamps have to have a higher resistance in order to output the same wattage as lower voltage lamps. Here is an example:
120W 120v lamp draws 1A - 1Ω resistance
120W 12v lamp draws 10A - 0.1Ω resistance​In theory, more resistance equals more heat. So in theory heat has more to do with the resistance of a lamp than the wattage.


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## Radman (Dec 11, 2007)

SteveB said:


> The Express has had one PS replaced, but it wasn't a heat issue. The Express also has no fans and I was told years ago there was no real reason to shut it down as long as it's on a good UPS (that was the advice from ETC). Our building power is fed underground so we don't see lightning hits either. The Emphasis is in a enclosed box with vents and a temperature sensor to activate cooling fans as needed. I do sometimes shut both down if there not used for more then a few days, such as over Christmas or in the summer. In general we use the system every 2-3 days, for a few days in a row, thus it's time effective to leave on so as to allow the RFU control without having to open up the console position (rear orchestra).
> 
> SB


Unless your power is underground all the way to the power plant, I wouldn't feel so safe. I worked in a theatre where the power was underground where it came to the building and probably stayed underground for a few miles, but eventually it comes up and hooks on to bigger branches of the distribution system. A tree fell on a line out in the country miles away and screwed up the dimmers and console for the whole first act of a show.


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## David Ashton (Dec 12, 2007)

icewolf08 said:


> Wattage is a function of voltage. If resistance is constant (which in theory it is for any given lamp) and the voltage changes, then the number of amps has to change. It's Ohm's Law, V/I=R (I=Amperes). Then if you take the volts and amps and plug into Watt's law W=VA then you have wattage changing based on voltage. Therefore if you say that temperature is a function of wattage it is also a function of voltage.
> Higher voltage lamps have to have a higher resistance in order to output the same wattage as lower voltage lamps. Here is an example:
> 120W 120v lamp draws 1A - 1Ω resistance
> 120W 12v lamp draws 10A - 0.1Ω resistance​In theory, more resistance equals more heat. So in theory heat has more to do with the resistance of a lamp than the wattage.


Sorry but totally absolutely wrong, power=heat=wattage, how you arrive at that wattage is irrelevant a 100 watt 240v lamp produces the same amount of heat as a 12v 100 watt lamp, namely 100 watts.


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## gafftaper (Dec 12, 2007)

I'm not an electricity wizard like some of you guys but I do vaguely remember being taught that resistance is not constant. As heat increases resistance increases. I found this on the internet:

"Resistance also depends on temperature, usually increasing as the temperature increases. For reasonably small changes in temperature, the change in resistivity, and therefore the change in resistance, is proportional to the temperature change. At low temperatures some materials, known as superconductors, have no resistance at all. Resistance in wires produces a loss of energy (usually in the form of heat), so materials with no resistance produce no energy loss when currents pass through them. "

The website also has a formula for calculating the temperature effect on resistance... which doesn't copy due to the font I guess.

I also found this site with a nifty little demo video that shows how as a wire is heated resistance drops and the battery powered lamp gets dimmer. Granted they are heating the line carrying power to the lamp and not the lamp itself. 

While this undermine's Alex's previous point, I'm pretty certain that the "all 100 watt lamps are the same temperature" theory is also wrong. When I teach my beginning students about Lumens and foot candles I start with house hold lamps. I show them that when looking at a household "light bulb", they should think about wattage only as a measure of how much energy is consumed, not as a measure of how bright it will be in their kitchen. I show them that if you go to a big hardware store that carries four brands of 100 Watt bulbs you will find they all have different lumen ratings. In this case I would also argue that wattage has very little to do with how hot a lamp is for the same reason. By using different conductive materials, gases, and envelops you could in theory construct a lamp that consumes a 100 watts of power but is barely warm to the touch (it might be 10' across and only last a few minutes but it's possible) or you could make one that can only produce 50 Foot Candles of light (charred bamboo filaments anyone?). The efficiency of the system that is inside the lamp is far more important than the wattage rating. I'm quite confident that four different household 100 watt bulbs would all have different operating temperatures.


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## David Ashton (Dec 12, 2007)

The resistance increase with temperature, by a factor of around 10 in a lamp, the only exception, if my recollections from school are correct, is carbon, which has a negative coefficient.


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## David Ashton (Dec 12, 2007)

> .
> So, that still brings us back to the preheating question. It isn't a question if if preheating will make you lamp last longer than the rated lamp life, it is a question of if preheating will make the lamp last longer than not preheating the lamp.
> Probably the ideal test would be to take two identical fixtures and lamps from the same lot, Preheat one at some low lever for some time and then turn both fixtures on to full in a 0 count. Let the fixtures burn for about 4 hours a day and repeat each day until one dies. I picked a 4 hour burn time because most theatres probably don't run their lamps for more than 4 hours a day. Running the lamps at full gives us optimum operating conditions, so we should get close to the rated lamp life.



This is not a valid replication of the theatre situation which is
pre-heat lights
turn lights off for 30- 45 minutes {while audience enters}
turn lights up to full for 4 hours{cue 1 go}
Even if pre-heating did work the break between pre-heat and show of at least half an hour completely negates any dubious benefit.


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## Grog12 (Dec 12, 2007)

allthingstheatre said:


> This is not a valid replication of the theatre situation which is
> pre-heat lights
> turn lights off for 30- 45 minutes {while audience enters}
> turn lights up to full for 4 hours{cue 1 go}
> Even if pre-heating did work the break between pre-heat and show of at least half an hour completely negates any dubious benefit.



And this isn't a valid situation. What you forget is a proper dimmer check.


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## icewolf08 (Dec 12, 2007)

allthingstheatre said:


> Sorry but totally absolutely wrong, power=heat=wattage, how you arrive at that wattage is irrelevant a 100 watt 240v lamp produces the same amount of heat as a 12v 100 watt lamp, namely 100 watts.


Power=heat=wattage is not true. Gaff is right, not all 100w lamps produce the same amount of heat. Power=heat=wattage would imply that all devices that draw the same wattage produce the same amount of heat, which also isn't true. I would happy run around with my IR thermometer to prove that, I just have to collect enough lamps of the same wattage, pretty easy to test though, and I will happily admit being wrong if I am, but I was taught that it is resistance that produces heat.

Also think about it this way, if there was no resistance there would be no heat. If there was no resistance there would be no light.



allthingstheatre said:


> This is not a valid replication of the theatre situation which is
> pre-heat lights
> turn lights off for 30- 45 minutes {while audience enters}
> turn lights up to full for 4 hours{cue 1 go}
> Even if pre-heating did work the break between pre-heat and show of at least half an hour completely negates any dubious benefit.


Hate to say it, but for most shows that I have worked on many lights are on as the audience comes in. Even so, the first cue of most shows (in theatre) is usually not a bump to full. In fact in most shows it is only at very few points in the show that lights make it to full. It is a fundamental of design, if you start at full you have nowhere to go from there, you can't get more exciting.

The test scenario that was suggested is based on ideal operating conditions for the fixtures. Very few shows would have a light on at full for the entire show, but that is how lamps are tested. In theory it should give as close to the rated lamp life as you can get when turning the lamps on and off. This because lamp life is determined by running the lamps at full until they die.

In theory the halogen cycle will start as soon as the filament is hot enough to start burning off tungsten. At this point it should be hot enough to break the tungsten-halide molecules to have the tungsten redeposited. You can think about it this way too. If a 12v lamp says that for best results you shouldn't run it at less than 80% on a dimmer then since 20% of US line voltage is 24v running that 120v lamp at 20% should be enough to get the tungsten cycle going. This may not have the cycle at it's most efficient, but it will be working none the less.


Keep in mind that this is all in theory, and I would be happy to be proven wrong, but just saying I am wrong because what you say is right doesn't make sense. I have offered plenty of reasoning for my thoughts here, and I would happily call some of my old professors who would happily help answer the questions here.


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## JD (Dec 12, 2007)

Some scientific principles apply here; Input >> Output, Input = Output. (Sorry, no text arrows) Basically, whatever you put into something, you are going to get as output in some form. In this case, our input is electricity, and we will measure that in watts. (volts times amps) Our known outputs are Heat, Light, Magnetism and maybe a little of something else, who knows! So, the question is- How much of each? 98% heat, 1.5% light, .5% Magnetism? If so, our bulb has an light efficiency of 1.5% 

It is putting out other stuff, but we only really want light. If all lamps were the same efficiency,and everything else was constant, then all bulbs of the same wattage would produce the same amount of heat. But, they aren't. If a lamp is 2% efficient, it will produce that much less heat. Mind you, the numbers I picked are arbitrary, but I do know that efficiency is a variable. If efficiency is variable, then heat output from lights of the same wattage are variable. If not, then we had better dig up Einstein and ask him what went wrong


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## derekleffew (Dec 12, 2007)

Alex has inspired me to conduct an experiment with my own IR Thermometer. I measured the surface temp. of the envelope of a 500watt EHD lamp at various voltages. Results are attached below. I have no idea what, if anything it proves.

Until it's proved or explained to me that what I'm doing is actually detrimental to my lamps, I will continue to do as I've always done as Master Elect/Board Op. on long running shows:

Come in for show call. All dimmers to 10-25% over at least 5 minutes to: a) gently warm the filament and b) allow for me onstage to check for burnouts and melted color media. [We ALL agree that bring a lamp up slowly is less likely to cause a failure than bumping it to full, Correct?]Then, either auto or RFU or another person at the board (although I prefer doing it auto once I know the focus, I find it more efficient) bring each dimmer to Full (manually: <ch1 @ FL *> or auto (effect): "on a 2 second fade.")

If a lamp has failed and gone unnoticed during the previous show, I'll see it during the preheat period. If a lamp fails during the dimmer/focus check, I'll see it.

I have discovered, through experience, since 1981 when I first started running memory consoles, that if I preheat lamps at the beginning of the day, I change fewer lamps than if I come in and start at <Dimmer 1 @ FL *>. Note I only do this once we enter the "show run" phase, not during hangs, focuses, or techs. We always seem to lose more lamps then, possibly from fixtures being moved about, possibly as a way of "weeding out" lamps near the end of their life.

An HPL575 is what, about $20 US, and has a rated life of 300 hours. That's 6.7¢/hour, worst case scenario, and we know that running the lamp at 90% extends life something like 400% (not exact, old "rule of thumb"). [We ALL agree that we generally get more than the rated life out of our lamps in the theatre, correct?] It's not the cost of the lamp or its life or the cost of power I'm worried about, it's the labor cost to replace it and the detrimental effect it will have if it blows during a show.

This has been one of the best discussions (arguments) you've ever posed, Gafftaper. Time to start another, as I feel this horse is dead. (Though its cause of death is still undetermined, and likely to be so for a long while.)

(JD/steveterry/BillESC/Logos--You may remember the "urban myth" that circulated in the 1970s upon the introduction of Q/I (T/H) lamps. It was said they wouldn't hold up if bumped to full, and therefore were inappropriate for rock&roll. I don't think we need _Mythbusters_ to disprove that.)


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## gafftapegreenia (Dec 12, 2007)

Derek, what is that lamp base from?


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## derekleffew (Dec 12, 2007)

gafftapegreenia said:


> Derek, what is that lamp base from?


You're the next generation of "Theatre Lighting Historian", you tell me! The fixture IS listed in the _Photometrics Handbook_, many times. Nobody else help him, okay? And it's a "Lamp Cap." (Complete assembly.) You can't see the lamp base (or socket) in the picture.


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## soundman (Dec 12, 2007)

not helping


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## avkid (Dec 12, 2007)

Uh oh Derek, you're setting a bad example for the younger ones.
That cable coming out of your switchbox looks like SJTW, and the strain relief is a simple clamp.


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## derekleffew (Dec 12, 2007)

Thank you, Philip, for noticing. The cable IS in fact SJTW and it IS a 19¢ "Romex Clamp." It was built before you were born, and I have used it as a "Booth Running Light Dimmer" many, many times. I dare say IT has run more shows than you have.

"Do as I say, not as I do." Or, if you prefer, "Because I'm your mother, that's why."


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## avkid (Dec 12, 2007)

derekleffew said:


> "Do as I say, not as I do." Or, if you prefer, "Because I'm your mother, that's why."


I prefer the former.


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## David Ashton (Dec 12, 2007)

Power =heat= wattage is absolutely true unless you have discovered a new branch of physics Newtonian physics says that energy cannot be destroyed only turned from one form to another e.g.electricity - heat -light.
If one has to invent a new branch of physics to justify pre-heating then please feel free.


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## gafftaper (Dec 12, 2007)

allthingstheatre said:


> Power =heat= wattage is absolutely true unless you have discovered a new branch of physics Newtonian physics says that energy cannot be destroyed only turned from one form to another e.g.electricity - heat -light. If one has to invent a new branch of physics to justify pre-heating then please feel free.



WHAT? 

Your are 100% correct about Newton... the electricity is being converted to light AND heat. The design of the lamp dramatically alters how much becomes heat and how much becomes light. A very efficient design will produce more light and less heat. If I go to the hardware store and buy two 100 watt lamps with different lumen ratings clearly they must run a different temperatures because as you said the energy is either being converted to heat or light. If they have different light outputs then they MUST also have different heat outputs to compensate. 

If power=heat=watts then explain this to me: 
A 1000 watt FFN VNS PAR64 lamp puts out 11,000 lumens
A 1000 watt BTR lamp puts out 20,500 lumens

The BTR is far more efficient, converting more of it's energy to light than the FFN. They both consume 1000 watts of power. Where does the rest of the energy go? It turns to heat, but at different rates due to the different efficiencies of the two lamps. Furthermore, the temperature of the lamps will be vastly different due to the difference in envelope size to dissipate that heat.


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## derekleffew (Dec 12, 2007)

Gafftapegreenia has either given up or is trying to cheat by emailing me. Either way, his answer is below.

I think I said before that I "liberated" this fixture because the students kept hanging it upside down. The label on one side of the lens tube was affixed upside down at the factory. So much for quality control in 1979!

Until the SourceFour™ in 1994, this was my favorite line of ERSs. I still prefer its lamp alignment over all others: completely tool-less, every lamp change requires a peak-cosine adjustment, and the joystick is the simplest I've ever used. Strange that the _Photometrics Handbook_ doesn't have the entire line of these--I wish I had the original cut sheets to send to Mr. Mumm.


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## David Ashton (Dec 12, 2007)

It is so simple I can't understand the problem
A 1000 watt lamp consumes that amount of power which it converts to heat this heat is converted to light.
There is a trade off between all the design factors in a lamp such as robustness life, output levels, colour temperature etc.
So you choose the optimum lamp for your application e.g. very bright for very few hours or very dim for a hundred years or some point in between.
Whichever end of this range you choose you are still using 1000 watts and the 
efficiency is your choice, to suit your needs. 
Because the light conversion is very low practically both lamps will produce the same amount of heat.

It is simply a question of how much heat is generating light, which is a problem in this thread.


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## gafftapegreenia (Dec 12, 2007)

Gah, Strand-Century, I'm not too good with all the ERS's from that vintage. I don't come into contact with Strand's much.


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## icewolf08 (Dec 12, 2007)

allthingstheatre said:


> It is so simple I can't understand the problem
> A 1000 watt lamp consumes that amount of power which it converts to heat this heat is converted to light.
> There is a trade off between all the design factors in a lamp such as robustness life, output levels, colour temperature etc.
> So you choose the optimum lamp for your application e.g. very bright for very few hours or very dim for a hundred years or some point in between.
> ...



Heat cannot be converted to anything, let alone light. That is the law of entropy and chaos theory. Heat, in and of itself, cannot do any work. The only thing that heat can do is escape and eventually grow cool. Heat is a product of work. To get heat you need to use energy, heat itself has no potential energy. Heat can be transfered between bodies, but only until a thermal equilibrium is reached.

On the other hand, light is capable of doing work. For one thing, light can be converted to heat. Light can also be converted to electricity using photovoltaic cells.

When you turn on a light, the resistance of the filament causes it to glow, emitting light. The resistance of the filament also creates heat. The heat does not create the light, the resistance of the filament creates the light.

Also think on the black body radiator model, it says that to have a warmer color temp the actual heat produced is lower. Therefore an HPL750 should be physically hotter than an HPL750X which has a warmer color temp.

You still have not backed up anything you have said with either scientific data, or real world experimental data. So, if I have to, I will go in to work tomorrow and shoot the temperatures of the two different 300w lamps that we use for house light lamps and I will shoot the temps of an HX-755 (a 750w long life lamp) and an HPL750. I don't think I have any low voltage lamps that I can test. I still have to work out a test procedure though because my IR thermometer I don't think can measure high enough. I have a digital temperature probe that has a higher max, but I don't know if I can do what I need to with it.

As I have said, I am happy to be proven wrong, but so far no one has offered any proof.

Try looking at it this way, there are many people who teach preheating, there are many who preach it, and there are many who do it. If there was no good reason to do it why would so many people think that it is a good thing. Every stereotype is based on fact, the fact may not be a fact any more, but it was at some point.


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## ship (Dec 13, 2007)

Ah' them Lekos... nice, want one. Yep, grew up with them also - back in high school and to some extent in college.

Still one thing about pre-heating that has not been mentioned is the pre-heat voltage many types of dimmers and pre-sets apply to the lamps as benefit in both lack of cold start and quicker lamp to full times. Most dimmers I have worked on over the years do have a trim setting where by you can adjust the minimum voltage applied to the lamps - normally like 13v or adjust it down for say never applying full voltage to the lamps in extending lamp life. Can adjust the dimmers for this setting and a common problem in setting the dimmer trim. Since more modern dimmers I realize this say 0-85% actual dimmer ratio was a base of what was set between warming current for the lamps and what was full applied to them.

A few styles of pre-show lamp check have been mentioned - this lamp to lamp or low dimmer setting with all on and searching for the one that is out, both work adiquate when brought up slow given cold start or fine when brought up after a short period of time with simply dimmers on.

It is often noted, short of pre-warming the lamps, bringing them up slow is necessary - this especially with low voltage lamps I would add.

Valid point the question of doing the pre-show warming of the lamps some given say that warming current and time to cool down before the show starts in doing any good at all. Perhaps such a concept is left over from the days before warming currents that I am familiar with and will zap you to some extent if not aware of such a thing. Than again, if a lamp is only warmed, perhaps before the show it is not such a bad thing to before the show induce a bit more to it so as to ready / refreshen that lamp before its important use. This by way of readying the lamp for use or simply attempting to blow it out if it is going to go before the show rather than during the show.

Still, I would think tradition or not, doing what is common to do is not a bad thing overall benefit or not. Extra chance if nothing else that lamp if ready to go will go before rather than during the show.

Good discussion, all sides to some extent have valid points and good to learn from. Much further discussion and study on both sides no doubt will end in a much better understanding of what to do and how it all works. Not a bad thing.


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## David Ashton (Jan 16, 2010)

QUOTE FROM iCEWOLF.
'Heat cannot be converted to anything, let alone light. That is the law of entropy and chaos theory. Heat, in and of itself, cannot do any work. The only thing that heat can do is escape and eventually grow cool. Heat is a product of work. To get heat you need to use energy, heat itself has no potential energy. Heat can be transfered between bodies, but only until a thermal equilibrium is reached.

On the other hand, light is capable of doing work. For one thing, light can be converted to heat. Light can also be converted to electricity using photovoltaic cells.

When you turn on a light, the resistance of the filament causes it to glow, emitting light. The resistance of the filament also creates heat. The heat does not create the light, the resistance of the filament creates the light.

ABSOLUTELY WRONG, of course heat can be converted to light or electricity or work. the resistance of the filament does not cause it to glow, I have boxes of resistors none of which are glowing, it is only when a filament is hot that it produces light.
If some poor physics student comes across Icewolfs theory and uses it in class, he or she will be seriously embarrassed.


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## icewolf08 (Jan 17, 2010)

David Ashton said:


> ABSOLUTELY WRONG, of course heat can be converted to light or electricity or work. the resistance of the filament does not cause it to glow, I have boxes of resistors none of which are glowing, it is only when a filament is hot that it produces light.
> If some poor physics student comes across Icewolfs theory and uses it in class, he or she will be seriously embarrassed.



Surfing though old threads I see....

Actually, the heat does not do any work. The electricity does the work. Heat is a byproduct. I will admit that I am wrong in saying heat does not cause the filament to glow, but the heat is not doing the work. The electricity meets resistance in the filament, the filament heats up and glows.

To get really technical about it, passing current through the filament causes electrons in the atoms of the metal to change energy states. When an electron drops from one shell to another it emits a photon. Get a lot of atoms excited and they emit lots of photons, thus you get light. At the same time, as with any resistor you generate heat as a byproduct.

NOw, it has been a long time since i have taken a physics course, but I don't think that this has changed.


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## Les (Jan 17, 2010)

icewolf08 said:


> Get a lot of atoms excited and they emit lots of photons



Sounds like my family gatherings...


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## David Ashton (Jan 17, 2010)

The First Law basically says that energy or matter can neither be created nor destroyed. In terms of the machine, this meant that the total energy output (work by the machine) is equal to the heat supplied. In other words, the change in the internal energy of a closed system is equal to the heat added to the system minus the work done by the system. Because the system operates in the real world, some energy always escapes into the outside world, thus leading to both inefficiency and the Second Law, which was generated to cover the so-called flaw in the First Law. 
This is Newtons first law of thermodynamics, and unlike Icewolfs law of thermodynamics, heat can absolutely do work, it is the heat measured in Watts which heats the filament and produces the light, no semantics can get around that absolute fact.


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## MillburyAuditorium (Jan 17, 2010)

I run everything at 30 for a while, while getting ready, then do a s sub and lamp check.


JD said:


> Ahh! The preheat issue again!
> 
> Also, any visible output means that tungsten is vaporizing off of the filament,



So that's what makes a beam of light visible with no fog or haze? Because at a band concert last week I could see all the beams of lights from our Colortran Ellipsoidals' by the end of the night.
It gets REALLY hot in there during concerts.


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## Les (Jan 17, 2010)

MillburyAuditorium said:


> I run everything at 30 for a while, while getting ready, then do a s sub and lamp check.
> 
> 
> 
> ...



Actually, what you're seeing isn't vaporized filament, but rather a phenomenon we refer to as dust.


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## photoatdv (Jan 17, 2010)

The vaporized Tungsten will stay within the lamp envelope (unless it goes boom of course)...


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## xander (Jan 17, 2010)

I don't think that the argument between Icewolf and David Ashton is going to be resolved by silly old me. I have a feeling it will at the very least take a post from someone that they mutually respect and deem an expert in the field. All of that said, I do want to make some statements of my own. I feel that there is a bit of a semantic problem. 


David Ashton said:


> The First Law basically says that energy or matter can neither be created nor destroyed. In terms of the machine, this meant that the total energy output (work by the machine) is equal to the heat supplied. In other words, the change in the internal energy of a closed system is equal to the heat added to the system minus the work done by the system. Because the system operates in the real world, some energy always escapes into the outside world, thus leading to both inefficiency and the Second Law, which was generated to cover the so-called flaw in the First Law.



This statement, that David Ashton so blatantly plagiarized from this website Three Laws of Thermodynamics - Physics Planet .com 
paragraph 5, I think is using the word heat to describe the internal energy of a system. It does not mean the kind of heat we are use to in everyday life. I.e. It does not follow that if you pointed a hair dryer at a motor, it would start turning.
Heat, work, and energy are all really the same thing in physics terms. They are all measured in Joules, or Newton-meters.
This leads to my second point,

David Ashton said:


> This is Newtons first law of thermodynamics, and unlike Icewolfs law of thermodynamics, heat can absolutely do work,* it is the heat measured in Watts* which heats the filament and produces the light, no semantics can get around that absolute fact.


Heat is most absolutely not measured in watts. Like I said, heat is measured in Joules. Watts is the unit of measure of power, or a Joule per second. While related, you are completely disregarding time.

It is true that while electricity is flowing through the filament it is the resistance of the, in most cases we are talking about tungsten, that causes the filament to produce radiation. The wavelength of this radiation starts out fairly large and all that we (humans) perceive is heat. As more and more energy is pumped into the filament the radiation that is produced becomes of a higher and higher frequency and we feel it getting hotter and hotter. Up to a certain point, all of the radiation produced in infrared. After that point, the frequency of the radiation reaches the visible portion of the electromagnetic spectrum, which we refer to as light. 
In actuality it is all the same thing, heat and light, we just refer to the heat as a waste, or byproduct, because it is the light that we are after.

As for your resistors, there are many different reasons why they don't light up. I feel silly even having to explain this, but one is because your resistors aren't in a vacuum (or gas such as halogen) envelop. The heat produced by the resistance will deteriorate the material long before they get hot enough to glow.

Please feel free to add any constructive criticism of how I described the process, but at least try to use proper definitions that can be found in any dictionary.

-Tim


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## David Ashton (Jan 17, 2010)

quote"Heat is most absolutely not measured in watts."Oh yes it is ,it can be measured in Joules in the imperial system or horsepower, this is what seems to be totally not understood,Heat = work =electrical power =light =radio power. Not only are they interchangeable but the units they are measured in are also interchangeable.This is not my theory blame Mr Newton.
So many here work in schools, just wander over to the Physics dept and get an opinion.


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## xander (Jan 17, 2010)

I told you my post wasn't going to solve anything, but can I just ask that you please look up the term "watt" in a dictionary, any dictionary. It'll say something like, "the absolute meter-kilogram-second unit of power equal to the work done at the rate of one joule per second or to the power produced by a current of one ampere across a potential difference of one volt : 1⁄746 horsepower" (Merriam-Webster Online Dictionary). The important part being "at the rate of one joule per second". You cannot say that Watt=Joule *and* Watt=Joule/Second. Like I said before, 
*WATT IS A UNIT OF POWER, NOT ENERGY*

I've totally forgotten what this thread was originally about...
-Tim


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## David Ashton (Jan 17, 2010)

I admit to a slight slip there I should have said Joules = watts/time, a bit different from the new Icewolfian physics where heat does not exist.We all tend to shorten terms to make life easier.


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## xander (Jan 17, 2010)

David Ashton said:


> I admit to a slight slip there I should have said Joules = watts/time,


While even this is wrong, it is Watts = Joules / Seconds OR Joules = Watts x Seconds, I understand what you are saying. 

David Ashton said:


> a bit different from the new Icewolfian physics where heat does not exist.We all tend to shorten terms to make life easier.


Icewolf never said that, or anything of the sort. What he said is simply that heat has no potential energy. That is not synonymous with not existing. It is not even synonymous to not having energy. There are 3 types of energy; kinetic, potential, and the rest, i.e. thermal, nuclear, solar, etc. Icewolf is simply stating that heat does not have any potential energy, but it does have thermal energy.

Ceding that I am right about the definition of "watt" still doesn't get you out of what you are saying, though. You stated that the heat makes a filament give off light. Let me try this again:
Let us assume our lamp is a closed system, in thermal equilibrium. When we apply a voltage (say 120v or 240v) across the two leads this creates an energy potential. When current is applied, we can say that energy (in the form of electrical energy) is being added to our closed system (the lamp). What happens to our added energy? If there was zero resistance in the filament (and wires of the system) then all of the energy would go straight through the filament and do it's business elsewhere, (like blow the fuse/circuit breaker), thus leaving the net energy of our system unchanged. However, like any system in the real world, there is resistance, in our case in the filament. When the energy reaches this resistance, it is converted (like I went through in my other post) to other form(s) of energy. This is the heat and light that we perceive. This electrical energy is added to the system and the radiation, both infrared (the heat we feel) and visible (the light we see) is given off so that the net energy of the system remains zero.

Now, hopefully, I will stop hijacking this thread 
-Tim


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## MSLD (Jan 17, 2010)

I don't know if this was already mentioned. BUT!! how long before the star of the show should you do the preheat as to not let them cool down too quickly?


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## David Ashton (Jan 17, 2010)

"This electrical energy is added to the system and the radiation, both infrared (the heat we feel) and visible (the light we see) is given off so that the net energy of the system remains zero."

I'm so sorry, I have slipped into a parallel universe with different laws of physics.Please carry on.


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## xander (Jan 18, 2010)

David Ashton said:


> I'm so sorry, I have slipped into a parallel universe with different laws of physics.Please carry on.



That is meaningless. I am putting forth the effort and trying to get you to understand by going step by step and explaining. If you believe that something I have said is incorrect, then point it out and explain why it is incorrect. Simply stating, "I am right and you are wrong, ninner ninner ninner" is not an argument.

-Tim


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## Morpheus (Jan 18, 2010)

xander said:


> David Ashton said:
> 
> 
> > I'm so sorry, I have slipped into a parallel universe with different laws of physics.Please carry on.
> ...



Input = Output...

So, David, apology accepted. We'll wait for your return in the real world.


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## MaddieNevins (Jan 18, 2010)

Preheating lamps before a show is a very good idea. Whenever I design a show I make sure I program a cue that is set for dimmer/channel check. It's normally like cue .5, and has all the instuments up at about 25%. This allows the lamps to warm up, and also allows the lighting crew to check and make sure there are no burned out gels or instruments before each show.


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## icewolf08 (Jan 18, 2010)

I think there is a big difference between preheating before a show and preheating a unit before a cue. I don't remember who pointed it out earlier in this thread, but preheating before the show will not really help anything out aside from electricians doing a lamp check. Generally, I am coming in to the theatre an hour to an hour and-a-half before the half hour to do my channel check. If I warm the lights (which I do), by the time I get through 200+ channels in the show, that last light has cooled off again. The lamps just don't have enough thermal mass to stay warm.

So why do I warm the lights before my channel check? Probably because that is what I was taught to do in school and that is what a lot of people that I know do. Odds are it isn't going to really hurt anything, but it probably doesn't really help either (aside from allowing me to do a broadway check)

Now, preheating a fixture in the cue before it needs to come up can help you out up the dimmer curve. It can be especially useful if you have cues that bump larger fixtures up and on so that you see more of a bump than a fade. Have you ever bumped a cold 2K or 5K fresnel to full? It looks more like a fade because of the time it takes to warm up the filament. However, if you run the channel at 3-is percent then it won't give off much, if any, light but it will bump on much faster in the next cue. This works for many situations where you just need to be a little ahead on the dimmer curve to get a smooth fade. Some people even build this into their dimmer profiles for a show so that when you take a channel to zero it actually sits around 3%.


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## photoatdv (Jan 18, 2010)

And why you should unplug lights before relamping...


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## philhaney (Jan 18, 2010)

photoatdv said:


> And why you should unplug lights before relamping...



Never force an interlock.

Always treat a firearm as if it were loaded.

Never trust (or believe) that your dimmers are off.

SAFETY FIRST!


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## Anvilx (Jan 18, 2010)

philhaney said:


> Never force an interlock.
> 
> Always treat a firearm as if it were loaded.
> 
> ...



Always Respect Gravity.


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## JD (Jan 19, 2010)

Wow! 99 posts on preheats! Well, here is 2 more cents. If I load a show in during a cold winter day for a one nighter, then I do a long preheat. It helps dry the condensation out of the fixtures. If the show is a long run, then not-so-much. I have my dimmers trimmed at about 2% so as long as rack power is on there is some heating. I usually do not power my racks unless I am in the building. (Keep in mind, I do mainly one nighters.) With regard to fixed locations, it can waste a ton of energy. At 5% or less, you are not hurting the lamps as the filaments are not at a temperature that is hot enough to boil off tungsten, you are however using up a lot of power. I know many leave things powered 24/7 and if that is the case then 0% is much better for many reasons. Power off is still best because you eliminate potential surge damage while the equipment is not in use.


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