Preheating Conventionals?

gafftaper

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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?
 

zac850

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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?
 

icewolf08

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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.
 

soundlight

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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.
 

SteveB

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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
 

icewolf08

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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.
 

JD

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North Wales PA
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!
 

Grog12

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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.
 

DarSax

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

avkid

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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.
 

Footer

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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).
 

SteveB

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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
 

fosstech

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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. ;)
 

Pie4Weebl

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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.
 

gafftaper

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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.
 

David Ashton

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perth W Australia
"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.
 

SteveB

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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
 

David Ashton

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perth W Australia
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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