Film-Tech Forum ARCHIVE: Leaving the exciter on

This is topic Leaving the exciter on in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=002931

Posted by Ken Lackner (Member # 1002) on 01-04-2002, 08:05 PM:

For many types of bulbs, it is better to leave them on for longer than necessary rather than shut them on and off constantly. Less wear and tear. Is this true for exciter lamps? I am talking about actual white bulbs, not the LED's. Is there any reason I should not leave my exciters on all day and only turn them off when I shut down at night?

Posted by Bob Healey (Member # 1003) on 01-04-2002, 08:54 PM:

We run changeovers, and our exciter supply can only drive one lamp at a time, so everytime we swap projectors, one bulb is switched off, the other on. This is done internally in the power supply (Kelmar). In the year and 1/2 I've been there, haven't seen one changed, but then again, there are only about 24 operating hours/week there. No one else can remember the last time one was changed either.

Posted by Scott Norwood (Member # 30) on 01-04-2002, 09:46 PM:

Interesting question.

Personally, I prefer to leave exciter lamps on whenever the theatre is open. My reasoning for this is failures usually occur when the lamps are first powered on and that I would rather not have one burn out right at show start or at a changeover. In practice, though, failures are pretty rare.

I don't like exciter-lamp changeover systems, either, since they have the additional problem of causing a second or so of silence at every c/o while the second lamp comes up to full brightness. I find this very noticeable and distracting (especially when combined with a 'pop' at every c/o, which seems to happen in way too many older theatres).

I'd be interested to hear if anyone has actually done any testing to prove one way or the other whether exciter life is reduced by repeated power-cycles during the course of a day.

Posted by John Walsh (Member # 168) on 01-04-2002, 11:35 PM:

Both the "silence at c/o" and the wear on bulbs can be reduced by still powering the bulbs, but reducing the voltage to about 10% of normal for the nonoperating projector. This is usually a simple modification; soldering a power resistor across relay contacts on the automation. It will vary of course if you have c/o's or single projector. You may have to experiment a bit to get the right voltage (just a little less than what would make the filament start glowing.)

This is a common trick also used by every stage lighing equipment. It allows the filament to stay warm, but dark. Since the filament is warm, it will come on quicker; scenes may require quick on. That same idea can be used for c/o's; the exciter supply may have to be adjusted a little higher to supply both the operating proj bulb and the 10% "not running" bulb.

Posted by Mark Gulbrandsen (Member # 72) on 01-06-2002, 09:38 AM:

Warming the filaments on stages is quite common and is a necessity with some really large lamps(2kw and up incandescent). All modern dimmer racks, or packs are now computer based meaning that each rack or pack has its own processor unit. This allows great flexibility and among the hundred or so adjustable software based things allows one to set minimum and maximum voltage output levels for each dimmer, individually, or as a whole.
As for exciters, I agree with installing a resistor across the relay to keep the lamp at about 10 to 15% of voltage in standby. Leaving them on all the time will allow vaporized tungsten to deposit on the glass inside the lamp, darkining it, and throwing calibration levels off. Exciter lamps do have an hour rating too like an xenon lamp, and should be taken into account in normal weekly booth maintainance. Better yet, get rid of the dang things and modernize!
Mark @ GTS

Posted by Jeff Stricker (Member # 224) on 01-06-2002, 10:50 AM:

Mark's reply brings to mind radio transmitters I have worked on.
Transmitting tubes are turned on using a step-start circuit. When the
filament is turned on, there is a dropping resistor in series
with the filament to allow warm up to approximately 60% of
normal operating voltage, then a timer actuates a relay which
shorts out the resistor and normal filament voltage is
applied to the tube. This greatly improves tube life in
transmitters that are only used for a portion of a 24 hour period.

Many years ago I worked at a small 250 watt AM station. We were
on the air from 6 AM to 10:30 PM. However, we found out very
quickly that we had less tube failures (this was 100% tube transmitter - 1946 vintage!) if we left the filaments on all night after sign off. If there was a catastrophic tube failure, it would occur when the filaments were first turned on by the morning guy...the tx was remote controlled and located 2 miles away from the studio, and a pain in the butt to work on in the early AM!!

Posted by Ray Derrick (Member # 1001) on 01-11-2002, 06:26 PM:

In fact, for long term reliability it is better to leave your sound rack on all the time rather than turning it off every night. It is the constant heating up and cooling down (causing expansion and contraction of physical materials) that does the most damage to electronic components. Voltage spikes at switch on is the other main factor.

As Jeff has indicated, this is well known in the broadcast and televison industries where over half a century of experience has proven that leaving equipment permanently powered on results in the least failures by a huge margin. Any small increase in the power bill is greatly offset by the reduced cost of repairs and replacements.

------------------
Ray Derrick
President
Panalogic Corporation Pty Limited
44 Carrington Road
Castle Hill NSW 2154 Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

Posted by Ken Lackner (Member # 1002) on 01-11-2002, 08:44 PM:

Ray,

So do you believe that leaving the equipment on should include the actual exciter bulb as well, or do is the heat buildup just as damaging as turning it on and off?

Posted by Dave Macaulay (Member # 813) on 01-11-2002, 09:42 PM:

I have 2 exceptions to the "leave it on is best" rule - things with motors running and lamps.
Motors just wear out bearings, and lamps just burn out. There are theories that turning an incandescent lamp on is worth a half hour of life, but for overnight they should be off. As already stated, the exciter lamp has a rated life and the light level drops as it ages. They should be routinely replaced at the rated life, not just when they burn out!

Projection equipment generally has no continuously running motors except fans. Ignoring for a moment that fans themselves have motors, units like amplifiers and CP500s that have cooling fans are a special case. It IS better electronically to leave them on but the fan will cause dust and dirt to build up all the time. I've seen amps and processors fail from overheating just because they were full of dust. The "good" of leaving them on is outweighed by the "bad" of sucking dirt in all night long.
If you have a dust free booth (hah!) or routinely open and clean the amps etc then leave em on. (you should have scheduled dust removal!)
High reactance rectifiers should be off at night. Nothing in it except the control transformer and fan is powered and they will get filled with dust and overheat too. Switchers are like amps, it is a tradeoff between stress and dust - but considering the power available to one - and how much smoke it could make overnight if it went really crazy - I would want them off.
The exhaust fan should be off. There is no reason to suck dust onto the mirror and lamp all night. (only exception is hot/wet climates where backdraft at night can cause condensation and really nasty rusting inside the lamphouse)

Posted by John Walsh (Member # 168) on 01-11-2002, 11:15 PM:

I don't think Ray meant leaving the exhaust fans on... just the sound equipment.

In one place I worked, they left the sound equipment on, and had very few problems. But I've worked in places that didn't, and also had vew problems.

In places that leave stuff on, I'd suggest the operators there make a special effort to change the HVAC filters often.

Posted by Ray Derrick (Member # 1001) on 01-12-2002, 02:51 AM:

Firstly I am not suggesting everyone should suddenly start leaving their sound racks on. I was simply stating the facts about electronic reliability.

Dust can be a consideration, however in a clean air-conditioned work environment, dust build-up should be minimal. Also many of the popular modern amplifiers have fans that only come on the when the internal temperature reaches a certain level, so they should not come on at all at night when there is no audio.

Obviously the decision to leave your sound gear on depends on your operating hours and many other factors. For example if you only show one session a day the increase in your power bill would probably outweigh any benefit. However for a cinema complex that runs from 10am until midnight, it may well be worth considering.

And no Ken, I was not suggesting leaving the exciter on all night - lamps are a different kettle of fish. Mark's suggestion of running it at 10% of normal when it is not in use, is a good one, but turn it off when you go home.

------------------
Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

Posted by William Bunch (Member # 1040) on 01-12-2002, 03:14 AM:

In our theaters we only have one showing on weeknights and two or three on the weekends. We always power down overnight. This is because of the dust problem. Our buildings (being military issue) are not always antiseptic. That and the base Fire Marshall says to.

Our sound racks will stay on for the whole evening no matter how many performances probably becase the non-sync system is on the same breaker.

Mark brings up a good point about the inside of the glass envelope being deposited with tungsten. But the main issue is filament sag. Whenever I do a Dolbly checkup on our sound opticals the first thing I check for is filament sag which can alter the output considerably. I would think that this sag would be proportional to the amount of total time that the lamp is operated.

I have nevr changed an eciter lamp because it was burned out. Only because it was dark, the adhesive base had let go throwing the lamp out of alignment or that the filament was sagging out of specs.

I doubt that mono equiped theaters would have to worry much.

Bill Bunch
Misawa, Japan

Posted by Ray Derrick (Member # 1001) on 01-12-2002, 04:23 AM:

William

How come the US military are still using exciter lamps? I though you guys were supposed to be at the leading edge of technology.

------------------
Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

Posted by John Walsh (Member # 168) on 01-12-2002, 10:10 AM:

For many things, the US military is on the leading edge of "low bidder!"

Posted by Mark Gulbrandsen (Member # 72) on 01-12-2002, 11:18 AM:

Willian said "the first thing I check for is filament sag"
Filament sag can also cause the loss of the very top end of the response curve as well. Having the exciter dead on with the actual slit in the slit lens is very important, especially with narrow slit lenses. Of course this is just another of the many reasons for installing reverse scan pickups...........

Indeed when I worked in broadcast television back in the late 70's we never did shut stuff down except to either work on it or move it. The only thing that was ever turned off were the beam switches for the studio cameras when they were not being used. Once a week we pulled maintainance on the TTU-100 transmitter and of course it was shut down for that for 6 hours every Sunday night. I never quite got used to having 18kv at 16 amps capacity flowing around me. That is the best job to hold to learn great respect for high voltage!
Mark @ GTS

Posted by William Bunch (Member # 1040) on 01-12-2002, 08:46 PM:

My company, ARMY, AIR FORCE EXCHANGE SERVICE (AAFES) kinda implies that we are part of the military. We sare in name only. We are actually a self sustained unit that provides products and services to the men and women in uniform. One of those services is motion pictures. You can read about us at http://www.aafes.com/pa/default.asp

One of the reasons we are still using much older equipment is that just like the mom and pops back home we have to pay our own way. We receive no taxpayer or military funds. All our investments must come out of our operating profits. Another reason is that with good machines like the Simplex and a competent staff it really is not necessary to change much. If it ain't broke, don't fix it. We do manage to keep with the times by upgrading optics and audio wherever possible.

The Navy also has a similar system on their side of the house.

Bill Bunch
Misawa, Japan
Army, Air Force Exchange Service

Posted by Tom Fermanian (Member # 1094) on 01-12-2002, 09:50 PM:

Bill,
Well kept "antiques" such as XLs if well kept are superior to a majority of the new projection equipement available today, the "grandchildren" of XLs aren't what the grandpas where!In one of our cinemas, Xls premiered in 1951, both machines where divided when the theatre became a twin in 1970, with proper upkeep,changing Spocket,Shoes, pads etc. one or two non-metal gears changed, we only had to have the intermitants rebuilt once each.
Proper sound optics where done a few years ago (in SH 1000s), changed to Kelmar Red Led, both projectors are running fine.If you can afford, change to this type, light much steadier, if optics are kept clean, almost no change in Dolby Tone levels during monthly sound level checks, this achieved by using newer optics & led's as compared to tungsten.
Tom

------------------

Posted by Tom Fermanian (Member # 1094) on 01-12-2002, 09:52 PM:

PS, Almost forgot, all our cinemas soundheads are transfered to LEDs, we leave LED's on during all operating hours of theatres. Tom

------------------

Posted by Ken Lackner (Member # 1002) on 01-13-2002, 12:58 AM:

My last theatre which is only 2 years old now, has reverse scan LEDs and they are on all day. I don't think there's any harm either way with LED's. But from the posts here, it looks as if I was wrong about the exciter bulbs. I guess it's better to turn them off when not in use rather than keep 'em on all day.

Posted by William Bunch (Member # 1040) on 01-13-2002, 06:35 AM:

Tom, You are right. Almost all our machines were born in 1950 - 1951. They are using the RCA 9030 Soundhead. Very few problems. Only once did we break a fiber gear and that was caused by no oil in the soundhead. And it wasn't the projectionist's fault either. Turns out the tube under the sightglass was clogged giving a false indication that the oil pan was full.

I tried getting all our sound heads changed to reverse readers when the dye track issue came about. But my superiors did some "research" and discovered that dye tracks were never gonna happen and there would be no need to change out. I wish we could. I have even heard that the RCA9030s are tough to retrofit. Anybody know about that?

As for the LEDs. There is not only one by itself, right? Rather something like 36 tiny LED segments that make up the one bright spot. Also heard that over time these individual segments will wink out one at a time having some adverse affect. Though not much. I read somewhere where there is a modification where you can decrease the voltage to make them last longer.

But things keep changing. The longer I have to wait the cheaper and better things will get. But you know what these incandesent lamps are getting hard to find nowdays.

One bright spot is that we have gotten approval to upgrade some of our premier theaters. One of them is at my location. Going all the way up to a Kinoton FP-25E and Dolby Digital. All new equipment, even the screen. EAW speakers. We are looking for something to last the next 50 years.

Bill BuncH
Misawa, Japan

Posted by Mark Gulbrandsen (Member # 72) on 01-13-2002, 12:59 PM:

Ken,
I used to install them left on all the time but that install method was based on the supposed fact that they were going to have a very long life....which they actually do not. Switching the reverse scans and the cat 701's on and off with the automation is a wise idea and can sometimes triple the led life. I've found that they last an average of three years if left on all the time. I have to replace some in Colorado next week that are about that old and the Cat 701's have basically gotten to the point that they only playback some times. I could just crank them up but moving the units to switched AC and replacing them will make more sense especially since its in kind of a remote area. Tripling that almost 3 year figure makes the LED expense miniscule over 9 years, and even less than replacing exciter lamps!
Mark @ GTS

Posted by Ken Lackner (Member # 1002) on 01-13-2002, 01:05 PM:

Mark,

AC?? I thought the LED's had to run on DC. I am surprised that leaving them on all day is so damaging. I would have though that the initial shock every time they are turned on (same for exciters and LED's) would be worse than leaving them on.

Posted by Ray Derrick (Member # 1001) on 01-15-2002, 04:29 AM:

Ken, I think Mark was referring to the type of mains supply, not the voltage on the LED, which is indeed DC.

I know of one technician here who has been installing a relay with a series resistor across the contacts to drop the LED current down to about 10mA when film is not running. He is claiming greatly increased LED life and reduced light level fall-off. The relay is controlled by the projector motor switch so the resistor is shorted out whenever the motor is running. We have not been able to verify if this really makes a difference but it makes some sense given the physical nature of the LED array. This is the essentially same idea as what Mark is doing in relation to running exciters at 10%, which he mentioned earlier in this thread.

------------------
Ray Derrick
President/Chief Engineer
Panalogic Corporation Sydney, Australia
Phone: 61 (0)2 9894 6655 Fax: 61 (0)2 9894 6935

Posted by John Pytlak (Member # 331) on 01-16-2002, 08:11 AM:

William Bunch said: ". But my superiors did some "research" and discovered that dye tracks were never gonna happen and there would be no need to change out."

There was a panel discussion on cyan dye analog soundtracks at last week's ITEA (International Theatre Equipment Association) Seminar in Los Angeles. Representatives of Disney, 20th Century Fox, MGM, Warner Bros., and New Line endorsed the conversion to cyan dye analog tracks, which will require red LED readers. Miramax has successfully tested cyan dye analog soundtracks on two recent features ("Get Over It" and "Jay and Silent Bob Strike Back". According to Ioan Allen of Dolby, cyan dye track prints sent to theatres with red LED readers had no problems on playback.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion