1970s Kodak Carousel Slide Projector Operation Question

Going back to my days in elementary school and seeing various types of projector used...

My habit has always been to shut the lamp off and leave the fan running for a couple of minutes. Generally, I will feel the temperature of air coming out the vent with my hand and let it run until the exhaust air cools off. This is usually 1-2 minutes.

As I said, I've always done it with slide projectors, movie projectors, and overheads. I still do it with overheads at work, which are the only type of non-digital projector we still have.

There must be something to it, too, as all the digital projectors I've worked with run the fan for a short time after you shut the lamp off also.

Thanks. That is what I used to do, too. I have not used the projector in many years. I checked Kodak's manual on-line, and was surprised to read:

To shut down, • remove and store the tray • slide the power switch to off Your projector will remain warm for several minutes

The manual listed the "fan" switch setting, but made no mention of when to use it.

http://resources.kodak.com/support/pdf/en/manuals/slideProj/carousel_user_manual.pdf

For a very long time, it was said to turn off the bulb and let the fan cool the projector down.

Then, a few years before slides became a nearly lost art form, the "best practice" was said to be to turn everything off and let the projector cool naturally WITHOUT MOVING OR JIGGLING THE PROJECTOR BEFORE IT DOES COOL OFF.

The reasoning was that the vibration from the fan or moving it might cause the hot bulb to fail.

Frankly, I rarely had a bulb fail when not in use either way...

Brief case projector from TMC (link)

For a very long time, it was said to turn off the bulb and let the fan cool the projector down.

 

Then, a few years before slides became a nearly lost art form, the "best practice" was said to be to turn everything off and let the projector cool naturally WITHOUT MOVING OR JIGGLING THE PROJECTOR BEFORE IT DOES COOL OFF.

 

The reasoning was that the vibration from the fan or moving it might cause the hot bulb to fail.

 

That "best practice" does not make sense.

When the projector is in use, the fan is running, and vibrating.

And it would seem to me that you want to cool down the bulb faster, so that you can move the projector (and put it away) without breaking the filament.

How LONG will it take to cool down sufficiently, when the fan is not running? 5, 10, 20 minutes?

For a fixed position projector, you could let it cool down without forced air.

But I can't see doing that with a projector that you had to pack away after the projection session.

So I always did as Ben did. I turned the switch to fan, and let the fan run until the air coming out was close to room temp or at least mildly warm, and not HOT.

This seems to be one of those things where the "best practices" theory guys clash with the reality guys who have to deal with the equipment in the field.

Asked a friend who knows more about indandescent bulb design and construction than I could ever hope to know.

His take is that, first of all, the fan is essential operation with size vs. wattage and "confined" construction of a projector to keep the lamp from dimpling. I can vouch for this, as I've had a lamp dimple(on an Argus projector, not Kodak) when I didn't think it would matter that the one I installed was a bit longer than the specified size.

He also said that shutting off without running the fan would be fine, but that running the fan wouldn't hurt anything either. When I mentioned that I sometimes want to case the projector within a couple of minutes of shutting it off(something that someone else here mentioned) he agreed that this WOULD be a good reason to use the fan to cool it off. Otherwise, if the projector is going to stay put, fan or no fan after shutting off the lamp doesn't make a difference.

BTW, as a subjective observation, after going through several Carousels/Ektagraphics, I'm now running I think an Ektagraphic III that I got as a freebie. It's the first halogen slide projector I've owned, and I can pretty safely give halogens a ringing endorsement. Given that projectors these days are cheap to free, I think it's worth hunting out one of the late model Carousels or Ektagraphics. Aside from the better illumination, it feeds MUCH better than any Carousel I've used(especially with my stack loader, which I use fairly often). I also put a Buhl lens on mine, which cost me a whopping $10 at the local camera store.

The fan (while the projector is running) also prevents the film from melting.

Without question, and if you have ever had a fan fail while the projector is running, you'll never forget it. Very fast slide meltdown. The "fan on only" setting supports the cool down after use process.

For a very long time, it was said to turn off the bulb and let the fan cool the projector down.

 

Then, a few years before slides became a nearly lost art form, the "best practice" was said to be to turn everything off and let the projector cool naturally WITHOUT MOVING OR JIGGLING THE PROJECTOR BEFORE IT DOES COOL OFF.

 

(snip)

As well as I know, both are right.

Best is to turn it off and leave it without moving it until it cools.

That might take a while, as there is no fan to speed the cooling,

maybe 15 minutes or so.

Second best is to let the fan run, cool off the bulb faster, so you can move

(put away) the projector sooner. As well as I know, this isn't much worse,

but much easier for most people. Maybe two or three minutes.

Banging the projector around with bulb hot or cold is probably not

so good for it.

I have a few lenses for mine, that I bought over the years on eBay, when I probably didn't need them.

I have 3 inch and 2.5 inch lenses, good in small rooms when the screen is close.

I think I also have a mirror lens for rear projection.

I have a few lenses for mine, that I bought over the years on eBay, when I probably didn't need them.

 

I have 3 inch and 2.5 inch lenses, good in small rooms when the screen is close.

 

I think I also have a mirror lens for rear projection.

Yeah, I think that for the average home, at least one short focal length lens is a good idea. The Buhl I mentioned above I think is 10.5", and in the living room at home with the screen against one wall, I end up with the projector in the next room to get things to a decent size. It's great larger lecture halls and conference rooms, though. I keep meaning to look for a short high quality lens, but it hasn't been a high priority for me. I'll projecting from the next room over the awful Kodak zoom lenses that shipped on a lot of these projectors(even the high end Ektagraphics) any day.

I also think it's interesting-I projected for a long time with whatever lens was on the projector when I got it. After getting my first "good" lens, I was amazed at how much more "alive" a good, sharp transparency looks keeping all else the same. That's also not to mention the fact that the ones I've used generally project a noticeably brighter image at the same size.

I have a Buhl mirror lens also, which I've used exactly once. You don't NEED one to properly do rear projection(you can just flip the slides) but it's handy if rear projection is only an occasional thing so that you can still load slides normally.

Yeah, I think that for the average home, at least one short focal length lens is a good idea. The Buhl I mentioned above I think is 10.5", and in the living room at home with the screen against one wall, I end up with the projector in the next room to get things to a decent size. It's great larger lecture halls and conference rooms, though. I keep meaning to look for a short high quality lens, but it hasn't been a high priority for me. I'll projecting from the next room over the awful Kodak zoom lenses that shipped on a lot of these projectors(even the high end Ektagraphics) any day.

 

I also think it's interesting-I projected for a long time with whatever lens was on the projector when I got it. After getting my first "good" lens, I was amazed at how much more "alive" a good, sharp transparency looks keeping all else the same. That's also not to mention the fact that the ones I've used generally project a noticeably brighter image at the same size.

 

I have a Buhl mirror lens also, which I've used exactly once. You don't NEED one to properly do rear projection(you can just flip the slides) but it's handy if rear projection is only an occasional thing so that you can still load slides normally.

The standard Kodak lenses that shipped with Carousel and Ektagraphic projectors were the "kit lenses" of their day--adequate for many users and cheap. Buhl and Schneider, among others, made much better lenses to fit these otherwise excellent projectors at higher price points.

Yeah, I think that for the average home, at least one short focal length lens is a good idea. The Buhl I mentioned above I think is 10.5", and in the living room at home with the screen against one wall, I end up with the projector in the next room to get things to a decent size. It's great larger lecture halls and conference rooms, though. I keep meaning to look for a short high quality lens, but it hasn't been a high priority for me. I'll projecting from the next room over the awful Kodak zoom lenses that shipped on a lot of these projectors(even the high end Ektagraphics) any day.

 

I also think it's interesting-I projected for a long time with whatever lens was on the projector when I got it. After getting my first "good" lens, I was amazed at how much more "alive" a good, sharp transparency looks keeping all else the same. That's also not to mention the fact that the ones I've used generally project a noticeably brighter image at the same size.

 

I have a Buhl mirror lens also, which I've used exactly once. You don't NEED one to properly do rear projection(you can just flip the slides) but it's handy if rear projection is only an occasional thing so that you can still load slides normally.

If I remember from some conferences, there are modified projectors, maybe not by Kodak, with xenon arc lamps instead of the usual lamp. Otherwise you don't get enough light for a big screen in a conference room.

Some Kodak lenses are designed for the curved field of a slide without glass. Reversing the slides will curve the wrong way. Besides that it takes a long time if you have a whole tray, or many trays, full. The one time you used your mirror lens is one more than I have used mine. I did use the 2.5in and 3in at least once, though.

When did Kodak switch to halogen lamps for Carousel projectors?

I was not so long ago looking at service manual for them, found that it might

be later than I thought. Or maybe it is just that the ones with built-in reflector

are later than I thought.

In any case, I believe that the "let the fan run" method dates back to before

halogen lamps, when it might have been more important.

The "cool down without fan and without moving" might be best for

halogen lamps, though often one is in a rush to put things away.

The bulb is not the only thing at risk. Without the fan, the bulb stays hot enough to melt film and plastic parts of the projector unless the fan is running. Turn the bulb off and leave the fan running until cool.

That might be true for older lamps, but I suspect not for halogen lamps.

Non-halogen bulbs are larger, and so closer to projector parts, and might stay warm long enough.

Even the lamp glass can overheat pretty fast.

For halogen lamps, the bulb is designed to be hot, as it is necessary for the process to work.

(The halogen, usually iodine, reacts with tungsten deposited inside the bulb, into

tungsten iodide vapor. That only happens at high temperature. Parts nearby have

to be designed for that temperature.

The popular ELH bulb, and others used with Kodak projectors, have a dichroic reflector

that reflects visible light and transmits IR. Good for film (less IR), but the inside of the projector

gets the IR and has to survive it.

Otherwise, from the Stefan-Boltzmann law, radiant heat is the fourth power of absolute

temperature, so falls of pretty fast as things cool, especially the lamp filament.

Note that many halogen lamps don't have a fan at all. (That is, ones used for general

lighting and track lights.)

It is not uncommon for halogen replacement bulbs, even LED replacements, to destroy automobile parking and tail light fixtures when used inappropriately. Some LED headlights have finned heat exchangers and built-in fans.

So in a few words, high intensity lamps of any sort get very hot, and stay hot just as long as their incandescent counterparts. It is prudent to allow cooling time with the fan running. While desk lamps don't (typically) have cooling fans, their power is typically under 20 watts. Projection bulbs are 80 watts and up, as high as 600 or so.

Regarding the Stefan-Boltzman law, room temperature is still 298 K. Horses dry out eventually, but we don't put them away wet.

Desk lamps might be 20W, but floor lamps are commonly 300W, and work lamps 500W.

Globe Electric 500W Portable Halogen Yellow Work Light-6050401 - The Home Depot

and all without fans. The wire shield on the front, and commonly over the bulb on floor lamps,

is to keep flammable materials from getting too close.

The fixtures are designed to keep the bulb at the appropriate temperature, not too hot,

not too cool, with normal convection cooling on the outside of the fixture.

From: Halogen lamp - Wikipedia

they commonly run with the inside of the fused quartz tube at 540C.

(Though not being a black body, Stefan-Boltzmann doesn't apply.)

The filament is probably close enough to a black body, though.