Bell & Howell 708 Headliner Duo Problem

[Westrex]

Hey everyone,

I'm fixing up the family slide projector (could be considered a camera, sort of) which is a Bell & Howell 708 Headliner Duo, and I have a question regarding a part referred to in the manual as the "heat filter".

When it was first powered up last year after sitting for 15 years or so, the fan didn't run and it was shut off, doing so improperly cooled down this piece of glass and it broke so you can't view slides. Now that I got the fan running, would it be safe to remove this piece and turn it off whenever no slides were being viewed or should I buy another 708 and swap the filters?

Note: I'm pretty sure the projector is out of focus, but I'll need to see an image to properly adjust it.

[SUnset2]

That is a combination condenser and heat absorber.  The projector cannot be used without it.  The easiest place to find a replacement is from another similar projector.  I might have some spare slide projector condensers in my junk box, but they may not be close enough.  What I do have is the better model of that B&H slide projector, that I don't need.  It has lenses and carriers for both 35mm and 2 1/4 slides.  PM me, and I will give you a very good deal on it.

[Westrex]

The manual doesn't specify it being a condenser, since it says both condensers are in front of the heat filter (see photo 5, under model 708), therefore it may not be necessary.

I've attached some photos of the manual from an auction website (sorry about the photo angles and blurriness, these aren't my photos).

[TelePlay]

The manual doesn't specify it being a condenser, since it says both condensers are in front of the heat filter

That lens, that cracked, is a condenser that turns the point source light bulb source into a parallel light source evenly illuminating the slide being projected.

"A condenser is an optical lens that renders a divergent light beam from a point light source into a parallel or converging beam to illuminate an object to be imaged. Condensers are an essential part of any imaging device, such as microscopes, enlargers, slide projectors, and telescopes."

The "heat filter" in the 708 is both a condenser that is designed to stop lamp heat from getting to the slide and turns the point source light from the bulb into a parallel light beam evenly projected across the slide.

The front two lenses focus the slide onto the screen.

The reflector behind the lamp just reflects backward light toward the slide.

Poor choice of nomenclature by the manufacturer calling it only a heat filter on the 708.

Thick glass will crack when heated without proper cooling.

[Westrex]

Ah, I see. The fan didn't work when it was first powered up last year, so it must've cracked then. Could I get a generic replacement that's the right size or should I get one from a "beater" projector?

[TelePlay]

You will need a lens that is the same diameter and the same focal length (lens thickness) and capable of some heating.

Buying a non-functional 708 and extracting its lens would probably be much less costly than buying a new lens, if you can find a manufacturer.

It's easier to find 708 projection lenses assembly than the light condenser lens. Doing a bit of searching I found many projection lenses but no condenser lenses.

You can get a complete used 708 for about $68 with free shipping on eBay.

https://www.ebay.com/itm/203734556823

[Westrex]

I found a condenser (not Bell & Howell brand I don't think) that I think is the right size for $8.95, but since I'm not an expert, I'm not sure if this is right. Is this the right part and does it look right?

[TelePlay]

What are its dimensions, diameter and thickness at its center?

Did you measure you cracked condenser, diameter and thickness?

[TelePlay]

You need the exact diameter to fit the mount.

If it is a bit thicker or thinner, it may work but the focal length will be a bit off and that will show up as a slight hot spot in the center of the projected image or a hot ring around the edges of the projected image. By hot I mean slightly brighter than the rest of the projected image.

[Westrex]

What are its dimensions, diameter and thickness at its center?

Did you measure you cracked condenser, diameter and thickness?

Diameter (cracked condenser) is 2 3/8 inches and the thickness (from center) is approx. 5/8 inch, the eBay seller says the diameter is 2 3/8" and the end thickness (I think they meant how thick the edge is, not from the center) is 1/16". It appears to be correct from my measurements, so I guess I'll go ahead and order it to test it out.

Also, I don't need the brightness to be perfect, my family is digitizing the slides, so it would be nice to have a slideshow to see years past.

[TelePlay]

As long as the diameter is the same it will fit.

For the price you quoted, even if it doesn't work, you wouldn't be losing much.

He stated edge thickness so does yours have a lip or edge of the same thickness? That would be the mounting lip.

[Westrex]

As long as the diameter is the same it will fit.

For the price you quoted, even if it doesn't work, you wouldn't be losing much.

He stated edge thickness so does yours have a lip or edge of the same thickness? That would be the mounting lip.

The condenser is also "Best Offer" so I could maybe get it for less  (I hope they package it well). I think he's referring to the mounting lip which appears to be the same dimension.

Thanks for all the help everyone, I'll post an update when I get the new condenser installed.

[SUnset2]

The condenser for sale in the photos doesn't have the blue tint, so it likely is not heat absorbing glass.  This means that the slides will be getting all of the IR, and will be overheated.

My B&H Streamliner 500 Duo has an additional flat heat absorbing glass between that lens and the next condenser element.  The 500 W lamp probably  needs more IR absorbing than the 300W does.

BTW, my offer still stands to sell you my similar projector in good working order for cheap.

[TelePlay]

The condenser for sale in the photos doesn't have the blue tint, so it likely is not heat absorbing glass.  This means that the slides will be getting all of the IR, and will be

Does yours have a separate blue tinted disk like this or is the back of your lens tinted blue?

And, is your lamp blue? Or clear?

[Westrex]

Hey everyone,

The last condenser I bought didn't have the blue tint, so I never installed it (at least I didn't lose much). However, I found a good replacement that is about the same dimensions of the cracked one, and more importantly has the blue tint. The 708 Headliner Duo doesn't have a separate heat filter, the condenser is tinted blue.

here's a link to the one I bought (I'm pretty sure it fits according to my math): http://www.ebay.com/itm/275462065872