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#81
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.
#82
What are its dimensions, diameter and thickness at its center?

Did you measure you cracked condenser, diameter and thickness?
#83
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?
#84
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

#85
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?




#86
Quote from: G-Man on March 21, 2024, 02:36:46 PMThe wiring diagram that I downloaded from the TCI Library did not contain the NYTel warning about this scheme. https://www.telephonecollectors.info/index.php/browse/wiring-diagrams/western-electric/desk-stands/2125-desk-stands-51mod-tl/file

That diagram, although contributed by "anonymous", appears to be from the NYT addendum.

Quote from: G-Man on March 21, 2024, 02:36:46 PMEven so, most of us already knew of this circuit's limitations but if the user intends to only use one instrument at a time, then there should not be any appreciable transmission losses when only one instrument is in use at a time.

Even with 2 500s off-hook on the same line, there is an impedance mismatch.

Quote from: G-Man on March 21, 2024, 02:36:46 PMNote that the NYTel admonition also states that two additional high-impedance ringing bridges on the same line were still acceptable.

It says "two high-impedance bridges" -- I.e. 2 ringers total, not 2 additional ringers,

Quote from: G-Man on March 21, 2024, 02:36:46 PMAlso, NYTel used this scheme only to save money by not having to invest in replacing obsolete equipment in order to maximize its financial return.

The NYT addendum is dated 1946. They were trying to keep up with post-war demand.

Quote from: G-Man on March 21, 2024, 02:36:46 PMTo reiterate, in general, I still think it is a terrible idea to mix and match these subsets and instruments.

Ditto goes for "cheater subsets" and "mini-networks"  but it's definitely their choice to do as they please.

I agree.
#87
General Discussion / Re: 12-button Princess® with ...
Last post by TelePlay - March 21, 2024, 08:05:25 PM
Your photos of the phone failed to upload.
#88
Quote from: Westrex on March 21, 2024, 07:20:19 PMThe 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.
#89
General Discussion / 12-button Princess® with hard...
Last post by Robert Gift - March 21, 2024, 07:25:18 PM
$3.99 at ARC Thrift Store
Yellow
Thoughthat a 12-button telephone would have plug-in coiled cord and RJ11 jack in the base.

On Touchtone pad edge:
35E4A
 5-72
On the base appears
2792B 
R57O

Bottom appears old brown rubber pad.

30?-foot gray cord with spade lugs.
Light bulb insert is missing.   Light bulb resistor looks good.

Can I find the light bulb insert?
Thank you.
#90
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).