The plastic ring on Prontor shutters?

[JPD]

Some Prontor shutters have a plastic ring, that I assume is for insulation, next to the flash contact. Inside is just metal with a tiny hole. What is the purpose of this? I have only seen it on Prontor shutters so far.

This is not my camera, but a picture from Pinterest:

 

[Donald Qualls]

I presume you're referring to the part that looks like "natural" urethane just next to the PC sync connector? I think I recall reading this was a secondary connector for a particular kind of flash cable -- used the PC sync plus the terminal inside that ring. Since PC sync stands for "Prontor/Compur" this may actually be an obsolete part of the PC sync standard from the 1940s or 1950s.

 

[AgX]

I think I recall reading this was a secondary connector for a particular kind of flash cable -- used the PC sync plus the terminal inside that ring.

Thus a "bi-pole" solution in contrast to the concentric solution?
However that makes no sense as the inner pole is the life one, the outer the ground. A divided connector for the ground would not need an insulation.
Unless they were switched the other way round, the life pole at the insulated connector.

However, I assume that plastic ring is nothing electrical at all.

 

[Donald Qualls]

Just passing along what I recall.

Entirely possible I remembered wrong. I specifically don't know whether the metal inside the plastic ring is connected to the shutter housing (like the shell of the PC connector) or insulated from it and connected to something else.

 

[AgX]

Here is a photo of a Prontor -S with more detail:
https://www.flickr.com/photos/29504544@N08/5672380312

https://www.flickr.com/photos/29504544@N08/5672694258/in/photostream/



Thus it seems electrical...

The Gauthier service manual calls it "Insulating Bushing". The location over an isolating plate with thereunder an electrical plate that is the live-pole (confirmed by the manual) makes that bushing likely a second live pole. As Donald indicated...

But what for??
Or is there a flash connector that gets its life from inside that enigmatic bushing and the ground from the PC connector?
Wouldn't such connector need its two poles being parallel, and not at an angle (due to being located on a curved surface)? Well, two single-pole connectors (at wires) would work though.


There was a period with flash connectors that existed of 2 male poles at wires, one for the life and one for the ground. You see such at the very first Praktica.
One could think that this Prontor shutter was designed to serve such connectors too. But at the Prontor a male and a female pole are needed.



The best explanation I can offer is that this shutter was meant to serve both a concentric (PC) connector, but also that connector made of two male studs at wires, but added with a hermaphrodite adapter for the ground pole.

 

[shutterfinger]

https://drive.google.com/file/d/0B1sPJkp-MdghVFNtSzhyay1lTkE/view?usp=sharing
There are multiple variations of this shutter. The one in question is a early version. The flash contact strip is connected to the case and insulated by the plastic piece in question. The parts section of the manual shows it as part of the case, not a separate part. The contact strip is connected to the center of the PC socket and is contacted by a spring or part of the delay mechanism depending on the variant of the shutter.

 

[AgX]

Now I am completely confused... to hold any of these plates no seperate bushing is needed. Am I overlooking something?

 

[shutterfinger]

Now I am completely confused.

Excellent!

I did not search the small parts list for the part numbers in the #0 diagram.

 

[JPD]

I'm curious to see what the connectors on the flash cable that uses it look like.

Here is a Prontor II with a different flash connector and it also has this thing. It must be from before the PC standard.

https://i.ebayimg.com/images/g/~pMAAOSwrklVYaCX/s-l1600.jpg