Artifact Evaluation - microphone connector

[Ric Gillespie]

During the 2017 Betchart expedition to Nikumaroro led by former TIGHAR archaeologist Tom King, a TIGHAR member collected an artifact that Joe Cerniglia has independently identified as an Amphenol microphone connector.  The artifact was collected under the provisions of TIGHAR's Antiquities Management Agreement with the Republic of Kiribati but it was not sent to TIGHAR HQ and we have not been involved in, or even aware of, its identification.  Joe has promised to send the artifact to TIGHAR not later than mid-November along with a number of others collected during the 2017 trip. 

Without notifying TIGHAR, Joe has now posted a lengthy report on the artifact on Tom King's "Amelia Earhart Archaeology" blog.  Tom King is no longer associated with TIGHAR. He was removed from the TIGHAR board of directors on August 31, 2018 and cancelled his membership in TIGHAR the next day.

Please review Joe's report.  Is this artifact of any significance?  Thanks.

[Martin X. Moleski, SJ]

Without notifying TIGHAR, Joe has now posted a lengthy report on the artifact on Tom King's "Amelia Earhart Archaeology" blog.

Here is a permalink to "Connections of a Wayward Microphone Connector."

[Bill Mangus]

Found these pictures of a Western Electric Model 13-C transmitter.

http://www.kn4r.com/kn4r/Western_Electric_13-C.html

The very last picture is interesting.

[Ric Gillespie]

Once we have our hands on the artifact we should be able to answer some of these questions.

[James Champion]

To label it a microphone connector is to imply that it was used on a radio. But a radio microphone connector needs three pins minimum - Mic, return(gnd), and PPT(push-to-talk). Most radio microphone use four connections so there is no electrical 'pop' when the microphone is keyed. From what I can tell of the pictures it may well be only a two-pin version of the Amphenol connector. That would make it more like a microphone as found on a sound-system. I've also seen the two pin version used for speaker connections. That would mean it could have been used on a public address system or film projector.

And yes - it's in too good of shape for being in the open on an island. Plating on these is bright nickle, and not chrome (chromium).

[Ric Gillespie]

Thanks Jim.  I think we're making progress. The Coast Guard LORAN station had a 16mm movie projector and regularly showed Hollywood movies flown in by the re-supply PBYs.  They would often invite the locals to come watch the movies.

[Ric Gillespie]

Jim, could you provide links to some sources for this information?  If we can eliminate this artifact as being from an aircraft we need to have documentation.

[Jerry Germann]

James,

       I believe Joe mentions in his report that the found connector is of the one prong version. (as below) minus external threads.

https://www.surplussales.com/Images/Connectors/Microphone/cna-80-M1_1_lg.jpg

[Ric Gillespie]

James,

       I believe Joe mentions in his report that the found connector is of the one prong version. (as below) minus external threads.

https://www.surplussales.com/Images/Connectors/Microphone/cna-80-M1_1_lg.jpg

In his report, Joes says:
"The 80-Series connector was listed in Amphenol catalogs, parts distributor catalogs, and advertisements as a microphone connector."  but the documentation he provides shows otherwise.

He says:
"The 91-Series was a deluxe model. It came with 3-or 4-prongs. The 80-Series was an intermediate model, with 1- or 2-prongs. The artifact is an example of the 1-prong variant of the 80-Series. The 75-Series was the entry level model, with 1-prong only."

Joe does not provide a photo of the prong end of the artifact but his Photo #15 appears to confirm that the artifact has a single prong. Jim Champion's statement that "a radio microphone connector needs three pins minimum - Mic, return(gnd), and PPT(push-to-talk)" is actually supported by the images in Joe's report.

Joe's Photo#5 is an image from a 1936 catalog advertising a three-prong connector as a "microphone connector."  No series number is mentioned.
iIn Joe's Photo #19, the one and two-prong Series 80 connectors are labeled "contact connectors."  The three and four-prong Series 91 versions are shown separately as "microphone connectors."

Unless Joe can produce documentation showing a single-prong Amphenol connector marketed as "microphone connector" it is safe to conclude that he has misidentified the artifact. It is a "contact connector" and not associated with a radio, aircraft or otherwise.

[Friend Weller]

Found these pictures of a Western Electric Model 13-C transmitter.

http://www.kn4r.com/kn4r/Western_Electric_13-C.html

The very last picture is interesting.

Noting the Cinch-Jones style connector as seen in the photos of the WE13-C that Bill linked, do we have information on how the cockpit control head was connected to the cabling that ran to and from the transmitter in the aft section of the aircraft?  I have looked at the WE13-C transmitter schematics (with and without modifications) comparing them to the photos and at the faceplate drawings of the control head but (forgive me if I've missed something) I have not seen a drawing, schematic, or photograph that shows how the control head interfaced with the wiring loom running between the two units.  If the connector is not disqualified by a physical characteristic (incorrect plating for the time period, etc.), perhaps it was part of the control head/interconnecting cable loom assembly.  I do note that the remnants of the shielding braid in Joe's report appear to be of the heavier, stiffer variety used in fixed radio applications (such as a wiring loom) rather than the more flexible shielding used in disconnectable items such as speakers, microphones, headsets, etc., often with a woven fabric jacket.

[Ric Gillespie]

If the connector is not disqualified by a physical characteristic (incorrect plating for the time period, etc.), perhaps it was part of the control head/interconnecting cable loom assembly.

Would a single-prong contact connector work in that context?

[Friend Weller]

Would a single-prong contact connector work in that context?

The large Cinch-Jones connector as seen in the photo of the transmitter (and referencing back to the schematic pinouts) has not only the +12 filament, +/- Dynamotor supply (forgive me, I don't recall the B+ and C- voltages), and chassis ground connections but appears to also be the connection point for the Morse key, mic audio and PTT function.  The control head if I recall correctly (on the transmit side of things), has the PTT function, Morse key, and the mic jacks.  None of these functions including the transmit frequency selector, or any of the receive-side items require huge amounts of current to be switched through compared to the supply voltages of the transmitter or receiver.  If that is the case, smaller connectors can be and are often utilized, especially in the tight confines of the cockpit (yeah, I've got a little design experience there, too).  Depending on the design of the control head, single-contact connectors such as the artifact in question could be used as the need for the larger connectors is neither needed electrically, desired spatially, or simply due to weight concerns.  There could have been one for the mic, one for the PTT and/or one for the Morse Key or some combination such as a 2-pin for the mic/PTT and a 1-pin for the key, all on the back panel of the control head as connection to the wiring loom.  The schematic tells us how it is wired, but a photo or other diagram would tell us how it was connected physically.  As in so many cases with the disappearance, a single photograph would be the answer to many questions!   

I hope this all made sense.....rushing between meetings....and wishing I had all the documents open in front of me!

[Ric Gillespie]

The radio control head in the cockpit appears to have been a custom mash-up for NR16020 and no schematic seems to have survived.
If we accept the hypothesis that the single-prong contact connector found in the new village came from the back of this unit we have to explain how it could have gotten there. Did the early settlers have sufficient access to the wreck and sufficient interest to dismantle the instrument panel?  If so, why haven't other cockpit-related artifacts turned up? 

[Bill Mangus]

This is the forum site where I found the pictures of the transmitter.  The second entry has some schematics (which I have long-since forgot how to read) that may be useful.  The pictures are in the last entry.

http://antiqueradios.com/forums/viewtopic.php?t=178640

Perhaps contact with the individual doing the restoration might be in order.

[Ric Gillespie]

If I understand the problem correctly, the potential use of a single-prong contact connector is in the control head in the cockpit, not in the transmitter.