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 Post subject: Gonset Communicator III Drawing Errors
PostPosted: Sep Thu 12, 2019 8:44 am 
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Location: Lincoln City, OR 97367
Greetings to the Forum:

I recently had occasion to dig into my Communicator III documentation in regards to a question on vibrators. While doing so, I discovered that the unit could not possibly work as drawn. After some head scratching and digging into my Communicator III, I discovered the following errors:

1. The interconnect plug that connects the power supply to the transmitter was drawn differently on the power supply schematic and the transmitter schematic. The pin numbering scheme was not the same, even though these are mating connectors.

2. Even if one ignores the different numbering schemes, the unit could not work as drawn and the drawing did not reflect the actual wiring in the Communicator III.

Therefore, I have (from my Olympian heights of power :D ) decided on a third numbering scheme which makes more sense, since it begins from the indexing notch and continues in order around the socket (connector on the end of the power supply cable) clockwise as viewed from the wiring side.

In order to make this work and to clarify the drawings, the following changes are recommended for anyone with a Communicator III:

A. On the power supply schematic, change the pin numbers on the connector as follows:
The first pin immediately clockwise from the notch depicted on the drawing is pin 1.
Number all pins consecutively from pin one, proceeding clockwise around the circle.
Pin 6 should now be the pin on the opposite (counter-clockwise) side of the notch.

B. Print out the following PDF file which contains a drawing segment which can be pasted over the Communicator III 2 meter transmitter schematic, replacing the portion of the drawing containing the plug and the components in the immediate vicinity. Note that the 6 meter transmitter is also different and will require a different overlay which I have yet to construct. (Caveat... since I am not interested in 6 meters, I may not do so, but the 2 meter drawing and the theory explanation to follow should be sufficient to trouble-shoot the 6 meter rig.)
Be sure that you print it actual size. There is a line in blue on the drawing that is 3 inches long. Measure this with a ruler. If it is 3 inches in length, the drawing should fit the 16" X 22" OEM schematic.
Carefully trim the drawing so as to cover the items on the original that need covering, but take care to trim closely so as not to obscure any other part of the schematic.
Affix with tape or glue. Presto... the 2 meter transmitter and power supply schematics will now make sense with regards to the interconnecting plug.

Attachment:
Gonset Com III 2 Meter TX Interconnect Plug.pdf [6.09 KiB]
Downloaded 16 times


NOTE: The drawing on the power supply schematic has the connector pin numbers increasing in a CLOCKWISE direction from the index notch. The transmitter connector has the pin numbers increasing from the notch in a COUNTER-CLOCKWISE direction. Both connectors are labeled as viewed from the wiring side. THIS IS CORRECT!
Remember, the transmitter connector is a SOCKET, and the convention with sockets is to number clockwise from the index on the wiring side. The transmitter connector is a PLUG, and as such, is numbered counter-clockwise from the index notch AS VIEWED FROM THE UNDERSIDE OF THE CHASSIS WHERE THE WIRING IS in order to correctly mate with the socket on the power supply cable.

Understanding the TR system (which is essentially a PTT [push-to-talk] system with a front panel switch duplicating the switch in the microphone and in parallel with it) is important to understanding the changes in the schematics.

Transmit-Receive switching is accomplished by a pair of relays. Their coils are in series and one end of the string connects to ground. The relays are ENERGIZED in receive mode. The PTT switch shorts out the relay power, taking it to ground, which (of course) de-energizes the relays and places the unit in transmit mode. Opening the front panel TR switch or releasing the mic PTT button removes this short and allows power to flow through the relay coils to ground, energizing the relays and placing the unit in receive mode.

The question that caused me concern, especially since it is impossible to make sense of the interconnection scheme as drawn, was "What sort of relay power source doesn't mind being shorted to ground?". After ringing out the actual connections in my communicator III, I had the answer. The negative side of the B+ supply (labeled correctly as B-) does not return to ground anywhere in the power supply chassis. Instead, it is routed to the transmitter chassis, where it returns to ground through the TR relay coils. Under normal receive conditions, there is enough current through the B+ supply to energize the relays and place the unit in receive. Placing the unit in transmit shorts out the relays, bringing B- directly to ground via the PTT or front panel switch. This probably results in a slightly higher transmit B+ and is not detrimental to the power supply, which explains how Gonset can get away with shorting out a relay power supply.

It really is a clever circuit, but it does have an idiosyncrasy of its own. The unusual thing (and the manual points this out), is that the unit wakes up in transmit mode. As the tubes warm up and start to draw current, the relays close and the unit toggles over into receive mode. You are advised to listen for this occurrence to be sure the Communicator III is doing what you expect it to do.

Hopefully, this will be of some help to anyone puzzling over how the Communicator III is put together.

Regards

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Jim T.
KB6GM


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 Post subject: Re: Gonset Communicator III Drawing Errors
PostPosted: Sep Thu 12, 2019 10:46 am 
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Joined: Oct Sun 15, 2006 12:57 pm
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Location: Liberty, Missouri
The Great Zeus, has spoken, on with the games!! :wink:

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 Post subject: Re: Gonset Communicator III Drawing Errors
PostPosted: Sep Fri 13, 2019 12:35 am 
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Joined: Sep Mon 16, 2013 2:42 am
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Location: Tucson, Arizona U.S.A.
My more recent experience with Jones style connectors is that different manufacturers use different pin numbering schemes for otherwise compatible connectors. BEWARE!

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Jim Mueller


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 Post subject: Re: Gonset Communicator III Drawing Errors
PostPosted: Sep Fri 13, 2019 3:08 am 
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Joined: Nov Mon 02, 2009 7:01 am
Posts: 3863
Location: Lincoln City, OR 97367
Greetings to Jim and the Forum:

The connector in question is not a Cinch-Jones connector. It is a round connector with two larger pins like a six-pin tube base, except it is less than 1 inch in diameter. It is on the end of a 4-wire cable that runs from the power supply to the transmitter chassis. There is no numbering visible; only an indexing notch. The pin numbers on the Gonset drawings were different for the same connector and did not match up any way... hence the research effort and the re-drawing.

Regards,

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Jim T.
KB6GM


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