Micdoctor's Step by step instructions for an old
Shure ( 55 / 51 ) style Amphenol MC3M connector cable

Revised December 10, 2015

When you first open the connector package, you will be surprised with the array of parts. In these photos, you become acquainted with the parts. From left to right,

  • Strain Relief Spring

  • Rear Screw Cap

  • Strain relief / ground

  • Mic connector nut

  • Connector Body

  • Tiny Screw

  • Male connector termination


  • Familiarize yourself with the parts, and the order and direction that they go on the end of the cable. Slide the parts on the end of the cable first. Half of the installion errors occur from improper arrangement.


    Next, slide all the parts out of the way down the cable a foot or so to allow working room. Using an x-acto or shop knife, slice the insulation of the cable approximately 2 inches from the end. Split the ground shield in half and twist it as shown. Strip the cable conductors back so about a half inch of insulation is visible. Twist the wire conductors as shown.


    Next comes the "tinning" of the wires. With a heated soldering iron, heat the wires while applying solder. The solder will melt onto the wires and spread. Make sure there is enough solder on the wires to make them "stiff" and easier to insert into the connector end. Choose the thinner of the ground wire twists as the one to go into the connector. The other one will be used to ground the connector shell in another step.


    Arrange the wires, and insert them into the three holes in the connector end. Pull the other ground wire backward and out of the way. In the picture below, Pin 3 is facing outward, Pin 2 is in the rear, and Pin 1 is below. The wiring convention is "Pin 2 is hot, pin 3 is not, pin 1 is ground." Make sure this matches the other end of your cable, whether XLR or 1/4".


    After the wires have been inserted through the connector pins, and are emerging from the other side, pull the wires tight, and then solder the individual pins. Make sure to be thorough, it may take several attempts to get the pins adequately soldered. When satisfied with the connection, use snips to cut off the wires off flush. You may use a soldering iron to round off the solder on the pins.


    Slide the connector body up and over the connector with the ground pigtail pointing out the back. Align the hole in the connector with the one in the body, and screw in the tiny screw. Next, slide the strain relief down to the connector body, and pinch the prongs in until they make contact with the cable. Feed the pigtail ground wire inside the strain relief, and solder the ground wire to the strain relief.


    OK, almost there. Slide the mic connector ring, end ring, and spring up to the body of the connector. Push really hard, and screw the back connector ring at the same time. Depending on how the strain relief was installed, it may either be easy or a real pain to get the connector to fit tight.

    That completes the attachment of the connector. All that remains is testing with a ohmmeter and/or plugging and and seeing if it works. If it doesn't, you are in a world of hurting. Disassembly and reterminating is an exercise in self abuse.




    Connectors and cables (sometimes) available in:

  • The Micdoctor Mart in Signal7Shop

  • These directions are being provided by Micdoctor for those who buy/may buy connectors from Micdoctor. If you receive these instructions from any third party, please send an email to micdoctor@gmail.com











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    Art Graham
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