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No Holes Added FootKey Mod for 139XLR

Discussion in 'CB Radio Modifications' started by Dmans, May 23, 2018.

  1. Dmans

    Dmans Well-Known Member

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    Because I was recently awarded limited movement of 1 hand, I decided to add a foot key capability to my Cobra139XLR. Being one that generally hates modifications that detract from the stock look of equipment, I spent several weeks planning out this modification- TO BE EASILY DONE AND COMPLETELY REVERSIBLE.

    This 139XLR has been modified for extra channels (for receiving purposes only ;)). Pin 19 of the chip is being switched by the CB/PA switch. EASILY DONE AND COMPLETELY REVERSIBLE. Since I have been in this hobby (1973) and have had many pieces of gear over the years, I have never used a PA function (other than to test a microphone). It doesn't appear I am going to need that function on this radio. (I do have another 3 or 4 radios with intact PA systems if needed)



    As a former guitar player, I have lots of gear laying around. One piece is a dual function pedal switch. It has 2 separate pedals that will switch 2 different guitars into one amplifier or 1 guitar into 2 amplifiers.Both switches can be set to "Latching" or "Momentary". The pedal unit is metal and quite sturdy. I have used 1 pedal of this unit on my Kenwood for quite some time.(Wonder why Kenwood didn't add a PA function?) I decided to make use of that "B" pedal function through the unused PA jack on the back of the Cobra.

    The pic below shows the back of the EXT speaker/PA speaker board. The black arrow pointing to the board is the clipped off wire to the PA speaker jack center pin-the other black arrow. The gray wire runs along the back side of the chassis to the yellow heat shrinked connection to the red wire. The black wire on the rear of the speaker jack circuit board (just below the bypass capacitor) is heat shrinked to the black wire that runs in the tie strapped bundle at the back of the chassis. This is the "ring" connection to the PA speaker jack.

    upload_2018-5-23_16-7-0.png

    The yellow arrow below shows the "ring" connection to the PA speaker board. That wire is clipped off and heat shrinked with the "bundle" at the back of the chassis. The end of that wire is just behind the purple wire in the bundle in the above picture.

    upload_2018-5-23_16-10-17.png

    The picture below is the back side of the mic jack (the yellow box). The red and black wires added to the PA switch(yellow arrows) are connected to a factory 3 terminal strip next to the mic jack.

    upload_2018-5-23_16-20-40.png

    The added wires are tie strapped to the harness that runs from front to back just to the left of the power supply board. The goal was to make it still look factory inside as well. If you look real close you may spot the "receiving" channel mod.

    upload_2018-5-23_16-23-38.png

    Below showing the microphone I put together and use. It did come from R/S (cat. no. 33-1070C) but is lettered "Shure Omnidirectional Dynamic Microphone". I believe I have $10.00 in it from a clearance sale in the middle to late 80's. I use it on the Kenwood 440 with good reports as well.
    The dual cable used was from my 4 track recorder into a PA system and had 2 color coded RCA plugs into 2- 1/4" phone jacks. It now sports 1- 1/8" phone jack, into the Orange 1/4" phone jack(Cobra) and 1 Gray RCA jack into the 1/4" Gray phone plug (Kenwood).

    upload_2018-5-23_16-26-17.png

    Hard for me not to like this project since I am typically on the radio with a cup of coffee in hand.

    73's
    David
     
    Shadetree Mechanic likes this.

  2. Robb

    Robb Yup

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    Nice job!

    But I hate to be the one that tells you this; sorry.
    Most people use the mic plug and wire it externally thru a conversion cable. This way the converter cable can be used for other radios as well. Some companies even make them pre-made; think Heil still does. I made my own, as it was both easy and cheap to do.
     
  3. Dmans

    Dmans Well-Known Member

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    Robb,
    I've seen Heil's version and others. For me less wires out the front is better.
    I guess this is just my version. And cost me zero.
    73's
    David
     
    Robb likes this.

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