                                  EARPHONE


Adding an earphone jack to any radio is quite simple. It requires opening 
the radio's case, drilling a hole in the case or cabinet, and making three 
soldered connections. The necessary tools are a drill (either electric or 
hand-cranked), needle nose pliers, wire clippers, a sharp pen knife, and a 
soldering iron. The 'phone jack itself costs about $1.25 at Radio Shack, or 
about $.35 if purchased from a wholesale parts supplier or at a ham show. A 
small amount of solder and a few inches of hookup wire are also needed. 

It is extremely important to have the power to the radio turned off and the 
power cord removed from the wall outlet if it is an AC radio. Failure to 
observe this elementary precaution can result in injury or even death.

First, open the case of the radio.  It may be necessary to unscrew or pry 
apart the cabinet or case.  Now, locate the speaker and the two wires 
attached to the two speaker terminals.  Choose one of the speaker wires 
(either one is fine) and remove about 1/8" of its insulation without actually 
breaking the wire.  A small pen knife works best for this.  Use wire clippers 
to cut the other speak wire at about its middle.  remove about 1/8" of 
insulation at each of the cut ends of this wire.

Now to connect the speaker wires to the phone jack. Connect and solder about 
6" of hookup wire between the unbroken speaker wire (at the point where the 
insulation has been removed) and the "common" terminal of the phone jack [A 
in the diagram below]. The common terminal is the one directly connected to 
the center hole of the jack. 

Now examine the phone jack.  Its other two terminals form a sort of spring 
clip that makes a closed loop when no speaker plug is inserted. One of these 
terminals connects to the "U-shaped" spring [B]. Connect this terminal to 
the end of the wire coming from the radio circuit board. Connect the other 
terminal, the one with two right-angle bends in it [C], to the segment of 
wire coming from the speaker. Use extra hookup wire if necessary to make 
these two connections in order to be able to emplace the jack at the point 
on the radio's case or chassis desired. 

Now choose where to install the jack on the case of the radio.  At this 
location drill a hole only slightly larger than the diameter of the 
protruding cylindrical part of the jack. Carefully unscrew the round 
retainer nut from the jack, making sure not to lose the thin metal washer in 
back of it. Press protruding part of the jack from the inside of the case 
through the hole just drilled.  Place the thin metal washer on the protruding 
part of the jack sticking through the hole and screw the round nut on tightly 
enough to hold the jack in place securely.

Carefully close the radio case, making certain that the newly installed wires 
stay safely within the radio and do not become clamped between the halves of 
the case.  Power up the radio and tune in a station.  Insert the earphone 
into the jack.  The sound should disappear from the speaker, but play through 
the earphone if the jack was correctly installed.

The idea is that an earphone plug inserted into the jack "breaks" one side of 
the audio signal going toward the speaker and re-routs the signal to the 
phones.



                          REAR VIEW OF EARPHONE JACK
                          

                                      

  ----- "Spring Clip" terminal [B]
                                      .. 
                                    .    . 
"Common" terminal [A]  ------  

 .      . 

  ---- terminal [C]
                                   .      .
                                    .    .
     "U-shaped"  spring clip  ----  ۪
                                       
                                      ---  right-angle clip




                            HOOKUP DIAGRAM TO SPEAKER WIRES
                            

                         to "common" terminal [A] of phone jack
                                            
                                            
                                                   Ŀ /|
         to radio circuit board  Ĵ Spkr./ |
                                 Ŀ-*-Ĵ      \ |
                                                   \|
                                             
                                      to [B] [C] of phone jack

* break in wire


Mendel Cooper
3425 Chestnut Ridge Road
Grantsville, MD 21536-9801
--------------------------
email:  thegrendel@aol.com

Just $1.00 to register the entire SWRADIO package.
