of the pattern. Use medium grade sandpaper to clean up
While holding the coil in a vice, use a hack saw to cut
the seven slits. After each slit is sawed, use medium
sandpaper to clean it out and round the edges of the cut.
This is most easily done by folding the sand paper in half
and passing it back and forth within the slit.
Carefully check that the depth of each slit is the same.
The circular saw will have made a hole in the center of the
coil. Install a 1/4” x 2” long screw in the hole with the
head against the smooth side. Secure it with a nut. You
will wrap the coil leads around the extended threads of
the screw to keep them out of the way while winding the
To make winding L2, wind 5” of #28 enameled wire
around the screw, then pass the remaining length through
a slit. This will be lead 1. Pull it tight on the other side and
pass it down through the next slit. Repeat this until you
have made about 65 complete turns. Note that counting
the wire turns on either side represents roughly half the
total number of turns.
End winding with the wire passing back through the
slit where you started. Fold the next 10” of wire in half,
wrap it around the screw with lead 1, and pass the
remaining wire through the same slit. The folded wire will
be the coil tap lead 2. Continue winding in the same
direction for about 13 turns, finishing at the same slit as
before. Cut the wire to 5” and wrap this lead around the
screw. This will be lead 3. Winding L2 is complete.
Leaving 5” leads, follow the same procedure for L1,
starting and ending where you finished the L2 winding.
Wind about five turns in the same direction. The starting
lead is number 4 and the ending lead is number 5. When
all windings are complete, dab a little quick set epoxy at
the outer edge of the slit to keep lead 5 from unraveling.
Unwind the leads from the screw and gently pull them
aside. Drill out the center hole to 3/8”. Cut a 3-1/2”
length of 3/8” round dowel. Insert one end in an electric
drill and sand the rotating dowel evenly until the nylon
collars fit snugly over it. Cut 2-1/2” of the sanded portion
and set it aside; refer to Figure 8.
Glue a collar to the underside of the chassis base
to hold the dowel firmly in place. Use Wiring Diagram
5 to connect the coil leads to terminal strip TS-1 and
binding post J4. Solder all connections. Insert the
dowel through the chassis base into the glued collar.
Slip one collar on the dowel, then the coil (lead side
down), and a second collar to hold the coil in place as
shown in Figure 8.
Use spray-on glue to attach the tuning scale and
labels of Figure 9 to the front assembly. Lastly, install
the knobs to the front of the radio. This completes
Before applying power the first time, it is a good
idea to check for a major short circuit. Before inserting
32 May 2015
■ FIGURE 8.
Side view of
■ FIGURE 9. Tuning and
other front panel labels.