- a set of heavy duty (solid bus wire is hard to bend!) wire bending
pliers with smooth, round jaws. The jaws should be tapered (have a
variable diameter along their length), with a range of diameters to
suit screw sizes from about #4 - #10.
- accurate, flexible steel, narrow, measuring ruler. A miniature steel
tape measure with a width of 114" or so is excellent for this
- a small steel square, with a blade length of 4' or so. An accurately
cut piece of rigid metal about 3" x 4" will also work for
- a small V-shape file
- a single-edged razor blade (best) or small pair of sharp scissors
(OK) for cuffing the insulated tubing.
- a set of bending jigs. These will be made up as required from the
- a good soldering iron of about 50 watts. The Weller constant temperature
TCP series is excellent
- bus wire and insulated tubing. To wire or rewire a radio, you will
use a lot of material, so be sure to estimate lengths conservatively.
- two soft wood blocks (preferably pine)
- rosin core solder some small tywraps
Figure 1. Cutting Wire and Forming Eyelets
Word About Accuracy and Neatness
In this work, ACCURACY and NEATNESS are all-important. These concepts
ACCURACY: When using 12 or 14 ga solid wire, the is very little room
for error, as there is virtually no "give" in the wire to
compensate for even small mistakes. Even if one could "force"
the wire to compensate for inaccuracy, neatness would almost certainly
suffer. Further, the wire is stiff enough to damage components if attempts
are made to force it where it doesn't want to go.
NEATNESS: The human eye is relatively tolerant of some anomalies, such
as absolute sizes or distances. It is, however, excruciatingly sensitive
to others, such as parallelism and end-on alignments.
It is precisely the latter which can make or break the final appearance
a bus wiring job. If two adjacent wires are not parallel, or a right
angle bend is a bit out, the human eye will register it instantly. This
work takes time and cannot be rushed. Like any other learned skill you
do get better as you go along. It is quite rewarding and can be done
a few wire runs per evening over a period of time.
One interesting side effect of doing your own bus wiring is that you
develop a very critical eye for the workmanship on other sets. In general,
the work done by home-builders, and even some manufacturers, in the
1920's was not of a very high standard!
There are three basic bends in bus wiring: the angle, eyelet and crimp.
The angle (usually 90) is used to change direction, the eyelet is used
under screw heads and for tee wire joins. For both of these bends, jigs
are required to ensure the right angle or eyelet is accurately located.
The crimp connection comes in many forms and will be mentioned later
An eyelet takes two bends, the first as in Fig. 1C and the second as
in lD. For the first bend, the wire should be gripped so that it is
flush with the edges of the plier jaws, as in Fig lE, then make the
bend as in 1C. The direction of the bend is important - it should be
clockwise so that tightening the screw head does not tend to open up
the eyelet when the screw is tightened. To make the second bend, rotate
the pliers 180 degrees inside the eyelet. regrip the wire and bend slightly
in the counterclockwise direction to form a symmetrical eyelet. Make
sure that the joint is tightly closed after each bend.
It is difficult to give any general description as to how to do crimped
connections (as to component tugs, etc.), but be careful to ensure that
they are neat, mechanically strong and have a good appearance. For appearances
sake, the wire should approach the lug on its centre line. A typical
crimp connection is shown in Fig 2.
2. A Typical Crimp Connection.
Before doing any wiring, there are a few things to get out of the way
of the Bending Pliers
The jaws of the wire bending pliers must be permanently marked so that
bends will be accurate and consistent. The object here is to locate
the positions on the tapered plier jaws where the wire must be held
to obtain consistent "inside" bend radii suitable for common
machine screws. Some antique wire bending pliers were actually manufactured
with "stepped" jaws, but I have never seen one of these except
in a 1922 magazine ad. You will need a sample machine screw in each
of the sizes you intend to use, usually #4, #6, and #8. For each screw
size and wire size for which you wish to bend eyelets:
- estimate where on the plier jaw that the wire should be placed to
give a circle which will just slip over the machine screw, and make
a mark with a fine pencil.
- bend an eyelet as above and check the fit with the machine screw.
This should be an easy slip fit, but not too loose, as the appearance
- If the eyelet is the wrong size, cut it off, make a new pencil mark
on the plier jaws and bend another.
- repeat this process until accurate eyelets are obtained consistently.
Once this is accomplished, using the file to make a fine, permanent
reference mark on the plier jaw. This mark should be filed deep enough
so that you can just feel it as you slide the wire over the plier
- To make the mark more visible, fill it with white lacquer stick.
The final result is illustrated in Fig 3.
3. Plier Jaw Marking.
Up Eyelet Bending Jigs
The amount of added wire required to form an eyelet depends on the radius
of the hole and the wire gauge. If an eyelet is to be formed at the
end of a wire run (ie one end is already fixed), the wire must first
be sheared to the correct length and then the eyelet formed. The purpose
of an eyelet jig is to permit accurate determination of where to cut
the wire so that the formed eyelet will end up in the right position
at the end of the wire. If the location is not accurate, the wire run
will have to be redone. To make an eyelet jig (one required for each
eyelet and screw size):
(1) Cut (shear off square) both ends of a piece of wire about 3"
(2) File a fine reference mark on the piece of wire exactly 1.00"
from the end on which the eyelet is to be formed.
(3) Bend the eyelet for the screw size using the correct position
on the jaws of the "calibrated" pliers.
(4) Measure the distance between the centre of the eyelet hole and
the reference mark from step (2). Subtract this measurement from 1.00"
- this is the amount of extra material required to form the eyelet
on the end of the wire.
(5) File a file reference mark on the wire, exactly the distance determined
in step (4) from the wire end opposite the eyelet, and fill with white
lacquer stick. The eyelet thus formed is handy to identify the jig
and to hang it up on a small board. One eyelet jig will be require
for each wire size and machine screw size. Test the jig by bending
a few eyelets as below.
Up Right Angle Bend Jigs
The thickness of 12 and 14 ga wire is such that it must be taken into
account when making 90 degree bends. In bending angles, select one bend
radius that you like from those marked on the jaw of the bending pliers
and use it consistently. A right angle bending jig can be used to accurately
indicate where the wire should be gripped so that an accurate right
angle results. The jig is used to indicate the distance before the bend
that the wire should be gripped.
To make an angle jig (one required for each wire size):
(1) Bend an eyelet into one end of a 3" piece of wire (to hang
(2) Make a reference mark in pencil about 1/8" from the end opposite
the eyelet Bend a right angle as described below. If the centre line
of the wire does not fall on the intended path, adjust the mark and
(3) Once the reference mark is correct, mark the jig with the file.
This completes the tool kit. Next, we will look at how to use the jigs
we have made up.
Eyelets and Angles
Bending an eyelet at the end of a wire run:
(1) Accurately mark on the wire (with pencil) the location of the
centre of the screw head which is to receive the eyelet. See Fig.
(2) Align the reference mark on the jig with the pencil mark from
(1), and make a second pencil mark flush with the end of the jig on
the wire to he cut. Cut the wire and bend the eyelet as already described.
Making a right angled bend along a wire:
- Accurately mark the wire at the centre line of the new path. See
- Align the end of the jig with the mark from (1), and make a second
mark on the wire to be bent at the jig reference mark. Grip the wire
at this second point and make the bend.
- Check the accuracy of the bend angle with the small square and adjust
The above will work equally well with square bus wire if you are fortunate
enough to find any!
4. Using Wiring Jigs.
Down to Work
After the above preparations, it is time do some actual wiring! Before
starting a wiring job, a little planning will be helpful. This will
require research to determine the correct appearance of the original
set (many sets have suffered the indignity of several amateurish rewiring
jobs), or at least to find out what was usual for the vintage of the
radio. If this is a repair (only a few wires are to be replaced) try
to match the existing as closely as possible. When you remove old wiring,
save any insulated tubing.
- Determine the wire size from existing wiring, publications, etc.
For example, the early Leutz superhets (1922 - 24) used 12 GA wire.
If you are building a 'new" set, 12 GA wire looks nicer but costs
a bit more and requires more work. Estimate the amount of wire required,
if you are not sure, start with a 100' roll of 12 Ga.
- If the set used the snazzy black insulated tubing, estimate the
amount required. If you are not sure, use the tubing. Start with about
50' of insulated tubing to suit the wire used.
- If the set used solder lugs. you should use them too, If you are
not sure, leave them out.
If this is a repair job, remove the offending wiring, saving any insulated
tubing. Make a note of each wire run as you remove it
If this is a complete rewiring job or a new" set:
- make up a wiring diagram (a drawing showing the routing of the wire
runs) from the existing wiring, blueprints or from other documentation
of the set
- if you do not have a schematic of the set, make one up wire-by-wire
as you disassemble it
- remove all components from the baseboard and front panel. Clean
and/or restore the baseboard and panels as required (now is an ideal
time to do this, as they are easy to work on). Do the same for the
components. (Re)assemble the baseboard, front panel and components.
All components must be mechanically secure. If this is a 'new"
set, decide on the component layout.
Wire the set in a logical sequence:
- busses: ground, filaments, B+, screen voltages
- other long or complicated runs
- the remainder
When 12 and 14 GA bus wire comes from the manufacturer, it is inevitably
wound on a small spool. After being unwound, it must be straightened
before use. To accomplish this, secure one end of the wire to a fence
post, unroll the entire length of the spool (or as much as you can),
and repeatedly draw the wire between two soft wood blocks (pine is good)
over its full length until it is smooth and free from ripples and small
kinks. Do not use too much pressure on the blocks and wear gloves to
protect your hands. Once the wire has been straightened, recoil it using
a diameter of 2 or 3' and secure with a tywrap. Once recoiled, handle
(1) Use right angled bends if at all possible. Point-to-point wiring
is obviously better from an RF point of view, but this isn't the way
it was done. Even a 1/2' jog should be done with two right angled bends.
(2) If you are using insulated tubing, it must be cut to size and slipped
on the wire before the next bend, eyelet or crimp. Allow about 1/8'
of clearance from the crimp, eyelet or right angled bend. Cut the tubing
cleanly and squarely, using the single edged razor blade and a wood
(3) When making solder joints, appearance is very important as they
are there for all to see. Joints should be bright with a good solder
fillet. Clean the flux from each solder connection using alcohol and
0-tips. Work in a well ventilated area.
(4) When making a tee connection to another wire, bend as small an eyelet
as you can (you can make a jig for this if you wish), open it up enough
to slip over the wire being connected to, and then crimp it tight and
solder. This gives a nice symmetrical appearance to the joint
(5) When starting a wire run, estimate the length of wire required and
cut an adequate length from the coil of straightened wire. Do not attempt
to work directly from the coil itself!
(6) For each eyelet, bend etc. as you progress along the wire run, reinstall
the wire each time you do something, then remove it completely and perform
the action. Attempting to work on the wire while it is in place is not
really an option.
(7) Do not solder anything until the wire run is completely installed
for the last time
Figure 5 A Typical Wiring Run
The wiring method described above may seem overly complex on first reading,
but don't let this discourage you from trying it out. As you gain more
experience and practice, you will find that things go quite quickly,
and that you will develop a very good eye" for gauging wire lengths,
Eventually, you may be able to dispense with some of the jigs entirely,
and do most things from experience. I am sure that in the old days,
the people who wired these sets for a living could probably do the work
in their sleep!
I can personally assure you that, if you take the time to do an A-1
job rewiring a battery set in the manner described, it will become one
of the most appreciated radios in your collection. In a way, it was
kind of sad in the mid to late '20s when bus wiring gave way to stranded
hookup wire, wire harnesses and finally printed circuits.
A sample of the finished product which you can expect using the techniques
described above is show in Fig 6.
6: A Receiver Wired Using the Techniques Described
Wiring Materials and Sources
$7 (Electro Sonic)
Bus Wire, 14 ga.
$80/m (US direct)
$34/c, $275m (Electro Sonic)
Bus Wire, 12 ga
115/m (US direct)
$50/c (Electro Sonic)
Tubing, 14 ga
$15/c (US direct)
Tubing, 12 ga
$20/c (US direct)
Bimbach 81 Schmitt Boulevard Farmingdale, NY 11735 (516)420-0400
Minimum direct order $100
Electro Sonic 1100 Gordon Baker Road Willowdale, Ontario M211
3B3 (800) 567-6647