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June 1936 Radio-Craft
 [Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
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It is hard to believe in 1936, a
time when cars were huge and dashboards had almost nothing behind them except some
heater ducts, that access to something as simple as a radio speaker would be difficult.
Evidently it could be, according to the first-place winner of "Short-Cut" in
Radio-Craft magazine. There was not then the rat's nest of wires, air bags,
and control cables found in modern autos. Voluminous trunks back in the day, and
engine compartments that you could almost stand in while changing spark plugs (I
once had a 6-cylinder, 1970 Chevy truck that I could do that with) were typical. Compare
that to modern weenie trunks barely large enough to hold groceries and engine compartments
accommodating front-wheel-drive transmissions and dozens of emission-reduction add-ons.
The "Calibrated Audio-Frequency Alternator" is a particularly hard method
for generating AC at adjustable frequencies.
Looking through these old articles really makes you appreciate modern conveniences.
Of course that doesn't explain why some of us like to work with vintage equipment
and have to do things that hard way. These dated 'hints and kinks' subjects can
come in handy since as back in the day, a lot of times when you need to fix or replace
something on, say, a
restored vacuum tube radio, there is no off-the-shelf component
readily available.
See also "Short-Cuts in Radio" from the December 1936 issue of Radio-Craft.
Short-Cuts in Radio
First Prize .................·$10.00
Second Prize ............... $5.00
Third Prize ................... $5.00
Honorable Mention
Experimenters: Three cash prizes will be awarded for time- and money-saving ideas.
Honorable mention will be given for all other published items. Send in your best
"kinks"!
Fig. 1 - Handy service speaker.
First Prize. - $10.00
External, "Servicing" Car-Radio Speaker. The 1936 Philco radio sets
for Ford cars are used with a speaker which is installed under the header plate.
If the set has to be removed for service, it is a long job to take out the speaker.
In such cases the speaker shown in Fig. 1 will be found very handy, and may
be made up in a short time. Any small speaker with a 6 V. field may be used, with
a cable and special plug. The plug is made from a discarded tube base, with the
prongs sawed off, and a molded-type 6-prong socket. The latter is cut down as shown,
and bolted to the tube base, after connections have been made to the cable.
For auto sets that have other plug or socket arrangements adapters may be made.
A. E. Pasbrig
Second Prize. - $5.00
Fig. 2 - Tuned input circuit.
Fig. 4 - Increasing charging rate.
Fig. 5 - Vernier screwdriver
Fig. 7 - Emergency soldering.
Fig. 8 - Detachable radio set.
Fig. 9 - Removable clip.
Fig. 10 - Stand-off insulator.
Fig. 11 - Wide-range trimmer.
Fig. 12 - Socket prong cleaner.
Fig. 13 - Cheap shielding.
Increasing Car-Radio Sensitivity. Some makes of car receivers have a
small primary on the antenna coil. This primary is usually designed for average
performance with all kinds of antennas, and it was thought that improved performance
could be obtained by some sort of tuning arrangement. That shown at Fig. 2A
was tried and worked to perfection. The 100 mmf. condenser, small dial and knob
were mounted on the front of the receiver case as shown in Fig. 2B. Some sets
may not have room on the front for the condenser, but since it does not have to
be changed often it can just as well be mounted in any other location.
This arrangement greatly increases the response at the high-frequency end of
the band, but the increase may be noted over the whole range. It will probably be
found that the setting is not quite the same for opposite ends of the band, but
a good average may easily be worked out.
E. G. McCollum
Third Prize. - $5.00
Calibrated Audio-Frequency Alternator. Having need for a source of A.C.
of known frequency, I made a simple machine from a portable phonograph, the general
layout being shown in Fig. 3. A 9-in. gear wheel is mounted on the turntable,
and a (Brandes) headphone unit is used as a pickup. The phone is used without the
cap and diaphragm, and is mounted on a heavy lead block so that it may be moved
for best position. The pole pieces are set so that they are parallel-to, and just
clear, the gear teeth, and they must be even with any 2 of the teeth.
The speed of the turntable is 80 r.p.m., so 12,000 teeth pass the pole pieces
per minute, or 200 per second, giving a 200-cycle note. The output may be amplified
to any level.
Cal Brainard
Fig. 3 - Tone source.
Honorable Mention
Car-Radio "A" Drain Compensator. When the car is in motion, this device
increases the charging rate of the generator 5 A. when the car radio is turned on.
A second cutout is used, and, when connected as shown in Fig. 4, operates when
the car radio switch is turned on. This shorts out the 2-ohm resistor in series
with the field coil. With most generators this will raise the charging rate the
required amount. The armature is adjusted to spring back when the, load of the receiver
is removed.
Harold G. Russell
Honorable Mention
Vernier Screwdriver. Some adjustments which have to be made with an
insulated screwdriver are very critical. The device in Fig. 5 enables one to
make these with the greatest ease and accuracy. The dial is a "K-K" unit and a 4-in.
piece of rod, either metal or insulation, is fastened in the large rotating member
of the dial. The end of the rod is filed flat to fit into the screw slot. This tool
cannot be used on very tight screws unless the dial friction is exceptionally great.
(No Name)
Honorable Mention
Fusing the Power Line. This attachment will save the Service Man much
embarrassment by preventing an accidental blowing of fuses in the customer's home.
As seen in Fig. 6, it is simply a box with 2 sockets for fuses and 2 toggle
switches to short, the fuses if they blow. (Use the self-restoring fuses mentioned
in past issue of Radio-Craft, and you will not need these switches - which should
be used with great circumspection. - Editor) An ordinary outlet is also included.
Should any shorts occur in the trouble lamp, tube tester, or the receiver under
test, the fuse in the box will blow instead of the one in the customer's fuse panel
(perhaps in an inaccessible spot!). The fuses should not he higher than 5 A. rating.
Eugene Kingrey
Fig. 6 - "Safety" fuse box.
Honorable Mention
Emergency Soldering.
When working on an auto receiver, it is sometimes very unhandy to use an electric
soldering iron. In such cases I use a piece of lead from a pencil, and a pair of
test leads, with clips on each end. A clip of one lead is fastened to the chassis
of car or radio, and the other clip to the work to be soldered, as shown in Fig. 7.
The second connection is fastened respectively to the ammeter and (the opposite
end) to the pencil lead, which may be about an inch long. Simply bring the pencil
lead in contact with the work and apply solder.
George J. Coppock
Honorable Mention
Making the Car-Radio Set Quickly Detachable. Car receivers of the type
which bolt to the dash may be made quickly removable. This is done by means of keyhole-shaped
openings cut in the dash. The head of the mounting bolts should pass through the
large part of the hole, while only the shank passes through the small part. To remove
the receiver it is only necessary to loosen the bolts and lift the case slightly
when the bolt heads, or nuts, will pass through. This system may he used on either
single- or multiple-bolt mountings. See Fig. 8.
E. T. Gunderson, Jr.
Honorable Mention
Handy Clip. This device, which is fully explained in Fig. 9, is
very handy and saves a lot of time. The new clip unit slips onto the end of the
test-lead point, but may be removed at will.
Neil Hollinger
Honorable Mention
Inexpensive Stand-Off Insulator. A post from a discarded Ford Model
T magneto, mounted as shown in Fig. 10. serves as an excellent stand-off insulator.
The post must be cleaned thoroughly; the spring is then removed, and the bottom
sawed off.
Barton Wood
Honorable Mention
An Adjustable-Capacity Trimmer. Most experimenters find that the usual
type of trimmer is not efficient over the whole shortwave band. A trimmer used for
bandspread which is satisfactory on the high-frequency band, will have too low a
capacity to be of any use on the lowest band, and vice versa. An improved trimmer
is shown in Fig. 11, which can he used efficiently over the whole range of
the receiver. The shaft pulls in and out for wide variations of capacity, such as
are needed when changing from one band to another, while the usual rotary motion
is used for actual bandspread action. Spring A keeps the shaft from sliding too
easily.
Wm. G. Wheat
Honorable Mention
Prong Cleaner. I have serviced sets with the fault of "cutting out"
when playing, then suddenly coming on again. The trouble has often been found to
be caused by dirty socket prongs. A good cleaner may be made, as seen in Fig. 12,
by dipping a 1/8-in. dia. wooden dowel several inches into a glue pot, then rolling
the dowel in fine sand (emory dust is conductive and should not be used). Allow
this to dry overnight, and you have a fine socket prong cleaner.
O. L. Halstead
Honorable Mention
Wire Shielding. Old (or new) auto copper oil line, when well cleaned
inside and out makes fine shielding, if used with well-insulated wire. It can be
obtained in many sizes and is easy to solder. See Fig. 13.
Alfred J. Murphy
Posted July 17, 2024
(updated from original post
on 3/1/2017)
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