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An uninformed person might have attached
an a.c. plug to the power cord of a radio that is
clearly equipped with a vibrator power supply.
Or the set, for reasons to be discussed, may legitimately
be equipped with an a.c.-compatible
plug that was not intended to be plugged into
an a.c. outlet. Let’s take a look at some of these
d.c. sets so we can understand and appreciate
the purpose for which they were designd.
❖ 110-Volt D.C. Radios
This is a very rare class of antique radio,
with few examples surviving today. Probably the
best example is the Philco Model 46, which is in
the same style cabinet as the very well known
Philcos 70 and 90. The 110-volt d.c. radio is a
legacy of Thomas Edison’s early electrification
of our major Eastern Seaboard cities in the late
19 th century. 110 volts d.c. is what his dynamos
supplied, and so 110 volts d.c. is what all lighting,
appliances and motors used in the system
had to be designed to operate on.
Even though the much more efficient a.c.
distribution system invented by Nikola Tesla
had become dominant by the early 20th century,
the large installed base of d.c. appliances kept
d.c. power in the mains in some areas of certain
cities for decades. A New York Times article of
November 14, 2007, titled “Off Goes the Power
Current Started by Thomas Edison,” describes
the cutoff of the last d.c. power being distributed
in New York City.
The extreme longevity of these pockets of
d.c. service explains why radios like the Philco
46 were still being made in the early 1930s. The
46 had no rectifier circuit – only a hash filter at
the power input – and so plugging it into a.c.
would result, at the least, in non-operation.
However, inexpensive a.c.-d.c. radios began
to appear on the market just a little later in the
decade. These little sets would operate happily
on either type of current, requiring only reversal
of the plug to correct failure to operate on d.c.
❖ Six-Volt Farm Radios
Before the era of rural electrification began
in the mid 1930s, life on most of America’s
farms was, in many ways, still very similar to
what it had been for the prior 200 years. Though
the actual work of farming had become easier
for those who could afford tractors and other
machinery, the lack of electric power meant
lantern or lamp light after dark and backbreaking
work for the housewife with no labor saving
appliances.
But during the earliest days of radio
broadcasting, the farmer was at no particular
disadvantage compared to his city cousins. The
city listener might be connected to a power line,
but it did him no good when it came to radio
listening. He still needed to rely on an array of
bulky and expensive batteries to operate his set.
By the late 1920s, the latest radios could be
plugged into the wall – IF you happened to be a
city dweller. Farm folks still needed their A, B
and C batteries and the rat’s nest of connecting
cables. Rural electrification was still over five
years away.
But some relief was at hand with the appearance
on the market of radios which, like
A Wincharger could be had at a deep discount
if a radio were purchased at the same time.
auto sets, operated from a 6-volt car battery that
provided all necessary voltages. Borrowing from
auto radio technology, these sets incorporated a
vibrator power supply. Their advertising made
the important point “Only two wires to connect!”
But the mere acquisition of a six-volt radio
and an extra car battery did not, of itself, make for
convenient radio listening. The battery was going
to need regular recharging, and transporting that
heavy messy thing to a service station in town
was not the most attractive of options. Enter the
Wincharger, a wind-driven generator which, as
its ads proclaimed, supplied “firepower” from
the air. [For a full account of these radios see
“Old School Wind-Powered Farm Radios”
pages 16-19 MT April, 2011 -- Editor]
The Wincharger sold for about $20.00,
complete with its own steel tower. And this price
was often deeply discounted for customers who
purchased a radio at the same time. The little
wind generator did a creditable job of keeping the
one battery charged but, for those who wanted
a charging system with a little more reliability,
another ten or twelve dollars would buy a gaspowered
generator.
❖ The 32-Volt System
A single car battery might supply enough
power for a radio and perhaps one or two lights,
but the family that required power to operate
several household appliances and tools and
wished to wire their entire home, and perhaps an
outbuilding or two, would probably choose a 32-
volt system. Power for the system was stored in
a group of heavy glass-cased batteries arranged
on a rack in the basement.
Not only did such a system have the ability
to supply much more power, but the power could
be distributed over smaller wires, and for greater
distances, without appreciable losses. The batteries
usually were kept charged by a gasolinedriven
generator that would automatically start
up and top off the batteries every time a light or
appliance was turned on. However, some systems
used large wind driven generators instead.
Now, here’s how many rare 32-volt radios
and other appliances were accidentally
destroyed. When wiring up a house for a 32-volt
system, the usual practice was to use the plugs,
sockets, and other wiring devices suitable for a
110-volt installation. This was done in anticipation
of the rural electrification that had begun
transforming farm life by the mid 1930s. When
the power line came to the neighborhood, all
the installer had to do was disconnect the feed
from the 32-volt system and connect the 110-volt
cable in its place.
Of course, all 32-volt lamps, appliances and
tools had to be trashed or put in the attic – to be
replaced by their 110-volt counterparts. Much
later a collector might come across a long-agodiscarded
32-volt radio with its 110-volt plug
still in place and...well you can imagine the rest.
D.C. Farm radios looked much like 110-volt
a.c. plug-in types – sometimes leading to accidental
destruction!
Some 32-volt radios had vibrator power
supplies to provide the necessary high voltage
and these are easy to spot. More subtle are
those that use 32-volts throughout and have
no special power supply. If you suspect you
are dealing with a 32-volt set, one sign to look
for is the absence of a rectifier tube and power
transformer. Another is the presence of multiple
audio output tubes. Sometimes as many as four
were used to provide adequate volume at the low
plate voltage.
See you next time when we will try to
shoehorn some replacement electrolytics into
the tiny Arvin chassis.
August 2012 MONITORING TIMES 63