Over Voltage Protection for Older Equipment

[Ed Richards]

Those of you who have read my posts will recognize me as an advocate of
reducing the power line voltage for older equipment. In my opinion, no
tube-type radio or test equipment should be plugged into the wall outlet.
The voltage at the time of manufacture was 110 to 117 VAC and running it
at today's 122 VAC can overload it causing premature failure of power
transformers, tubes, etc. For instance, a radio designed for 115 VAC
operation and pulling 1.5 amperes consumes a power of 172.5 VA (watts.)
The same radio operating at 122 VAC pulls 194.3 VA (watts.) An overload
of 12.6 percent.  I have been running all my tube-type radios and test
equipment on a voltage reducer for two years and have not had a failure.

In order to extend the life of these fine old radios and make life easier
for their owners, I have put together a cheap, simple but effective
voltage reducer. It is in a 4" X 4" X 3" metal electrical junction box
with two outlets; one for 110 VAC @ 3 amperes (330 VA) and one for 116
VAC @ 3 amperes (348 VA). It operates on the principle of a
series-bucking voltage, using a filament transformer. The voltage to the
radio is reduced by the amount of filament voltage added in series, but
opposing in phase, thereby subtracting from the line voltage rather than
adding to it. This has several advantages over using a resistor to drop
the voltage: (A) It is more efficient. no power is wasted heating up a
resistor...21.8 watts in the example above. (B) Better voltage regulation
as the voltage drop is due to the voltage developed by the transformer,
which is nearly a constant, not the drop across a resistor which varies
with the load. (C) It doesn't get hot like a resistor does. (D) It can be
used for different loads without having to change the value of a
resistor.

Anyone interested can write me for more information, A free schematic,
drawings, a parts list and step-by-step assembly instructions will be
sent by return e-mail.

I am not doing this to make money, but for those who don't want to run
around gathering up the parts and pieces, I offer a kit of all the parts
plus the instructions for $29.95 plus $7.95 S&H.

And for those who are time-challanged, I offer a built and tested unit
for $39.95 plus $7.95 S&H.

Anyone wanting to forward this information to other reflectors has my
permission.

Ed Richards

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