Over Voltage Protection for Older Equipment

[Charles W. Morehouse]

Hi ED,
Please send the schematic. Restoring an SX-28A and want to protect it. The line voltage
here was up to 130 volts. Complained and they reset the voltage regulators back to 125 v.
But still I agree that the old ladies can't stand that much voltage. Many TX and 73.
Wayne;
W4GBW

Ed Richards wrote:

> 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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