[Hallicrafters] HT-3x transformers

[k6uuz at juno.com]

Another reason I have not seen mentioned is the increase in line voltage
from 115 in the 50"s and 60's to our present standard of 122 Vac. Below
is a short dissertation on the subject.

Over voltage protection for older equipment

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.

Ed Richards <k6uuz at juno.com>

On Tue, 15 Jan 2002 06:16:50 -0800 jim lockwood <jmlckwd at mindspring.com>
writes:
> At 08:56 PM 01/14/2002 -0600, Bob Nickels wrote:
> >I've always heard that HT-32 and HT-37s were prone to power 
> transformer
> failure,
> >but I've been lucky.  Can anyone explain what the failure mode is, 
> and why
> these
> >transmitters seem to fail more often than most?
> >
> 
> 
> Others have provided interesting observations about the psychology 
> and
> probable side effects of accidentally rotating the function switch 
> to the
> "off" position, and then back to "standby".