[Hallicrafters] Power transformer temperatures

[rbethman]

My turn on the soap box.

I have some number of Heathkit TXs, RXs, Hallicrafters TXs, and RXs. 
 The SX-101 MK III for example says "115V to 125V".  I will grant 
that "SOME" show ratings less, BUT many of the older rigs had the 
range to handle these voltages simply because the power companies 
were much smaller than today's.  They weren't as fastidious 
maintaining voltage and frequency as the larger companies do now.

My SX-101 Mk III does indeed read a little higher than the voltage 
charts printed.  But since it was designed with a "range", it would 
make sense to have only a single voltage printed on the charts.  How 
else would you expect to have a readable chart?  Since components, 
i.e., resistors, have tolerances of up to 20%, these reading can ONLY 
be an approximation anyway.

Bob - N0DGN

-----Original Message-----
From:	k6uuz at juno.com

Let me get on my soap box. I feel that high voltage leads to 
excessive
temperatures and subsequent failures. Most of the tube-type equipment 
was
manufactured when the line voltage was 110 to 117 VAC. Running it on
today's 122 VAC can lead to failures. Some people think that because 
your
equipment may be rated for something like 105 to 125 VAC you are 
within
limits and safe. When a range is listed it usually is the design 
voltage
+/- some amount. In this case the design voltage would be 115 VAC. If 
you
have any doubts, measure the filament and B+ voltages and compare to 
the
service manual. A quick and easy way is to pull a tube and measure 
the
voltage on the socket filament pin. If it is more than 6.3 or 12.6 
volts
you are running over rating. You can get info on building or buying a
simple but efficient voltage reducer from the BAMA site, about 1/2 
way
down the page. Thanks for the bandwidth.

 Ed Richards

On Thu, 3 Apr 2003 18:46:02 -0800 Waldo Magnuson <magnuson at mac.com>
writes:
> Does anyone know what the normal range of temperatures is for power 

> transformers?  I've been monitoring the temperature on an audio
> amplifier (a Craftsmen RC-2 which drives a pair of 6V6s).  I 
measure
>
> the temp at the mid-point on top of the power transformer with my
> wife's digital food probe and it has been reading up to 120.0 deg. 
F
>
> after a couple of hours.  Is this normal, or hot, or cool, or ?  Is 

> there any guess on how much the cover on my SX-42 power transformer 

> increases its temperature.  I've heard that over time the
> temperature
> tends to weaken the insulation amoung the transformer windings much 

> in
> the same way as it dries out capacitors.  Any thoughts?  Thanks.
> Skip Magnuson
>
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