[Hallicrafters] Possible free Source of "Isolation" Transformers

[Phil Atchley]

Hello
Not trying to beat a dead horse but I just "discovered" an isolation
transformer in my junkbox.  This particular item is a Toroidal wound
transformer from a junked out BIG guitar amp head.  It has dual primaries
which for 120VAC are wired in parallel, was fused at 5 Amps in the primary
and should do just fine.

I intend to fuse this unit at 2 Amps Slow Blow which will give me roughly a
120 Watt rating
and put it in a small box with a outlet and a fuse along with a power
switch.

To use this puppy, I separated the two primaries, put an AC power cord on
one primary and a 60 Watt lamp bulb on the other primary (now the
secondary).  The original secondaries are unused.

Testing.  I put 119VAC on the primary and measured the Voltage across the 60
Watt lamp.  It measured 114VAC, a loss of 5 Volts.  I would presume that it
will probably give me about 110VAC with about a 110Watt load (Boatanchor
radio).  This is just about perfect or old radios.  However, I'll be using
it with a Hallicrafters 5R10A AC/DC receiver that takes about 30 Watts, so I
won't get the full benefit of the Voltage drop.

So, you never know, you just might find a "treasure" in that junkbox in the
form of a "lurking" isolation transformer.  (A necessity for old AC/DC radio
work).  Just look for one with dual primaries.  A lot of equipment designed
for worldwide power have these dual primaries.  Look at old stereos,
instrument amps etc.  Considering that the primary fuses in these devices
are for "peak" current, not continious load, take the primary fuse rating,
divide that by two (for a single primary current) then derate somewhat below
that.  Instrument amplifiers are better than stereo home stereo amplifiers
as these are often designed so that musicians can run them with all controls
set on "10" for long periods with no damage.  Of course, high quality
instrument amplifers aren't often junked out for no cause.  This one came to
me sans cabinet (chassis only) and with multiple problems, so was a choice
candidate!

I had need of a isolation transformer but no funds to permit the purchase of
one.  You can also do the same thing with two transformers of the same
Voltage/Current rating by wiring them back to back.  That was my first
intent before I ran across this puppy.

NOTE:  Transformers with "autotransformer (tapped) primaries DO NOT make an
isolation transformer.

73 de Phil  KO6BB
Loving home provided for wayward Boatanchor Receivers
ko6bb at elite.net
Merced, Central California
37.18N 120.29W CM97sh



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