[Milsurplus] 125 VAC Line? Make Your BA's Happy, Cheap.

[Mike Feher]

Dave -

I am not sure I understand what you mean by the need for a load for setting
up the magnetic field for an auto transformer. Why hook it up bucking? Just
hook it up in series with the input, in an aiding configuration and then put
your AC input across both windings and take your output from the low end to
the junction of the 15 volt winding. 73 - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 

-----Original Message-----
From: Milsurplus [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of
David Stinson
Sent: Thursday, January 14, 2016 12:01 PM
To: milsurplus at mailman.qth.net; boatanchors at mailman.qth.net
Subject: [Milsurplus] 125 VAC Line? Make Your BA's Happy, Cheap.

Got 125 VAC + on you shack's AC power buss?
Ronnie, W5SUM and I worked this problem.

There must be a zillion old, broken Uninterruptable Power Supply (UPS) units
laying around.  These typically have an AC cord going in and AC sockets
going out 
plus circuit breaker, etc.   In 99% of the cases, the
transformers in these units are still good and are perfect for building a
"line bucker."

We found a couple of dead 12 Amp APC units.
The transformers had a 120 V primary,
a lo-current 15 V and a Hi-current 15 V windings.
The lo-current winding is not used, unless you want to light a pilot light
or something.

Pulled the "hot" leads from the dead circuit board and directly powered the
transformer through the circuit breaker.  Wired the Hi-current 15 V winding
in the "bucking" configuration with one side to the junction of the incoming
"hot" and the other side going to the "outgoing Hot" sockets on the back.
Left all neutrals connected together as normal.
If the voltage is boosted instead of bucked, swap the 15V secondary wires.
Mine drops my line voltage from 125 V to 110 V and my boatanchors are happy.
12 A service will run a lot of stuff
and broken UPSs are cheap, so you can add more.

Important Tip:  A transformer "line bucker" acts as an "autotransformer."
To measure the output voltage accurately, you must connect a load- even a
small one.
The load current sets-up the magnetic field the autotransformer needs to
work.

73 Dave AB5S



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