[time-nuts] HP 5370B dropping mains voltage...

Burt I. Weiner biwa at att.net
Sat Jul 6 19:27:31 EDT 2013


This is an old trick that I learned many years ago.  By taking a 
transformer, driving its primary from the mains and then feeding that 
transformer's secondary voltage in series (either in phase or out of 
phase) will either add (in phase) voltage to the transformer primary, 
or subtract (out of phase) voltage to the transformer thereby 
reducing the transformer's primary voltage by the amount of the 
buck/boost transformers secondary voltage.  It's important to use a 
transformer for the buck or boost circuit that can handle the amps 
necessary for the particular load.

I often used "Healthy" filament transformers to do the job.For 
example... At one time I had a Kenwood 820S transceiver that I picked 
up in Japan.  Japan's mains voltage was 100 VAC.  When I got back 
home I needed to get the 120 VAC stepped down to 100 VAC to properly 
run this rig.  What I did was to take a Triad multi-voltage 
"Dry-Disk" transformer and connect the primary winding across the 120 
VAC mains.  In this case I used the 18 VAC secondary windings and put 
that in series but out of phase, with the Kenwood Radio's 
primary.  This reduced the 120 VAC going into the Kenwood to about 
102 VAC (120V-18V=102 Volts).  Had I connected the Dry-Disk 
transformer's winding in series and in phase I would've had 138 volts.

I hope this helps.

Burt, K6OQK

>Subject: Re: [time-nuts] HP 5370B dropping mains voltage
>
>
>How Does that Work Robert?
>I mean why out of phase?
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 
>On Behalf Of Robert Atkinson
>
>Subject: Re: [time-nuts] HP 5370B dropping mains voltage
>
>Hi Marki,
>
>Dropping the mains voltage is easy. Get a mains to low voltage 
>transformer. Connect the primary across the mains and the secondary 
>in series opposition (out of phase) with the mains supply. Foar 
>example a 100VA 12V transformer will drop your mains to just under 
>238V with a maximum load of 8A (the current rating of the secondary).
>
>
>HTH,
>Robert G8RPI.

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at att.net
www.biwa.cc
K6OQK 



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