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

[Mark C. Stephens]

The elephant in the room thing with me is SAFETY :)
I mean, can this be a fire hazard, what about the insulation breakdown on the secondary winding etc..

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Burt I. Weiner
Sent: Sunday, 7 July 2013 9:28 AM
To: time-nuts at febo.com
Subject: [time-nuts] HP 5370B dropping mains voltage...

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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