[Collins] Bucking Voltage

[David Knepper]

I do hope that someone comes forward to tell us if it will work.  I am sure
that what the good Dr. is telling us will work and someone will give us the
steps to accomplish this so our 516F-2's last for ever running on lower
primary voltage.


Dave, W3ST
Secretary to the Collins Radio Association
Publisher of the Collins Journal
www.collinsra.com
----- Original Message -----
From: "Dr. Gerald N. Johnson, electrical engineer" <geraldj@isunet.net>
To: "David Knepper" <cra@floodcity.net>
Cc: <collins@mailman.qth.net>
Sent: Sunday, November 09, 2003 9:10 PM
Subject: Re: [Collins] Bucking Voltage


> There are two 5 volt windings in a 516F-2, isolated from each other and
> from ground. They would have to be unhooked from the tube sockets
> because a solid state rectifier plugged into the tube socket would be
> using a cathode pin for the DC out of the rectifier. The two 5 volt
> windings in series would make a 10 volt buck for the line voltage and
> can carry the current with no problem. They would drop the output
> voltage more than the solid state rectifiers would raise it and would
> lower the heater voltage and the transformer saturation for a cooler
> running transformer core.
>
> There's now way to know a priori which yellow and which slate to wire to
> the other and to the transformer primary. The connections have to be
> developed experimentally. I like to do such connection testing while
> supplying such a circuit with 6 or 12 volts on the primary. Then I don't
> have 1 kilovolt loose to burn my fingers... or worse.
>
> What I'd do, with 6 volts applied would be to try the two possible
> series connections of the 5 volt windings to get maximum voltage. One
> connection will give nothing, the other will give 10 volts with full
> line voltage, a half volt with 6.3 volts applied. Then I'd connect one
> end of the series pair to the transformer primary wire I planned to use
> and see if the voltage from the other transformer primary wire to the
> free end of the filament pair was greater than the primary voltage. I'd
> swap ends of the series pair (until I achieved that condition. Then I'd
> unhook the power feed from that primary wire and make the connection to
> the filament winding permanent (soldered and taped) as well as the
> series connection of the two filament windings, and then apply power to
> the free end of the seriesed filament windings. That's all there is.
> Harder to describe than to draw or do.
>
> 73, Jerry, K0CQ, Technical Advisor to the CRA.
> --
> Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
> Reproduction by permission only.