[AMRadio] Swinging chokes

[John Coleman]

I wouldn't think that there would be any design characteristics that would
would specificly have less voltage handling capability for the center tap
than for the ends but I had never thought of it before either.  I have used
many smaller TV style XFMRs in a bridge arrangement with a fifth diode in
series with the centertap for a half-voltage output lifting the negative
lead of the bridge for turn off.  the fifth diode prevents the filter caps
on the half-voltage supply line from being negative charged when the bridge
negative lead is lifted for turn off.  Never had any trouble with secondary
leakage or break down. Also have have nearly aways used the choke of a choke
input in the negative lead and never considered the spikes.  Dumb Luck maybe
or just not something to worry about?  I don't know.

GL, John, WA5BXO

-----Original Message-----
From: amradio-admin at mailman.qth.net
[mailto:amradio-admin at mailman.qth.net]On Behalf Of Jim Candela
Sent: Wednesday, February 20, 2002 8:16 PM
To: amradio at mailman.qth.net
Subject: Re: [AMRadio] Swinging chokes


    I never used negative lead filtering on my AM rigs because I normally
grounded the transformer CT, and use two 3B28's in a FW-CT rectifier
arrangement. I am afraid that a transformer designed to have the CT grounded
might arc out with negative lead filtering. Would a spark gap from the CT to
ground be advisable, or an R-C snubber across the choke to absorb the back
EMF kick when the choke field collapses?

Regards,
Jim candela
WD5JKO

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