[AMRadio] Millen High Voltage Connectors


Ed Swynar gswynar at durham.net
Mon Jan 9 16:00:35 EST 2006


Hi Dave,

I solved the problem of HV B+ arc-overs here by exclusively using NOTHING
but good-quality SO-239 coax receptacles, & RG-8 coax lines for the B+
leads, terminated in good-quality PL-259's...

Works like the proverbial charm --- have yet to encounter ANY arc-over
failures since adopting this approach universally at my station in the late
70's...

~73~ Eddy VE3CUI - VE3XZ

PS: Emphasis on the words "...good-quality" --- NONE OF THAT CHINESE JUNK
here!!!






----- Original Message -----
From: "david knepper" <collinsradio at adelphia.net>
To: <amradio at mailman.qth.net>; <boatanchors at mailman.qth.net>
Sent: Monday, January 09, 2006 3:50 PM
Subject: [AMRadio] Millen High Voltage Connectors


> My homebrew transmitter,  designed by Stan, W3TGR now a silent key,  is
> going through exhaustive and often frustrating testing.  Stan used lots of
> shielded wire - you know the Belden stuff that is deteriorating over time
> with brittle insulation on the wire. I had to replace several leads
because
> the center conductor was shorting to ground when the insulation became
> brittle.  So it goes ...
>
> Today, I thought that I had finally debugged the unit - pair of 813's
> modulated by 805's - but I heard the troubling sound of high voltage to
> ground.  Measuring the Millen connectors to ground revealed a short.  Here
> the Millen connectors on the modulator were arcing to ground on the
> secondary side of the modulation transformer running from the high voltage
> through the secondary winding to the PA amplifier.   I am using those
light
> tan units that are supposed to be better than the red connectors.  Stan
used
> these connectors on the PA amplifier, the modulator deck, and the high
> voltage power supply.
>
> I suppose that under modulation that the peaks exceeded the voltage rating
> of the Millen connectors.  Once before many years ago, I had the same
> problem.  However, these connectors are often used in homebrew
construction
> projects as described in the ARRL handbook.
>
> Any ideas out there other than to go with ceramic feedthrough insulators.
>
> Perhaps, it is because of their age and the insulation is breaking down.
> Who knows!
>
> Thanks
>
> Dave, W3ST
> Publisher of the Collins Journal
> Secretary to the Collins Radio Association
> www.collinsra.com - the CRA Website
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>
>
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