I am in the process of finishing an 8877 amp that was started by a friend of
mine about ten years ago and given to me when he moved away. It was based
on the QST article in Sept. 1986 by K8RA. I may have additional questions
as I get around to testing but for now I have a question about the surge
protection in the power supply where MOVs are installed per the QSTarticle.
If I understood W8JI recently, Tom said MOVs should not be installed in a
piece of equipment, forcing the surge to green wire ground, but rather
should only be at the service entrance (or single point ground?). The power
supply is fed from a dedicated 220 volt circuit, which passes through my
Polyphaser single point ground panel located directly under the shack. The
panel is grounded 5 feet away to a ground rod, which is bonded to the
service panel via a ring that goes partially around the house. On the
single point ground panel I have a Polyphaser 220 volt lightning suppressor
box,as well as a 110 volt one, and all my shack power comes from them. So I
believe I am properly protected from lightning as well as transients on the
220 volt line. So my question is, should I remove the MOVs from the 220
volt input in the power supply (where they clamp from line to chassis
ground)? In case it matters, I feed the power supply from a 220 volt line
with ground, no neutral.
In case you decide to look up the original article, please note that the
author improperly used the chassis as the neutral to get 110 from. i.e.
where he needed 110 he used one side of the 220 line and chassis. I note
that in the 2006 ARRL handbook, the same author has corrected that practice
and now utilizes a 220 line with neutral.
Rick K2XT
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