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Thanks for all the ideas that came in on this. An objection I had to
installing a HV fuse was that in case a flashover occured right when
that rare DX came in, the down time becomes intolerable. A scheme that
allows fast recovery to get back on the air quickly is the only way to
go. I find it a scary thought to replace a HV fuse in a hurry!
I am making my project enclosure completely air tight, and the only air
inlets are via fine air filters in order to lessen the chances for
external arcs on the tube anodes due to foreign particles passing thru.
Dave Kirby mentioned that a proper HV fuse in the DC output will reduce
the amount of energy dumped by the HV power supply to the flashover.
There is a slow realiziation on my part to recognize this. Yes indeed,
saving on the cost of a HV fuse could be false economy! This fuse
lowers the chances of damaging an expensive PA tube in a flashover. Hey
Dave, that is a serious PA you are building! Please tell us more about
it sometime.
Peter Chadwick's experience with the #40 string of wire for a fuse
sounds interesting, relying on gravity to break up the arc. A similar
idea was suggested by Mark Wilson in the ARRL handbook although I dont
see any evidence that Mark actually tried it.
So I think I will appraise the cost of my PA tubes and then decide which
method of protection to use.
73's
alex samson ke6vkj
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<TITLE>Re High Voltage fuses</TITLE>
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<P><FONT SIZE=3D2 FACE=3D"Arial">Thanks for all the ideas that came in =
on this. An objection I had to installing a HV fuse was that in =
case a flashover occured right when that rare DX came in, the down time =
becomes intolerable. A scheme that allows fast recovery to get back on =
the air quickly is the only way to go. I find it a scary thought to =
replace a HV fuse in a hurry! </FONT></P>
<P><FONT SIZE=3D2 FACE=3D"Arial">I am making my project enclosure =
completely air tight, and the only air inlets are via fine air filters =
in order to lessen the chances for external arcs on the tube anodes due =
to foreign particles passing thru.</FONT></P>
<P><FONT SIZE=3D2 FACE=3D"Arial">Dave Kirby mentioned that a proper HV =
fuse in the DC output will reduce the amount of energy dumped by the HV =
power supply to the flashover. There is a slow realiziation on my =
part to recognize this. Yes indeed, saving on the cost of a HV fuse =
could be false economy! This fuse lowers the chances of damaging =
an expensive PA tube in a flashover. Hey Dave, that is a serious PA you =
are building! Please tell us more about it sometime. </FONT></P>
<P><FONT SIZE=3D2 FACE=3D"Arial">Peter Chadwick's experience with the =
#40 string of wire for a fuse sounds interesting, relying on gravity to =
break up the arc. A similar idea was suggested by Mark Wilson in the =
ARRL handbook although I dont see any evidence that Mark actually tried =
it. </FONT></P>
<P><FONT SIZE=3D2 FACE=3D"Arial">So I think I will appraise the cost of =
my PA tubes and then decide which method of protection to =
use. </FONT>
</P>
<P><FONT SIZE=3D2 FACE=3D"Arial">73's </FONT>
<BR><FONT SIZE=3D2 FACE=3D"Arial">alex samson ke6vkj</FONT>
</P>
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