[AMPS] Re High Voltage fuses

[Kenneth D. Grimm]

> Alexander Samson wrote:
<snipped stuff>
> 
> 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.

I've done this for years.  I just used a couple of big ceramic standoffs
and mounted them a couple of inches apart down in the power supply area
of the relay rack..  With very fine wire (#40 is very fine) it works
like a charm.  Choose the wire size according to the fusing current that
will provide reliable operation of the amp, but melt when the current
limit is exceeded.  I believe there is a wire table in the ARRL
Handbook.

 
> So I think I will appraise the cost of my PA tubes and then decide
> which method of protection to use.

Now I can't find any fault with this approach.  However, I've been
partial to big, ugly, and relatively cheap tubes such as 4-1000, 3-1000,
813, etc. and the #40 wire fuse gave me the protection I needed.  Unlike
Peter, who undoubtedly knows what he is doing, my projects tended to arc
and bang with considerable regularity until I get them "tamed."  So I
have seen the #40 wire fuse work many times.  By the way, I'm not sure
gravity has a chance to do anything.  Best I can tell we are talking
about virtually instantaneous vaporization of #40 wire!

73,

-- 
Ken K4XL
grimm@lynchburg.net
Boatanchor Manual Archive - ftp://bama.sbc.edu or
ftp://198.28.36.115/pub

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