--------------------------------------------------
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
> Shorting the B+ to ground is exactly what a crowbar protector does!!!!!
> You discharge the supply allowing something else like a fuse that may
> explode if need be
> to protect the tube.
## Ok, what his circuit described below is... is a cro-bar... and not a fuse
!
All as this is going to do is remove B+ from the tube [same as a HV fuse],
then
create a new problem... a solid B+ to chassis dead short. Now something
else has to handle the dead short... like breaker in the 240 line, etc.
Unless
a 2nd hv fuse is inserted between sec of xfmr.. and diode bridge, you will
stress
the FWB.
## IMO, a HV fuse would be simpler, and much faster. Glitch R limits the
fault current,
hv fuse then interrupts the fault current.. and all in < 2 msecs.
## BTW.. sson now has 5 kv hv fuse [ same 13/16" ends, that fit a 3/4"
clip],
in both 1.5A and also 3 A.
http://www.surplussales.com/Electrical/Fuses/ElecFuses-4.html
## mating 3/4" fuse holders, with end retainers, [ so fuse can not migrate
out] are here
http://www.surplussales.com/Electrical/Holders/ElecHold-1.html
## The 5" long 5 kv [that's 5 kv AC / 7kv dc] rated fuses, fit the
above clips very tight,which
is what u want. With the end stop retainer's, the fuse can be mounted
Horz or Vert.
## silver plated clips mounted to glazed ceramic stand offs. In the
interest of safety, I use
TWO B+ meters. One in RF deck, [ effectively on output side of HV
fuse].. and 2nd one
inside the HV supply itself, wired between INPUT of hv fuse.. and B-
## when HV fuse blows open... B+ meter in RF deck reads ZERO V. B+ meter
in HV
supply STILL reads full B+ voltage. RF deck + HV supply are two separate
box's,
and may or may not be in the same rack.
later.......... Jim VE7RF
>
> Bill
>
> I have thought a #30 wire or somewhat smaller wire was stretched inside
> a grounded piece of copper
> pipe such that there would be no discharge when HV was applied would be a
> great fuse. This is because if
> an arc in the tube would vaporize the wire and producing a plasma that
> would short the B+ to
> ground via the surrounding copper tube or pipe. Also, it would be easy to
> replace.
>
> 73
> Bill wa4lav
>
>
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