[Boatanchors] HV fusing in amplifiers

[Sheldon Daitch]

Another option is to use overload relays in the cathode circuit.

Most, if not all, high power transmitters, use overload relays
in the cathode cirucuit, adjusted to pull in at some current level
over the maximum that should ever been seen by the circuit, to
kill the power supply.  Gates used them even at the one KW
level, the BC-1T, for sure, in both the RF and modulator stages.
And we have them in our TX units up to the 500KW level.

They are a little more complicated than a fuse, but are self resetting.

73
Sheldon
WA4MZZ

GEORGE MORTON wrote:

> Gents - Fusing HV line is quite simple!  5 ohm 5 watt
> resistor (flameproof variety) in series with HV line right off top of the
> choke will blow under excess current load before costly tubes will expire.
> Brgds to all, Geo
>
>     From: "Rbethman" <rbethman at comcast.net>
> To: <Boatanchors at mailman.qth.net>
> Sent: Wednesday, May 04, 2005 4:58 PM
> Subject: [Boatanchors] HV fusing in amplifiers
>
> > Group,
> >
> > Has anyone thought about high voltage fusing in an amplifier or "old" BA?
> >
> > Usually there is a choke in the RF output leg to ground, in the event that
> the plate blocking cap fails.
> >
> > Yes, we usually have power supply fuses or circuit breakers.  BUT - what
> will get fried?  How do you protect all that?
> >
> > I've got ONE HV fuse by GE.  Its design voltage is 2400V.  It is rated at
> 7A, which is obviously a ridiculous value.  HOWEVER, even IF it was a
> reasonable current rating, it is HUGE!  It is 11" long and 2" in dia.
> >
> > Where in the world would you even mount it?
> > --
> > Bob - NØDGN
> >                        Bob Bethman - NØDGN
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