[Boatanchors] Johnson Viking II Fuses

[Rob Atkinson]

I have hams ask me what current capability I use for fuses.  Let's
take a look at what a power supply transformer provides.  It might
have a filament winding for 5 and 6 v., and a high v. winding.
Filament current can be taken from tube data sheets.  A rough idea of
plate current can be seen from the same source looking at typical ICAS
operation.  Just work with the assumption that all the tubes have the
same plate v., even though some stages will have dropping resistors.
That gives a little margin for error for the fuse.  With current and
voltage, calculate power and add it up.  The 117 v. current  demand
can be approximated with the total power sum.  Let's say it's 560 ma.
I'd go with a 1 amp fuse since there's some power lost in the
transformer.  The worst thing that can happen is the fuse blows.  If
that's the case bump it up to 1.5 A.

73

Rob
K5UJ

On Thu, Sep 17, 2020 at 9:43 AM David Stinson <arc5 at ix.netcom.com> wrote:
>
> Johnson Viking II:
> I would like to fuse the primary for the LV transformer.
> Anyone done this?  Recommended fuse value?
> Thanks.
>