Johnson Navigator Questions

Freeberg, Scott (STP) scott.freeberg at GUIDANT.COM
Mon Nov 23 11:46:52 EST 1998

Hi Steve,

Thanks for replying to my questions post.  Ok, let me see if I have it
straight.  With the meter switch in the grid position, start tuning the
exciter for a small increase, then switch the meter to plate and make sure
the dipped plate is staying below 150 ma or less.  Switch back the meter to
grid and continue increasing exciter, again switching back to the plate
position and making sure the dipped plate is 150 ma or less.

When I tune for max grid current with the meter in the grid position,  the
meter slams again the right side of the meter, so your procedure makes
sense.    Its a little different from the Valiant where I peak the exciter
in the grid position and then switch to plate and dip the plate BUT, do not
go back and detune the exciter to reduce off plate current, rather reduce
plate current by adjusting the loading controls.

Yes, your advice about slow tuning makes good sense.  Replacement
transformers are hard to find!  Thanks for your advice.


Scott WA9WFA in Saint Paul Minn

> -----Original Message-----
> From: Steve Harrison [SMTP:ko0u at]
> Sent: Friday, November 20, 1998 7:53 PM
> To:   Freeberg, Scott (STP)
> Subject:      Re: Johnson Navigator Questions
> It means to peak the grid current but not so far as to exceed about 150 mA
> of plate current. This helps to limit the plate dissipation while you are
> reading the next instruction in the manual and finding the knobs to
> twist/turn :o)
> Actually, tubes and parts being as expensive and hard to find these days
> as
> they are, I'd reduce that "150 mA" to something more like 100 mA or even
> less. That is, start tuning the machine up real gradually, trying to never
> stress anything; it'll probably last longer than otherwise.
> Remember, too, that if tubes like 6146s or sweep tubes arc over internally
> while tuning the machine, the plate current drawn for a moment can blow
> other parts such as HV rectifiers and/of plate trahsformers. It always
> pays, these days, to take it easy and slowly with these old veterans.
> 73, Steve Ko0U/1

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