[AMRadio] Viking Desk Modulation


Todd, KA1KAQ ka1kaq at gmail.com
Tue Jan 15 10:56:30 EST 2008


On Jan 15, 2008 1:02 AM, Jay Bromley <jayw5jay at gmail.com> wrote:
> Tom,
> It has been a long time since I owned one, but be sure to look for the
> obvious things like wrong regulator tube in wrong socket.  Check bias and
> screen voltages, but use great care!  My mod iron had two taps, one would
> make slightly more than 100%, but required more audio drive.

Hey Jay, good to see you on here. I use many of your 'improvements'
for the KW-1 on my transmitter with great success, passed along to me
by Uncle Ed WA3PUN in the days well before the internet. Many thanks!

The mod iron in early Viking KWs was the same identical iron used in
the KW-1, and has the 12,000 P-to-P winding and....18,000? The lower
number being the less efficient but 'more audio/more drive' winding.
This is what I use on mine. Later models Vikings used what appears to
be the same iron, but with much larger insulators in place of the
original small ones. Maybe breakage was an issue?

Rumor has it that the mod iron is the weak link in the KW-1 in stock
configuration, related to the splatter filter and (to a lesser
extent?) clipper circuits. I bypassed both in mine back in the early
90s, but lost the mod iron last year anyhow. More likely due to age at
this point.

Viking KW didn't use either of these circuits and supposedly didn't
have the issues of cooked mod iron that the KW-1 did. But time takes a
toll on the old insulation, wire or fish paper, worth keeping in mind.

Two things seem to come to the surface in my dealings with the KW-1:
the mod iron certainly can't be accused of being overbuilt and running
it at 100% likely approaches its limits; and a quad of 6B4Gs instead
of a pair would've worked better for driving it, especially at the
12,000 winding. Haven't looked inside the Viking KW for a while now,
but I think it only runs a pair also?

Skip, K7YOO has a lot of experience with these transmitters and
related iron, maybe he'll jump in.

~ Todd,  KA1KAQ


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