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Old July 9th 18, 02:43 PM posted to rec.radio.amateur.boatanchors
Scott Dorsey Scott Dorsey is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 774
Default Johnson Viking ll

In article t,
Ralph Mowery wrote:


I picked up an Johnson Viking ll transmittter at a hamfest yesteday. I
have the manual for it.

It has been modified in several ways with no docummnetation. One is
there are 2 voltage regulator tubes in series that connect to the large
power resistor with the slider contacts on it. Is there a published
modification for this ?


There are a LOT of modifications for these things out there. I don't know
most of them.

If this is attached to R13, it's likely a shunt regulator for the
bias for the modulator. That would be a smart idea and probably bring
the distortion on the modulator down quite a bit.

Another thing is on the 807 tube plates there is an added resistor of
about 25 ohms. It is similar to the paricitic supressor on the plates of
the 6146s but without the wire around it. This is the first time I have
seen resistors this way in audio circuits. I am mainly solid state,but
have worked some with tubes, but have not worked on many audio
amplifiers of any power.
What is the purpose of those two resistors ?


There is normally a 22 ohm resistor in series with each plate for stability
and to act as fuses to protect the transformer in the event the tubes fail
into shorts. These are original, not modifications. Notice also 100 ohm
resistors in series with the grids.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."