Johnson Valiant Expertise Needed

[Glen Zook]

By any chance are you using either 6146B/8298A or
6146W tubes in the final?  Many transmitters designed
for the original 6146 are VERY unhappy with the 6146B
/ 6146W.  The 6146 or 6146A/8298 work well but the
6146B/8298A or 6146W tubes with a code date of 1964 or
later can cause problems.

Also, if you mix the 6146B/8298A or 6146W tubes with
the earlier versions you are really asking for
trouble.

For the article on the 6146 family of tubes that
appeared in Electric Radio a while back go to the
K9STH website ( http://k9sth.com ) and click on the
K9STH link.  The link to the article is under the
heading of "Articles".

Glen, K9STH


--- "hudlerb1 at netzero.com" <hudlerb1 at NETZERO.COM>
wrote:

Hi All, just trying to finish up a resto on my very
expensive Valiant. Lots of new parts and she's looking
good, but have run into some weird problems someone
may be able to help with. Loading into a 50 ohm dummy
load, the rig seems very unstable and certain settings
of the plate control and loading send it into
oscillations on 160 mtr or 80 mtr bands. Not so
noticeable on 20 or 15. I have done a neutralization
adjustment by disconnecting the plate and screen
voltages and using a RF probe in the antenna jack, I
can null very nicely. At a very low grid drive, the
scope on the output shows clean RF, and the controls
load smoothly, no erratic dips etc. When you bring the
drive upwards to a normal level, all kinds of crap end
up on the carrier and the plate dips erratically or
not at all....so it has parasitic oscillations or
something.









Glen, K9STH

Website:  http://k9sth.com


 
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