[Johnson] Fw: Valiant Low Output

[Glen Zook]

The 6146 and the 6146A/8298 are identical except for
the fact that the 6146A/8298 has the "dark heater". 
The "dark heater" was designed for use in mobile
transmitters and the tube is designed to operate with
a larger variation in heater ("filament") voltage. 
You can even mix those tubes in an AC powered
transmitter without any problems.  But, NEVER mix an
earlier version with a 6146B series, that is
definitely asking for trouble.

The 6146B/8298A is a completely different tube and
many transmitters that were designed for the earlier
versions are just not "happy" with the later tube.  As
for 6146W tubes, prior to 1964 they were identical to
the 6146A.  When RCA came out with the 6146B series in
the first half of 1964 they originally stated that the
later tube was completely compatible with the earlier
versions and the military changed the specifications
of the 6146W to the new tube.  Unfortunately, this
compatibility did not "pan out".  However, the
military did not go back to the original
specifications.  Also, there is nothing on the tubes
that indicate which version they are except the code
date.  Also, each supplier of 6146W tubes changed the
specifications at a different time.  As such any 6146W
with a code date of 1965 or later is equivalent to the
6146B.  However, those tubes with a code date within
1964 can be either version depending on the
manufacturer and there is no known list of just when
each manufacturer changed from the 6146A to the 6146B.

For the article on the 6146 family of tubes that was
in Electric Radio a while back (and has been published
in several other publications since then) go to the
K9STH website (URL listed at the end of this message).
 Choose the K9STH link and then choose the article
from the list of links.

Glen, K9STH


--- John Lawson <jpl15 at panix.com> wrote:

Another 'gotcha' is to be sure you are using
'unlettered' 6146s - also most of the time "A"s will
work in the finals. "B"s are bad and in my (factory)
Valiant a brand new NOS set (expensive!) of 6146WAs
did this exact thing, only worse.










Glen, K9STH

Website:  http://k9sth.com


 
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