[Johnson] More Valiant Progress

[Glen Zook]

There are individual transmitters that will work fine
with the 6146B even though they were designed for the
earlier versions.  I have heard from numerous people
who have not had any problems.  However, the number of
transmitters that do have problems is much greater
than those that work fine and I have heard from a lot
more people as to this fact.  The 6146B generally
works fine in modulators like in the Valiant series.

If the transmitter will neutralize and hold the
neutralization then that transmitter is "happy" with
the 6146B.  I have actually run into 3 examples of the
same transmitter of which the serial numbers were
within 10 of each other.  In those transmitters 1 was
"happy" with the 6146B and the other 2 definitely were
not.

However, in 99.99% of the cases mixing a 6146B with
one of the earlier versions is usually asking for
problems.  You can mix a 6146 with a 6146A / 8298
without any problems because the difference is in the
construction of the heater.  But, the 6146B / 8298A is
a completely different tube.

When the 6146B was introduced in February of 1964 RCA
announced that it was completely compatible with the
earlier versions.  Unfortunately, this did not prove
to be the case.  That is why the military changed the
parameters for the 6146W from the 6146A to the 6146B. 
By the time that the problems with using the 6146B in
place of the 6146A were discovered the military had
both types on the shelves with the same nomenclature.

Collins found out that the 6146B would actually burn
up the neutralization capacitor in the vast majority
of KWM-2 series and 32S- series of transmitters. 
Since the military wanted to be able to use either
version in the same transmitter Collins had to change
the neutralization circuitry on the equipment coming
off of the production lines and come up with a
conversion kit for the older units in military
service.  You can tell if the unit either came off the
production line with the "new" neutralization
circuitry or was field converted very easily.  Just
look inside the final amplifier cage.  If there is a
ceramic variable on the chassis then this is the old
circuit and the 6146B series MUST not be used.  If it
is an air variable then it is fine to use the 6146B.

In any transmitter that was designed for the older
versions of the 6146 even if the 6146B works fine, you
still cannot normally use the higher power of the
6146B because the power supply generally cannot handle
the additional load.

A good replacement for the 6146 and 6146A / 8298 is
the 6293.  This is an original series 6146 that was
designed for pulse service and can take 1000 watts
input when used in pulse service.  Back in the late
1950s and well into the 1960s amateurs would give
their "eye teeth" for a set to use in their Rangers,
Valiants, DX-100s, Apaches, etc.

Again, numerous amateurs have not had any problems
with using the 6146B tube in units designed for the
earlier versios.  But, the number of amateurs that
have had problems greatly exceeds the number that have
not had problems.

Glen, K9STH


--- peter markavage <manualman at juno.com> wrote:

And yet, I've been running ECG 6146B's in my Valiant
since around 85, B's in my Apache since around 74 or
75, a B in my Ranger since 88. No unusual operating
anomalies throughout this time using this stuff other
then maybe an occasional glowing of the knobs. One of
my Valiants even used a mixture of A's and B's. Even
ran B's in my HT-32A.





Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco


	
		
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