6146W Information:

[Glen Zook]

The 6146W was, until between 1964 and 1965 (depending
on the manufacturer) basically the same as the 6146
then the 6146A (which has the improved "dark heater"
per RCA).  After that date, the 6146W became the
equivalent of the 6146B.  It was due to this fact that
the 6146W became the 6146B equivalent that Collins
Radio had to redesign the neutralization circuitry in
the 32S3 and KWM-2 series equipment.  When the 6146B /
newer 6146W are used in those S-Lines with the older /
unmodified neutralization circuitry, the components in
that circuitry "burned up" on a very regular basis.

Thus, Collins had to change the circuitry in the newer
production and to come up with a modification kit for
those units already in the field to allow the use of
the 6146B / 6146W.  You can use the older 6146 and
6146A (also cross branded as the 8298) in circuits
that are designed for the 6146B without any fear of
neutralization problems.  However, you should only run
75 percent of the power input because the 6146 / 6146A
/ 8298 have only 75 percent of the power capabilities
of the 6146B / 8298A.

When the 6146B / 8298A (and the 6146W tubes
manufactured after 1964) are used in place of the 6146
/ 6146A / 8298 tube, then there is very often a
problem with neutralization resulting in all sorts of
problems.  If you want to try to use the 6146B / 8298A
/ post 1964 6146W tubes in place of the 6146 / 6146A /
8298, then you should try to neutralize them.  If they
won't neutralize, then replace them with the older
model tube.  If they do neutralize, then check them
for at least several hours, if not days.  If the
neutralization changes, then replace with the older
model tubes.  If the neutralization holds, then, in
that particular rig (not model of rig, but that
particular rig) it is OK to use the newer tubes.

This is due primarily to the differences in
interelectrode capacitances and the different bias and
screen voltage requirements of the 6146B family versus
the 6146 / 6146A family.  It seems that the 6146B is
much harder to "tame" than the older model tubes.
Thus, it takes more to neutralize them.  However, the
neutralization circuitry that does work on the 6146B
family fortunately works on the 6146 / 6146A family as
well.

You can mix the 6146 with 6146A/8298 tubes since the
primary difference between these tubes is the makeup
of the heater ("filament").  The 6146A/8298 have what
RCA called the "dark heater" which was more rugged and
performed better in a wider range of voltage than the
6146.  NEVER mix either a 6146 or 6146A/8298 with a
6146B/8298A.  That is really asking for trouble.

Electric Radio (the "boat anchor" magazine) published
an article on the use of the 6146 series tubes a
couple of years ago.  You can find the text of this
article and the illustrations on either of my websites

http://home.attbi.com/~k9sth

or

http://home.attbi.com/~zcomco

That article answers most of the questions about using
the 6146 family (including the 12 volt equivalents and
the 6293).  There is no problem with the copyright on
this article since I "know" the author quite well.

Glen, K9STH


--- Joe Cro N3IBX <Yardleyite at AOL.COM> wrote:

The W variant is an equivalent to a 6146A with a
ruggedized filament. If the application called for a
6146B you may not be able to neutralize the W's due to
different interelectrode capacitances.

=====
Glen, K9STH

Web sites

http://home.attbi.com/~k9sth
http://home.attbi.com/~zcomco

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