6146 Type Tubes

[Glen Zook]

You really need to use the same type of tubes in the
final.  It is possible to "mix" a 6146 with a 6146A
since the basic difference is in the heater (the "A"
version has what RCA called a "dark" heater which is
less sensitive to voltage variations).  However, to
mix either a 6146 or 6146A with a 6146B or 6146W made
after 1964 there quite often are problems.

The later KWM-2 series have the "modified"
neutralization network and will work fine with the
6146B tubes as well as the earlier versions.  The
reason that Collins had to make the chage was the fact
that the military changed over to the 6146B equivalent
6146W in mid-1964 and did not make any changes in the
nomenclature.  The military wanted to be able to use
any version of the 6146 family.

Also, there were a large number of 6146W tubes that
were bought by the military (from an "off brand"
manufacturer) that would barely make it to 1 MHz and
would not function even on the 80 meter band.  The
company had been "paid off" and went out of business
before those tubes got into the supply chain.  Those
6146W tubes work OK as modulators, but are not worth a
"darn" for r.f. service.  A number of those particular
tubes show up from time to time.  I know of an
individual amateur who got about 20 of these tubes a
year, or so, back.  None of them worked as r.f.
amplifiers.

The 8298 is the same tube as the 6146A and the 8298A
is the same tube as the 6146B.  RCA really should have
used a different designation for the 6146B since it
really is a different tube.  RCA also originally
advertised the 6146B / 8298A as being directly
interchangeable with the 6146 / 6146A / 8298.
Unfortunately, that did not turn out to be the case.

Sometimes you can "get away" with using the 6146B
tubes in the Heath equipment.  But, more often than
not they cause problems.

The advertisement that RCA used when the 6146B was
first introduced is on the two websites that are at
the end of this message as well as the article on the
6146 family of tubes.

The 6293 tube is a variant of the 6146 that was made
for 1 KW power input for pulse service.  Those tubes
work very well in place of the "normal" 6146 / 6146A
and last many times (like 5 to 10 times) longer than
the "normal" 6146 / 6146A.

Glen, K9STH


--- William Ward <spencer_4488 at MSN.COM> wrote:

I just checked the final tubes and discovered one is a
6146 and the other is a 6146W.

=====
Glen, K9STH

Web sites

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

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