[Boatanchors] 6146B

[Glen Zook]

Collins used a ceramic trimmer in the neutralization
circuit in the earlier S-Line equipment, not a
compression trimmer.

It is just not amateur radio equipment that has
problems with the "B" series.  For example, in the
Motorola Motrac HHT series the "A" model through the
"D" model will have major problems when the 6883B (12
volt equivalent of the 6146B) is used.  The tubes will
definitely overheat due to spurious emissions.  In the
HHT "E" model, LHT, and MHT versions the transmitter
was designed for the 6883B / 8032A / 8552 and work
fine with the later tube.  However, to go back and try
to eliminate the problems with using the later tube in
the earlier models violates the type-acceptance of the
transmitter and therefore cannot be done if the unit
is used in the commercial services.

It is not even different models of transmitters in
which problems occur.  I have seen like 3 transmitters
of a particular model with serial numbers within 10 of
each other.  The "B" worked fine in 1 and not in the
other 2.

For a while Heath had specially selected 6146B tubes
that they supplied with the HW-101 and SB-102 that did
not have the problems that most "B" series tubes
exhibited.  I don't know just what the difference was
between these and the "normal" 6146B.

Anyway, there are those persons who have never had a
single problem using the 6146B in place of the earlier
versions and there are even more persons who have
definitely had problems.  There is no "obvious"
solution that does not require some modification to
the equipment (in some cases minor, in other cases
major).  It then becomes a question of just how much
effort the owmer of the transmitter wants to go
through just to be able to use the "B" series of
tubes.

Glen, K9STH



--- Garey Barrell <k4oah at mindspring.com> wrote:

I think the problem with the early Collins
transmitters was that they used a compression trimmer
for the neutralization. The trimmer cap "burned up"
because of RF current or ?.   The later transmitters
used a small air variable trimmer and works fine.

Glen, K9STH

Web sites

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

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