[Boatanchors] 6146 question

[Peter Markavage]

Years ago  I received an Apache from a friend that had no 6146's
installed. I put in a new pair of GE 6146B's a had a problem with
neutralization just on 10 meters. Replacing the tested good 5763 driver
tube with another one solved the problem. On another Apache I worked on
which had 6146A's in it, the neutralization adjustment wire, which runs
up into the final tank compartment, had to be shortened by about  .75
inches in order to neutralize the rig. In rigs that don't provide an
neutralization adjustment, a wire stub a few inches long from the cold
end of the driver coil run up near the glass of both tubes sometimes will
provide you a means of neutralization. I seem to recall a CQ Ham Clinic
article piece that offered this as a suggestion  to a neutralization
issue on some rig (don't remember what rig or rigs they were discussing).

Pete, wa2cwa

On Wed, 14 Jul 2004 07:40:29 -0700 (PDT) Glen Zook <gzook at yahoo.com>
writes:
> Whether or not a 6146B / 8298A (or 6146W made after
> 1964) will work in a particular transmitter that was
> designed for the 6146 / 6146A / 8298 is a "crap
> shoot"!  Some rigs work fine with the 6146B series. 
> Other transmitters won't work worth a "flip".  I have
> seen transmitters that differ in serial number by less
> than 10 in which the 6146B would work in one of them
> and would not work in two of them!
> 
> I have worked on some Ranger I and II units that had
> the 6146B inserted.  Frankly, everyone of them decided
> to go "south" after a very short period of time.  I
> have worked on various Heath rigs that have had the
> 6146B series installed.  Some of them worked without
> problem but the majority of them did not!
> 
> It seems that the component tolerances, etc., seem to
> add in a particular direction that allows the "B"
> series to be used in one unit and not in another.
> 
> Collins had to modify the neutralization circuitry in
> the S-Line equipment in order to be able to use the
> "B" series (and the "W" series after 1964). 
> Otherwise, the neutralization capacitor "burned up" in
> at least 9 out of 10 transmitters.
> 
> One thing that I definitely do NOT recommend is mixing
> the earlier types with the "B" in an r.f. circuit.  I
> know that a few people have said that they have done
> this without any problems.  But, in the VAST majority
> of cases this is really asking for trouble!
> 
> In the DX-35 and DX-40, where the grid circuit is
> really loaded down (and the final is NOT neutralized
> in the original design) often you can "get away" with
> running the "B" series (and "W" with a code date of
> the 2nd half of 1964 or later).  But, sometimes this
> is not the case and the final tube will short out and
> sometimes take the transformer with it!  Since the
> transformers in this equipment is run at the "ragged
> edge" anyway, if the final melts down it often takes
> the transformer as well.
> 
> I suggest that if you have to use the "B" series (and
> "W" series) in a transmitter designed for the earlier
> versions that you neutralize the final and watch it
> closely for several days.  If the final will not
> neutralize then the "B" tubes should be immediately
> replaced with the earlier versions.  If the
> neutralization "drifts" then the "B" types should be
> replaced with the earlier versions.  If everything
> holds, then that particular transmitter is "happy"
> with the particular "B" tubes installed.  That is not
> to say that they next time "B" tubes are installed
> that they will work fine!  You still have to
> neutralize, watch, etc.
> 
> Sideband transmitters are affected by the "B" problem
> just like the AM/CW.
> 
> For those who haven't read the article on the 6146
> family of tubes, go to either of the websites that are
> listed at the end of this message.
> 
> Glen, K9STH
> 
> 
> --- Ray Friess <rayfri at highstream.net> wrote:
> > Glenn:
> > Understand the rules for substituting 6146 tubes
> > thanks to your article 
> > on the subject.  I have a question though...
> > How about in the older AM/CW Heath rigs, such as the
> > DX 40, DX 100 and 
> > the Apache ?    Adjusting
> > neutralization is not called for when replacing the
> > finals in those 
> > rigs...    Do the same 6146 rules apply as in
> > the sideband transmitters?    Could I use a 6146W in
> > those am/cw rigs 
> > without worrying about when the tubes
> > were made?
> > Ray  wa7itz
> 
> 
> =====
> Glen, K9STH
> 
> Web sites
> 
> http://home.comcast.net/~k9sth
> http://home.comcast.net/~zcomco
> 

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