[Kenwood] 6146 Line of Tubes

[Peter A Markavage]

And here's Glen's, K9STH, additional comments concerning the 6146 series
of tubes and some history insight.
Pete, WA2CWA

On Sun, 25 Apr 2004 08:52:33 -0700 (PDT) Glen Zook <gzook@yahoo.com>
writes:
> Most equipment manufactured for using the 6146 / 6146A
> tubes are not "happy" with the "B" series of tubes. 
> However, I definitely have seen equipment designed for
> the earlier tubes that work fine with the "B" series. 
> But, I have also seen transmitters of the same model
> that differed by less than 10 in their serial numbers
> in which 1 worked fine with the "B" series and 2
> didn't like them at all!
> 
> Also, myself, and numerous others, have run into
> problems when "mixing" the earlier series tubes with
> the "B" versions.  Usually, this results in
> instability in the operation of the transmitter.  Not
> always, but considerably more often than not.
> 
> I learned many years ago not to make the statement
> that something "always" happens when dealing with
> amateur radio equipment!  There always seems to be a
> situation that "proves" the possibility of what you
> say "cannot" happen actually does happen.  But, in
> generalities, my experience has been such that you
> don't want to "mix" the earlier versions with the "B"
> versions.
> 
> Although I am not a "member" of the Kenwood list
> (don't want to be - don't have any Kennwood except a
> TR-7850 2 meter FM rig!), I keep getting asked for
> information on the discussion.  Therefore, I'll list
> my latest reply here on the Glowbugs forum.
> 
> The 6146B was introduced in 1963.  The last RCA
> specification sheet on the 6146B was printed in
> February 1964!
> 
> As for using "matched" pairs:  The manufacturers never
> installed "matched" pairs in the radios from the
> factory!  Even if you install matched pairs within
> several hours of operation the pair will no longer be
> "matched" since each tube "ages" at its own rate.
> 
> The only place that using "matched" pairs will make
> any difference that might even be noticed is when the
> tubes are used in push-pull like in audio amplifiers
> (and that difference is usually very little when "new"
> tubes are installed).  When used in parallel, you
> can't tell the difference!  All that "matching" does
> is to add to the cost of the tubes.
> 
> It will not hurt anything to use matched pair tubes! 
> Again, that, in my opinion, only adds to the cost!
> 
> As for the 6146W tubes being changed:  I have no idea
> as to why the military did not change the
> nomenclature.  Unless, this was due to the fact that
> RCA originally indicated on the specification sheets
> "The 6146B/8298A is unilaterally interchange-able with
> the 6146, 6146A, and 8298".  This "fact" was
> universally accepted by all of the major amateur radio
> equipment manfuacturers.  However, it soon proved not
> to be true!
> 
> By allowing the production change to be made, and
> since RCA had stated that the 6146B was completely
> compatible with the earlier versions, the military
> would have eliminated the need for stocking two
> different part numbers.  The "later" versions were
> only an "improved" version and thus wouldn't require a
> change in nomenclature.  The "newer" versions could be
> used in situations where the equipment had been
> designed for the 6146B as well as that equipment that
> had been designed for the 6146/6146A.  In my mind,
> this makes perfect sense (although the military
> doesn't always make sense in some of the things that
> they do when it comes to supply!).
> 
> If what RCA stated was true, why did Collins Radio
> Company have to modify the neutralization circuitry of
> those S-Line and KWM-2 series units that had been
> previously sold to the United States military
> organizations to be able to work with the "new" 6146W
> tubes (they had been perfectly compatible with the
> "old" 6146W tubes) and why did they change the
> circuitry in all new S-Line and KWM-2 series equipment
> that was produced?  The answer is obvious!  Their
> equipment had to be compatible with the tubes that
> were then becoming the "standard" for the military. 
> Since the nomenclature on the 6146W tubes had NOT been
> changed (for whatever reason it was NOT changed!)
> Collins had to make sure that their equipment would
> continue to function properly with the latest tubes!
> 
> Motorola eventually got "caught up" with the 6146B
> problem.  However, this was on the 12 volt heater
> equivalents.  In the mid-1970s someone at Motorola got
> the "idea" of furnishing the 6883B/8032A/8552 tubes in
> place of the older 6883A/8032 tubes that had been used
> in the Motrac series equipment since the very first
> HHT "A" models came out in 1957.  This was the result
> of a new company policy to reduce the number of items
> in stock at the Schamburg, Illinois, parts warehouse.
> 
> Motorola started shipping the 8552 tubes in boxes
> marked 8032.  At that time, I owned the Motorola
> reconditioned equipment center for the south-central
> United States.  We went through an average of about
> 100 8032 tubes per week, and, within a week, or two,
> we were having to use the 8552 tubes that were sent in
> the 8032 boxes.  Within a week of our starting to use
> the 8552 tubes in place of the 8032 tubes, we started
> getting all sorts of complaints about Motracs being
> received with broken tubes!
> 
> Prior to that we had not had a single complaint about
> broken tubes from shipping.  As a result, I started
> checking.  What was happening is that the 8552 tubes,
> when used in equipment designed for the 8032 tubes,
> were putting out so many parasitic emissions that the
> tubes were severely overheating in just the time that
> it took to tune up the transmitters and to do the
> final tests.  The Motrac is built such that you must
> have the final shield (which is also the heatsink for
> the driver and final tubes in the unit) in place
> before you can tune the radio.  As such, you cannot
> see the tube.  Otherwise, we would have immediately
> noticed that the tubes were severely overheating.
> 
> What was happening is that the tubes became so hot
> that the glass envelope was annealed.  The "normal"
> shipping "bumps", drops, etc., were such that the
> greatly weakened glass was shattered!  Even if the
> tubes survived shipping, they were being damaged
> within a day, or two, of being installed in the
> vehicle and then subjected to the vibrations of the
> automobile, truck, etc.
> 
> Motorola at first refused to believe me saying that we
> must have gotten a "bad" bunch of tubes.  However,
> within 2 weeks they got over 1,000 similar complaints
> from their field service stations about exactly the
> same thing.  The result was that Motorola had to get
> in an "emergency" shipment of the 8032 tubes, rebox
> all of the 8552 tubes that they had originally boxed
> as 8032 tubes, and they had to pay many thousands of
> dollars in warranty claims to their service stations. 
> All of this because Motorola "believed" RCA when RCA
> said that the "B" series of tubes were completely
> compatible with the "A" series.
> 
> Again, I don't have any problems with installing a
> "matched" pair of 6146B tubes when the equipment was
> designed for the 6146B.  It adds an unnecessary amount
> to the cost, but definitely doesn't hurt anything!  If
> the person doesn't want to use 6146W tubes made after
> 1964, then that doesn't bother me at all even though
> the tubes are the same (except the 6146W is "supposed"
> to be more "rugged" in its construction - but, the
> 8298A is also of the same "rugged" constructions and
> all RCA 6146B tubes are "cross-branded" with
> 6146B/8298A and thus should be the same as the later
> 6146W - this is not true of all other brands, they are
> not all "cross-branded"!).
> 
> However, I do take "exception" to the statement that
> the 6146B was not introduced until 1973!  It was
> introduced a full decade before!  In fact, you can
> even see the 6146B being "hyped" by RCA in all sorts
> of advertisements in the 1964 amateur radio magazines
> including the back covers of QST!
> 
> Anyway, there are always seems to be "exceptions" to
> any statement that someone makes about tubes,
> equipment, etc.  However, in general, I stand by my
> article, comments, etc., on the 6146 family of tubes. 
> Yes, under certain circumstances something else might
> happen.  But, most of the time, you shouldn't mix a
> 6146B (or 6146W made after 1964) with the earlier
> versons.  You should be very careful when substituting
> the 6146B (or later 6146W) in a rig designed for the
> 6146 / 6146A.
> 
> Glen, K9STH
> 
> 
> --- Peter A Markavage <pmarkavage@juno.com> wrote:
> 
> my Valiant has been running two 6146A's (not quite
> sure if they're both A's since I wiped the number off
> of it years ago) and 1 6146B in the final for the last
> 15 years. My Apache runs a pair of 6146B's. The TS-830
> has 1 S2001A and 1 6146 A running in it for the last
> 10 years. All perform well on all bands including 10
> meters. Closely matched tubes are generally the rule
> of thumb but I never learned that rule.
> 
> 
> =====
> Glen, K9STH
> 
> Web sites
> 
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