[Boatanchors] 6146 vs 6146A vs 6146B or 6146W

[Glen Zook]

Of course, you are entitled to your opinion.  Also, I have stated many times, as well in the article, that many people have not had any problems using the 6146B/8298A in equipment designed for the older tubes.

However, I have, for several decades, worked on "boat anchor" equipment for others.  It has been my experience that using the 6146B/8298A in equipment designed for the 6146 or 6146A/8298 has resulted in problems considerably more than those which have not experienced problems.

Also, over the years, I have received a considerable amount of letters and E-Mail messages confirming my findings.

The characteristics of the 6146 and 6146A/8298 (and their 12 volt equivalents) were known for years and various manufacturers such as Collins and Motorola designed equipment based on those characteristics.  When the 6883B/8032A/8552 came out, Motorola redesigned their radios to use the new tubes.  Starting with the U43HHT-1100E, the equipment was designed with the known characteristics of the 6883B/8032A/8552 and later versions of the Motrac, the LHT and MHT series, used those tubes as well.

There were also problems in type accepted equipment made by General Electric and RCA when the 6146B/8298A was used.  Therefore, it was not "just" a Motorola or Collins question.  The equipment was designed with the known characteristics of the 6146A/8298 because the 6146B/8298A, with the changed characteristics, were years in the future.  Actually, Collins made significant changes in the neutralization circuit in terms of certain components and not just in the capacitor itself.  There were 2 other fixed capacitors and a resistor value that were changed significantly.

Collins redesigned the neutralization circuitry when problems started with the 6146B/8298A.

Collins, Motorola, and numerous other manufacturers cannot be criticized for their designs having problems with the newer tubes because those tubes did not exist when the equipment was designed and therefore the characteristics were completely unknown.  When the characteristics of the 6146B/8298A did become known the manufacturers altered the design of their equipment to meet the new characteristics.

The Heath Company acquired a "special" production run of 6146B/8298A marked tubes from General Electric which were actually 6146A/8298 that they included with the HW-101 kits shipped from the factory.  The instructions cautioned the kit builder to use ONLY the furnished tubes and NOT to use any other 6146B/8298A tube in the units.  The caution also said that the 6146 and 6146A/8298 tubes would work fine.  But, again, NOT to use any other 6146B/8298A tubes!  As such, Heath was well aware of the problems using the 6146B/8298A in equipment designed to use the earlier tubes.

No where do I absolutely tell people NOT to use the 6146B/8298A.  However, I do tell them to be cautious because in my experience, and the experience of others, using the newer tubes does cause problems.  In many cases the circuits can be modified to use the 6146B/8298A, some easily and some with more difficulty.  Whether or not to modify the equipment is left to the owner.  But, it is my definite position that someone using the 6146B/8298A in equipment designed for the earlier equipment must be made aware that using those tubes may definitely result in problems without modification, etc.  It is very easy to destroy the tubes unless the operator is very careful and with new 6146 family of tubes now costing over $25 per tube (from most Internet sources), destroying a pair can pose a significant amount of money for some operators.  To others, that is a "drop in the bucket".

Ever since the article was first published, there have been certain persons very critical of the content.  But, for every comment that I have received criticizing the article I have received at least 10 confirming it.

For those who have not read the article, it is available at the following URL:

http://k9sth.com/uploads/The_6146_Family_of_Tubes_1.pdf

Rather than accept someone else's opinion I suggest that the person read the article and make their own determination.

All that aside, the question arises as just why did RCA continue to produce both the 6146A/8298 at the same time as the 6146B/8298A?  Different production lines would have to be used because of different processes.  If there was not a difference in the performance in the tubes then there would have been absolutely no reason to continue with manufacturing both types.  RCA definitely advertised that the 6146B/8298A was completely compatible with the 6146A/8298 based on things like inter-electrode capacitance, etc.  Unfortunately, when the new tubes started being used in existing equipment, it was discovered that, in fact, in many applications the 6146B/8298A would not work properly in the equipment.  So, RCA had to continue to produce the 6146A/8298 simultaneously with the 6146B/8298.

Being like manufacturers like to maximize profits it is VERY unlikely that 2 production lines, each with definite "fixed costs", would be run at the same time.

Again, I do caution people to be careful when using the 6146B/8298A in the earlier equipment.  Frankly, it doesn't make a "hill of beans" difference to me personally if someone destroys their final amplifier tubes, if they experience "strange problems", and so forth, because they are not aware that there are real differences in the tubes and those differences definitely can cause problems.  It doesn't cost me one cent either way.  However, on a "broader scale", I really don't want someone to experience frustration because they were not aware that using the 6146B/8298A in equipment designed for the earlier versions are likely to cause problems more often than not.

Glen, K9STH

Website:  http://k9sth.com


--- On Tue, 7/5/11, lee <pulsarxp at embarqmail.com> wrote:

Yes, this is the article I am referring to, Glen and others.  That said, maybe Motorola had a problem a zillion years ago because their neutralization was fixed in their VHF rigs.  Maybe Collins had a problem with too marginal a neutralization cap in their earlier rigs so they put in a larger more beefy neutralization cap which should have been there in the first place, even when they used 6146A tubes.  I don't dispute much of what is written there.
 
However, that article has put fear in many a ham when wanting to put B tubes within Heath, Johnson, WRL, type HF gear.  As I said,  I have done a lot of it and so has a friend of mine in HF ham gear, not in Motorola VHF gear.  I don't know anything about Motorola VHF problems, nor do I care to know about them.  I am only concerned with ham HF gear.  We have never experienced a problem with the B or W tubes.   That is why I asked for members on here to reflect their actual findings and not always referring to this publication I find has no bearing for hams wanting to re tube their old HF ham equipment. I have been receiving a lot of "private" E-MAIL telling me the very exact thing.  NO PROBLEM. Anyone on here ever have a problem using B tubes in their old Heath or Johnson type equipment?
 
I highly suggest list members find out for themselves what can really be put into your old ham HF gear and forget that misleading Motorola VHF article. Don't take my word for it.  Try them out and you decide what is correct. I find the article has no merit for ham HF equipment. There is no neutralization problem either.  I don't think publicized spec sheets lie either.  If they don't tell the full story, what good are tube spec sheets, when picking out what tubes could be used in a design?
 
The bottom line is, when you are restoring an old boat anchor ham HF transmitter,  using B or W tubes within it should be the least of your worries and concerns.
 
For you Glen,  I am truly not trying to pick a fight with you.  I understand your background and experience and what problems Motorola has had in the past with their fixed neutralized VHF gear, and also the neutralization cap change in Collins S-line gear.  I just think the background in your article has no real bearing when using B tubes in our old ham HF gear based on my real world experience when using these tubes.  A ham not knowing better after reading your article will many times avoid using a 6146B or W tubes when he needs to re tube his old HF ham gear.  I think that fear is misguided and the record should be corrected.