Yes, there are diffences between the A and B versions. There are also
differences between various manufacturers. However, that doesn't change
the fact that the two tubes are generally interchangeable. All of the
hoopla got started when an article was written about some problems
Motorola had with some VHF gear that was designed around the 6146A and
had fixed neutralization. Their attempt to stadardize around the 6146B
caused them some problems.

The bottom line is, if it will neutralize, it will work fine. Frankly,
I've never found a piece of ham gear they won't work in. A partial list
of radios I have used them in with NO PROBLEMS:

COLLINS: KWM2A, 32S3A
GONSET: Commander
HEATHKIT: DX-60, DX100, HW-100, HW-101, Apache
JOHNSON: Ranger, Valiant, Viking II
KNIGHT: T-150
MULTI ELMAC: AF67, AF68
WRL: Globe Scout 680A

There are others. Like I said, I've never found an example where they
won't work, and work well. I haven't tried them on VHF equipment. I'll be
the first to admit that there could be a problem there.

Darrell






Darrell wrote:
Make sure that your replacement finals are 6146, or 6146A's, never

B's!



I've got to challenge this statement. This rumor has been circulating
for several years now. When I received my new HW-100 from Heathkit in
1968, it came with RCA 6146B's. There was a note enclosed that said
that they(Heath) were having problems getting 6146A's and that the
6146B's would work fine. They did. The radio neutralized without any
problems and stayed that way.

That there are big differences between the 6146(A), and the 6146B is
not a rumour. It shows up on the spec sheets as different
interelectrode capacitances. The 6146B had a bigger plate size, and
handled something like a third more plate dissipation.

It would have been better if I had said that you must use which ever
was certified by the manufacturer, straights, A's or B's.

Heath had already made the necessary modifications to the final
section of your radio. You would probably have had problems if you
tried A's.

The 6146B should have been issued a new number.

-Chuck