6146 Replacement

[Mike]

I too was a believer that a 6146 is a 6146 so what's the big deal? However,
after reading the article about the differences in 6146 tubes, I immediately
adopted the concept of "If the final was designed and built prior to 64, the
final gets 6146As". It's simply not worth the risk. For me it's a no brainer.

73's,

Mike
W5RKL



On Sat, 30 Sep 2006 16:41:04 -0700, Kenneth G. Gordon
<kgordon2006 at VERIZON.NET> wrote:

>On 30 Sep 2006 at 14:20, Bill Coleman wrote:
>
>> Here's the definitive article on this:
>> http://www.members.tripod.com/NRWILLIAMSON/t6146.txt
>
>In Glen's article referenced above, he says that to his knowledge,
>Heathkit never mentioned using the 6146A over the 6146B.
>
>However, on the back of my recently restored HW-101, there is a
>sticker which obviously came with the kit that says something very
>close to, "Use 6146A type tubes ONLY in this transmitter"
>
>Now, when I restored this HW-101, one of the original 6146s developed
>some sort of interesting internal short that burnt out the 0.22 ohm
>cathode metering shunt.
>
>At the time, all I had was a pair of NIB 6146Bs, so, with much fear and
>trepidation, I installed them, and VERY carefully neutralized the rig.
>
>Checking that over several days of operation, everything seemed to be
>stable and the rig works very well.
>
>However, I recently discovered that when I tune the rig up on 40
>meters, the GFCI associated with our basement refrigerator ALWAYS
>trips.
>
>Furthermore, I also recently discovered that with the outer cabinet off,
>on 40 meters only, under certain conditions the final oscillates and
>draws excessive plate current.
>
>Thus, as soon as I can obtain a set of 6146As, the 6146Bs will be,
>forthwith, removed and the "As" installed in their places. Then I will
>neutralize the rig as I did before.
>
>I thank Glen Zook for his valuable information. In the case of the DX-35
>or DX-40, this may not be a problem, since, as Bill Coleman mentions
>they are running in Class C. Also, the grid circuits of those rigs are
>purposely designed to be low impedance and this also contributes to
>those rig's stability.
>
>However, one must be careful and watchful if one has to use a 6146B
>where a 6146/6146A was original equipment, and if anything "funny"
>appears, go to the older tube.
>
>Ken W7EKB
>
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for losses or misrepresentations of any kind.  Buyer beware!

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