6146 Replacement

[Kenneth G. Gordon]

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

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html