[Drake] Matching 6JB6's with a Tube Tester

[Floyd Davidson]

"Mark NAce" <n5kae@swbell.net> wrote:
>Dear group, I have seen several folks mention that Drake finals
>can be matched using a good tube tester like a 6000A or TV.  I
>have also heard that Drake used to match their finals with a
>testing setup that used the same plate & screen voltages, bias,
>etc. as a working rig, by measuring the cathode current.  Does
>anyone have an opinion?  Thanks for your time Mark, N5KAE

The ideal way to do it would be a test setup that pulsed each
tube using the same element voltages as the transmitter does.
By pulsing the grid voltage, the balance at rated plate current
could be determined (without damaging the tube).  An ideal setup
might even be attached to a computer to record not just the
value at one point, but at many points for each tube.  Then the
computer could analyze the curves to determine which tubes
constitute a matched set.  Fun idea, but not really very
practical.

Has anyone ever modified any of the T4X varieties to have
separate bias adjustments for each tube?

I have this project in mind (and have acquired most of the
required equipment and parts) to convert a T4XB to use 6146B's
and provide each with a bias adjust and then see just how low
the IMD can be ajusted to.  Given that in the future 6JB6's are
going to be even more difficult to find than they are now, and
6146B/6146W/6293 tubes, not to mention newly manufactured
6146C's, are likely to continue to be available, that might
prove to be very interesting information.

-- 
Floyd L. Davidson           <http://web.newsguy.com/floyd_davidson>
Ukpeagvik "Place where people hunt snowy owls"     (Barrow, Alaska)