tubes age 214
Jay KE6PPF
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Date: Sat, 21 Mar 2009 18:49:13 -0400
Subject: Re: [R-390] Current direction
>IIRC the supressor grid was to attract electrons that actually
>bounced off the plate and then impacted again causeing noise.This
>grid would draw off those errant electrons and thus improving the
>noise figure of the tube.
The suppressor grid is at a very negative potential with respect to both the
screen grid and the plate (generally cathode potential). Thus, it repels the
electrons that are re-emitted from the plate ("secondary emission"), sending
them back to the plate instead of letting them continue to the screen grid. This
is not done to reduce noise, but (1) to suppress the negative-resistance regime
of a tetrode, which causes the undesirable "tetrode kink" in the transfer
characteristic, and (2) to reduce the screen grid dissipation (mainly in power
pentodes).
Best regards, Don
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Date: Sun, 22 Mar 2009 11:38:20 -0500
Subject: Re: [R-390] Current Direction
Purdue University taught "conventional" (positive to negative) current flow while I
attended between 1968 and 1973. The Air Force taught "electron" (negative to
positive) current flow when I attended their basic electronics training at Keesler
AFB in 1973.
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Date: Sat, 04 Apr 2009 21:46:22 -0400
Subject: [R-390] TV-10 tube testing questions
I received my updated, calibrated TV-10 from Roger (alltubetester), and started
learning how to use it on the pile'o spare tubes I have collected for my R-390A.
As I understand it, the TV-10 is very similar to the TV-7, but the TV-10 displays
Mutual Conductance in Micromhos values directly. I have read that no two
testers will provide the same value for the same tube, so I understand that this
is not an exact science. But as I have no idea what to expect, I am asking for
advice as to if the values that I found from some preliminary testing are
reasonable or not. For all I know Roger may have put a small ravenous
Hamster inside the TV-10, and somehow attached it to the meter movement. I
(14 pages)
(10 pages)
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