RE: What do these numbers mean?

Tubes Asylum

Questions about tubes and gear that glows. FAQ

In Reply to: RE: What do these numbers mean? posted by Tom Bavis on October 22, 2021 at 08:32:35:

One additional thing to know - you can convert the TV-7 meter reading number to transconductance with some simple multiplication. All you do is read the meter and multiply it by a number based on the Range switch position. The result is the Gm reading:
Range B - multiply meter reading times 25

Range C - multiply meter reading times 50

Range D - multiply meter reading times 125

Range E - multiply meter reading times 250 - Note that the "E" range is only present on TV-7D machines.

There is also a "meter reading to Gm" conversion table in the TV-7 operators manual.
Of course, whatever limitations are present in the circuitry, calibration, etc. will reflect in the meter reading - but the conversion is simple math.
Also, when you are evaluating a tube based on how close the tube is to the minimum keep in mind that MANY tubes tend to test closer to the minimums than others do, even if the tube is brand new and healthy. Also some tubes tend to test WAY over their minimums.
And some tubes act up when tested in a TV-7 as well - such as the 6922 which tends to oscillate and give you false readings.
As I see it, using a tube tester effectively is a matter of your experience to a LARGE extent.
Edited to fix typos

Edits: 10/22/21 10/22/21

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Follow Ups Full Thread

Topic - What do these numbers mean? - Wernehawen 22:34:38 10/21/21 (8)

RE: What do these numbers mean? - Triode_Kingdom 08:48:27 10/22/21 (0)

RE: What do these numbers mean? - Tom Bavis 08:32:35 10/22/21 (2)

RE: What do these numbers mean? - Jim McShane 14:51:19 10/22/21 (1)

So True! - opalize 16:18:29 10/22/21 (0)

RE: What do these numbers mean? - Palustris 07:46:21 10/22/21 (0)

RE: What do these numbers mean? - andy evans 05:57:07 10/22/21 (2)

I use 65% rather than 60 ~ nt ~ - Byrd69 07:36:06 10/22/21 (0)

RE: What do these numbers mean? - Rocket_Powered 07:06:04 10/22/21 (0)

Follow Ups

RE: What do these numbers mean? - Jim McShane 14:51:19 10/22/21 (1)

So True! - opalize 16:18:29 10/22/21 (0)

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