[Amps] Question: looking for a design for a simple test fixture for4-125A

Fuqua, Bill L wlfuqu00 at uky.edu
Wed May 11 22:19:15 PDT 2011


Anyone else going to Dayton?
73
Bill 
wa4lav at space 2905

________________________________________
From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of k7fm [k7fm at teleport.com]
Sent: Wednesday, May 11, 2011 11:37 PM
To: Robert Groh; amps at contesting.com
Subject: Re: [Amps] Question: looking for a design for a simple test fixture    for4-125A

"I just would love to find out if these tubes will work and pull current and
handle some voltage."

In the 1930's, hams did not have tube testers - so they tested each tube
manually by setting applying some voltages, measuring current, then
calculating gain of the tube.  You can actually some testing with a filament
transformer, a couple of analog or digital volt and current meters and a pot
(or vaiable voltage source.

Not long ago, I wanted to know if a big old 211 was any good.  I set up a
filament transformer, used a 9 volt battery for the plate supply, a
microammeter for a plate current meter, another voltmeter for the grid.
Then, I varied the grid voltage and logged the plate current change with a
change in grid voltage.  Surprisingly, the gain was calculated in the ball
park.

No, this will not test the tube under actual operating conditions - but at
least you will be able to compare one tube with another and see if you have
any real duds.  No, it is not like testing the tube on 6 meters.  But, you
have a crude tube tester with not much expenditure in time and no money.
Test the tube as a triode, strapping the screen to the plate.

The good news is that you do not have to worry about getting shocked.

73,  Colin  K7FM

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