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tube tester

3/26/1998 10:58 AM
tube tester
I am looking for schematics on how to build a tube tester Can anyone help?
3/26/1998 2:54 PM
Bob Holley

I have an instruction/construction manual  
for an Eico Model 625 Tube Tester,  
copyrighted 1952.
3/29/1998 8:28 AM

Dear Bruce: Exactly what type of tube tester are you looking for? Most commercial and military units were designed to minimally test receiving and low power transmitting tubes for radio and television. These units will perform their tests on a very wide variety of tubes.  
Are you looking for a tester for audio - primarily instrument amplification tubes? If so you need a limited number of socket arrangements and components. I use an old class A amplifier that I removed from a institutional (school) record player. I have an octal socket wired for the 7AC basing (6L6, etc, EL34 if pin 1 is tied to 8) and a 9 pin miniature socket wired for 9A basing (12A_7, etc). I also have one ohm, 1% resistors in the plate, screen, and cathode paths and a variable bias control from 16 to 70 volts. With this circuit I can insert the tube under test, check static characteristics by changind the bias and dynamic characteristics by sending a 1 kHz square wave down the signal path. Current draw and matching are measured using the one ohm resistors and clipping can be observed on a scope. Signal tubes can be tested for gain, noise, microphonics and "tone" (I use a known guitar, a known speaker, and a known output tube). By the way, this little amp with solid state rectification gives me about 490 volts of Ep and Eg2 and about 70 ma - I can push a EL34 to 11 watts. Not a full load tester obviously but a really quick way to sort out and match tubes.  
E-mail me and I'll send you a circuit diagram by snail mail.  
3/30/1998 12:41 AM
There was an article in Jan editon of "electronic world" which included plans for an output tube tester. It ran the tubes under a variety of conditions including under load etc,  

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