• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

12AU7 testing result: Are these tubes still good?

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Mrpong

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Joined 2004
#1
Firstly, for four ECC82 Miniwatt tubes, I conducted the emission test with Funke W19 and got these values

Tube #1 - 11.0/11.0mA
Tube #2 - 15.0/15.0mA
Tube #3 - 12/12mA
Tube #4 - 11.5/11.5mA

I don't know what we can tell from these results. Are they still good? or is it enough to conclude?

Secondly, can we select two match pair tubes from these four tubes? My guess would be tube #1 and #4. Correct?

Thank you.
 
#2
OK for life, I'd say. Few circuits actually run them that high.

Apply -9V to the grid, does the plate current nosedive on all of them fair equal? If so, they're good to go! 🙂

Secondly, can we select two match pair tubes from these four tubes? My guess would be tube #1 and #4. Correct?
Click to expand...

No. They have to be multi-point matched in their linear range.
 
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