AVO tube tester alignment

A call out to all the tube guys out there

I've just scored myself a AVO mkIII tube tester and i've got the operation manual. However i'm suspect about the calibration of the machine as i get consistantly low mA/V readings on most tubes i test. I'm after the checking and alignment info for the tester so i can verify if the unit itself is operating ok

I don't know the MK III, but my MKIV is made so that it really cannot go out of adjustment.

You may want to get/borrow a known-tested tube from someone with a known-working tester, and recheck for yourself.

And yes - many, many modern (specially chinese) tubes are substandard-emission directly from factory.

Jakob E.

The AVO CT160 service manual describes a procedure whereby you can prepare a standardized valve (CV491 or 12AU7) for checking the accuracy of your tester. The CT160 service manual is I think available at BAMA. I went through the exercise to check my CT160 and MKII, and then my Steve Bench designed RAT valve tester. I occaisionally check them and find that the RAT tester never wavers, the AVO's don't tolerate sloppy procedure (especially the CT160) and can return slightly varying results. I assume that this is because they are lab grade testers and need a bit of care and skill to operate.