AVO MkII: testing ECC81 valves

I found it hard to find any information about this venerable piece of valve history, so I finally got round to trying it out with a couple of ECC81 valves or 12AT7 for our American cousins.

I go through the procedure for testing this type of valve and compare one good valve and one which I rejected from the supplier. They are replacing it for me. It failed on my simple Knight Tube Tester which is an emissions tester - quite a basic test of a go or no go type.

However, this sophisticated beast duplicated the result and can also give transconductance measurements on top of that.

Hope it serves some purpose to someone!

More guitar related videos next!