I've built a basic valve tester. http://www.valveheaven.com/2015/03/a...vetube-tester/ and http://www.valveheaven.com/wp-conten...lve-tester.pdf
It will test for shorts and gas leaks. The anode voltage can be set at 100/125/150/200/250/300v (more or less). The grid voltage can be varied. The anode current can be read. Basic matching can be carried out (anode current at typical grid voltages).
But the designer says that it will " Provide Gm or mutual conductance readings, directly or indirectly". So how do I go about this? If needed I could add other meters. I admit my constructional abilities outstrip my technical knowledge, but is there a primer or idiot's guide that will walk me through this? I have Morgan Jones' Valve Amplifiers and Building Valve Amplifiers (although I haven't got very far into the first one yet), so is all the info I need in there? Valve data sheets are all very well, but I don't (yet, if ever!) understand them.
As I get older (67 now) my brain is slowing and my memory is going, so I need to start simply. Or just need help! Any of which would be appreciated.