Best Tube Tester for 6SN7 & 6AS7

Hello Everyone,
Which brand and model of tube tester would work well for 6SN7 and 6AS 7 tubes? Also, what questions should I ask a seller to make certin that a tube testor is operating properly? Thanks in advance for your assistance.
Generally, there are 2 kinds of tube testers. The more-basic one tests for emissions, while the type that tests actual output measures 'transconductance'. Most manufacturers made both types; the emissions testers (ETs) were less expensive, smaller, and more portable, so there are a lot of them around. Most tubeheads prefer a transconductance type (TT), but each of those had limitations. I strongly recommend you buy a copy of Alan Douglas's 'Tube Testers and Classic Electronic Test Gear', still available new.

One meaningful limitation of TTs is that most if not all of them have a limited number of bias Voltages. If one of those Voltages isn't all suitable to the tube you're testing, the TT will test the tube for emissions. I think one question your should ask is whether the tester in question tests both your tubes for transconductance or for just emissions; the tube chart will indicate. FWIW my Mercury model 1000 tests both for transconductance.

One other requirement--don't even think about buying a tester without an operating manual AND a tube chart.

Good luck, and try to not get too frustrated in your quest.
You might try posting your question at the OTL Asylum, as both of these tube types are used in OTL amps so there's a good chance some of the people there will have experience with suitable tube testers.

I recently also made a decission on which tube tester to buy after reading and looking at multiable testers I decieded on a B&K 747B the reasons I choose this tester
1 easy to calibrate
2 lightweight
3 solid state no calibration tubes to buy
4 all different tube testers give readings in different values so you are looking not to match these values but to qualify the T.M.C. and tube life also look for shorts and grid emissions
5 but the real test is how do they sound I have tubes that do not test as well as others but outperform them in listening..
VacuTrace does this in real time:

It's the easiest way bar far to match sections within the tube. Also measures transconductance at any bias point.