Im thinking of buying one for 120-135, id like to know if its a true mutual conductance tester, what frequency does it use to drive the tubes, what plate and bias voltages does it offer, does it have a short test late or an actual scale, is it all around decent or not so good, what would be a comparable tube tester. they guy just says it lights up so im taking a risk with it, but ive fixed a couple tube testers before and as long as its not the transformers ill be fine fixing it i think. Is there anywhere to get a schematic and manual? I cant find one yet. Any other info you know would be great thanks