I have recently completed re-construction of an st-70 using the VTA board. After replacing an output transformer (you were absolutely right Bob...thank you) I have the 1st of 2 amps up and running in my system. Bias adjustment is simple and quick and my redings have been rock solid. The amp sounds fabulous! The only other thing I need to do is adjust the AC balance, but I have no idea how to do it. I remember reading about it somewhere, but cannot find the procedure anywhere. I seem to remember someone saying it was possible to make this adjustment without a scope and would at least get close. I have a friend who has a scope but have not asked him about it yet.
On a side note, I have to say this amp sounds better than I thought it would. It is driving the midrange section of my homebrew speakers which are open baffle line arrays. The midrange lines came out to about 5.5ohms and are running off of the 4ohm taps. The fresh st-70 makes the temporary tweeter amp sound like absolute garbage. A VERY happy customer here!