Gordon,
I did use 6.3VDC in the scope. That is because I used a toroid transformer that has two 6V windings, not 6.3V. Under load, the 6VAC dropped a bit too much. The laminated transformer you use does not need to feed d-c to the heater. The 7.1V is Vnl which would be normal.
You eliminated the leakage from the focus pot to chassis by floating it. One less thing to wonder about and one more thing you know is not the problem.
Mark
