Philco gives no plate voltage for the 6J5 because the voltage chart refers to use of a tester
with a 1000 ohms/volt rating. Using that kind of meter, no voltage would show.
Also measuring the voltage would inhibit operation of the AVC circuit.
When you touched the 6J5 plate with your meter probe, you detuned the
circuit slightly , and your DVM picked up the voltage. Was the voltage
positive or negative ?
Does the shadow meter work in the radio ?