[tbone]

In theory you could measure the resistance between the 6A8 and 6K7 grid caps. It will include the resistance of the IF secondary, but would take into consideration the whole RF coil secondary. An open anywhere in the multi tapped coil would show an open between the two points, which I chose because of easy access and less disturbance to the radio.

I would think the voltage should be identical on both grid caps, as there really is any grid current to speak of. Taking readings might affect the tuning of each circuit causing a change, but you get the idea.