In my 8660C RF plugin, the output is present, but VERNIER
control cause about 40 dbm swing from max to min position.
Meter show just a 0,5 dbm swing, and needle is around
center scale.
I have already tried to replace some cards (A3,A10, ecc..)
taken from an worked unit, but with no success.
Is this a common fault for that unit?
Any suggestion?

Thanks.