LEAVE the tubes in their sockets? when doing your input swr tests.? ?The tube's? grid to cathode C? is directly in parallel? with the C2? cap of each PI tuned input. (5.9 pf PER tube).?
If this is the 3 x tube amp, input Z? is? 220 /3 = 73.33 ohms.? ?You only require just one resistor that's close to 73 ohms...and temp wire it in between the grid + cathode of just ONE of the 3 x tubes? ( any tube, but just one tube).?
If it's the 4 x holer, it's just 220 / 4 =? 55 ohms.? ?Same deal.? ?55 ohms from grid to cathode of any one tube.?
You don't require a SA or anything other test gear.? ?The vna? or any other analyzer is all that's required.?
