Ok. Let’s try this again…RCA 9TC240 Alignment

[Penthode]

I concur. The shunting of the coils with the 330 ohm resistors will mean the gain is reduced. You may try reducing the bias a tad with the rheostat. Also you may need to raise the signal a bit.

You want to ensure the curve does not appreciably change with signal level and bias change. That you can verify raising a lowering the signal a bit.