You're making progress however, don't stop here or the tube won't like it. The -35 volts is where you want the 8417 bias in transmit. The -24 in receive is actually biasing the tube harder in RX. Bypass the existing bias contacts on the relay and connect those wires so the tube always sees the -35 volts of bias. Use the vacant relay contacts to turn the 350 volt screen voltage on in TX only, as Nomad suggests. This time proven method works well on these amps.
The main difference between the 6L6 and the 8417, are the bias levels in grid driven operation. Where -31 volts puts a 6L6 in class AB1, it puts a 8417 in class C. It only takes -12 volts to hold an 8417 in class AB1. The 6L6 needs more negative bias to run in the same class of operation as the 8417 and is why it runs better in the newer modulator with -56 volts in TX. "Modulators" tend to run these tubes closer to class C, in order to exaggerate forward swing on AM. It's also why they should sound funky on SSB, when running as a class C modulator.
The main difference between the 6L6 and the 8417, are the bias levels in grid driven operation. Where -31 volts puts a 6L6 in class AB1, it puts a 8417 in class C. It only takes -12 volts to hold an 8417 in class AB1. The 6L6 needs more negative bias to run in the same class of operation as the 8417 and is why it runs better in the newer modulator with -56 volts in TX. "Modulators" tend to run these tubes closer to class C, in order to exaggerate forward swing on AM. It's also why they should sound funky on SSB, when running as a class C modulator.
