I have always killed all the B+ voltages in all my transmitters during receive/stand-by. I think it's insane to do otherwise. For one thing, if they don't outright self oscillate, even the low-level stages may still generate white noise that interferes with reception. Secondly, it's too easy to forget about the voltages being on all the time and touch the wrong thing when working inside the transmitter, yet it's impossible to troubleshoot most problems with everything shut off, filaments and all. Thirdly, the unnecessary stress on components running with voltages on them (and current flowing through them) all the time inevitably shortens the life of tubes, resistors (particularly carbon), capacitors and other components. In the Gates, I simply added an extra DPST plate relay with contacts in series with the stock plate contactor relay contacts, one in the line to the low-voltage primary and the other to the high-voltage primary. The extra relay is energised only when the T/R switch is activated and the whole station is put in transmit mode. This relay is energised through the sequencer, the last one to come on and the first one to go off when switching from transmit to receive. What was originally the "plate on" switch on the transmitter now serves as a "ready" switch. With it "off", I can hit the station transmit switch and the exciter stages are turned on and I get grid drive, but without the HV plate supply being on. With the transmitter's "plate on" switch turned on, it goes into full transmit only when I hit the transmit switch on my station T/R relay system. I have heard of hams who leave their +3500 volt plate supplies on all the time, because of the difficulties of re-charging the HV filter caps each time they hit the transmit switch, but for me, no thanks. I'd install a soft-start or step-start system instead. When I'm not transmitting I want all the +HV dead.