How do other people go about keying B+ in their rigs? What I do, as it was setup in my rig, back in 1986, is that on the rear apron of the RF deck, is a tap for bias voltage. When sufficient drive is applied, the current from there to ground closes a contactor relay that closes at about the same grid current required by the 250TH's (45mA per, for a pair for a total of 90mA - and I run around 125mA to make sure the tubes are plenty cut-off for Class C) and when drive is applied, the relay closes and primary voltage (adjusted by a variac) is applied to the plate transformers.
What's another way? a relay to make/break the center-tap to ground connection in the primary of the plate transformers? 73 = Best Regards, -Geoff/W5OMR
