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The tetrode boards aren’t particularly complicated if you only implement the screen current trip. On my tetrode amplifier, I eliminated the control grid current trip and ALC circuitry. Their primary purpose is providing regulated screen voltage with most of the larger components placed off the boards. The schematic diagrams are still available on G3SEK’s website so spinning up an equivalent set of PCBs — perhaps just one PCB is all that’s needed — should not be difficult.

Mike WB2FKO

On Dec 27, 2024, at 9:03?PM, Billy Pickering via <pickeringw=[email protected]> wrote:

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Well, I was lucky enough to pick up a Henry Tempo 2006 that did not have any tubes. Yes, 3CX400A7 tubes are expensive so we were looking into modifying it to run 2 or 3 4CX250B tubes instead. I know we need to have screen power for these tubes, and was wondering if anyone was currently making the GM3SEK tetrode control boards. I guess we could come up with something from scratch, but those boards are really nice.

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I guess if it really come down to it, we could modify to run the single 3CX800A7 we have, but not sure if the tube is any good as it was pulled from a commercial unit.