Replacing OA2 VR Tube with Zener Diode

[john w. king]

Has anyone replaced OA2 regulator tube with Zener diode especially in johnson ranger and Valiant transmitters and other VFOs such as heath and Johnson 122? If so how did you do it and what values of components did you use? What results did you get? Any info includint a diagram would be greatly appreciated. Can you refer me to an article treating that change? Thanks and 73, John, K5PGW