So I have 2 different ways I can do this I can use multiple Zener Diodes, mutliple resistor values and a common capacitor in the chain and just use a switch to select the right diode resistor combo to get the right bias that or close enough.....I like the simplicity of that idea and if something goes wrong you can trouble shoot it in about 30 seconds time. The other would be to use a transistor and associated partsto regulate the bias. THis method would provide the perfect bias at any power level so you would get slightly better power output, slightly longer tube life and less heat in the box. I am just not sure how reliable or durable this method would be. I already gave up my desire to use tube 1/2 or full wave rectifer's in series to do the ac-dc regulation. Basicly to get the current output I needed I would have to have used not less then 10-20 rectifer tubes in a combo of series and paralleled network to get tot he proper current and voltage. I would have had to power them up 1-2 or more minute at least before putting any high voltage through them and they would take up a lot of space and generate a lot of heat. I had questions that no one seemed to be able to answer about them as well.....I do not think you should parallel tube rectifiers but no one I asked could tell me for sure. So I changed my mind and now am going with modern silicone diode 1000V 6a, 450V 100uf Teflon Caps and balancing resistors mostly to bleed them down because I do not believe you need to balance this type of circuit with them to be honest.It is a rectifier doubler circuit. I have 23 of the above 100uf 450V caps to play with. I am using two of them to 2 of them int he case of 25 to repair a 10meter Linear. I know a lot of guys use 240uf 450V caps in their rectifier/doubler designs but I got a good price on the above. I hate changing my mind about design I am usually a very decisive and do not change my mind often but this is all knew stuff for me. I have repaired plenty of stuff but this is a combo of my idea's and other peoples idea and I find that my lack of experience creeps in and causes some doubt. So what do you guys and gals think should I stick to the simple idiot proof Zener bias control and use a switch to select my bias or should I go solid state? If I go solid state I will not need to babysit it at all it will be out of sight and out of mind.