rockstah wrote:Larry talk to me more about the 250k dual pot and the 2.2m resistors - not sure where they go
Ok - step by step:
- The coupling caps are connected to the input lug's of the pot
- The bias supply voltage (which usually feeds the both 220K) is connected to the output lug's of the pot (of course to both)
- The pot's wipers are connected to the power tube's grids (or to their swamp resistors)
- Now simply solder each a 2.2M on each section of the pot from the wiper to the output lug - a small 1/4W resistor will do it
These are only for safety, because if the pot's wiper fails, then the output tube's grid is w/o bias voltage and will immediately jump over the Jordan.
But with the resistor applied and a failing wiper, although this side can't be regulated anymore, but nevertheless there's bias voltage on the output's grid - and the tube(s) will survive
Larry