26-02-2012, 03:29 PM
Hi Joe, that 70 volts wouldn't be that far off, looking at the thumbnail diag. you posted it looks as though the anode supply is taken from a potential divider between HT+ and HT - so that would put the mid point voltage at roughly half HT if I am reading it right (my eysight's not that good) before that section of the valve even begins to pass current. Making the grid of that section slightly -ve should more or less cut the valve off and the mid point voltage of the potential divider should then read (with a high impedance meter) approx half full HT if the resistors are ok.
Lawrence.
Lawrence.
