http://www.dynakitparts.com/dynakit-pro ... pgrade-KitThe schematic & parts values in its accompanying documentation appear to be the same as the bias control setup in the schematic for the diytube ST-35.
The plates in my EL84s were over-spec for power dissipation (>13W), and I could not get the bias current down low enough to compensate. Without changing any of the parts on the bias PCB, I have been able to shift the range of biasing downward by adjusting the resistor in the B+ supply. So, I changed the 50-ohm resistor, which dropped the B+ a bit while also enabling me to lower the bias current a bit, too.
Problem is, I like to roll different sets of EL84s, and changing the B+ resistor in this way then made it a very close call to get the bias up high enough for a different set of EL84s. While doing it this way enabled me to reduce the plate dissipation by a combination of lowering the B+ and also the bias current, the bias current is now running at less than 35mA (IIRC).
Is the bias current supposed to be running at 35mA for best performance, regardless of the level of the B+?
I was wondering if there might be a way to broaden the range of the bias adjustment overall, sufficiently upward or downward in order to set 35mA, even after lowering the B+.