Dynaco MK IV & AB, ultimate MK IVi upgrade kit, auto bias for tubes ECF82, 6U8, 6GH8, 6GH8, 6F2, ECF80

DYNACO MK4 Auto Bias 

All described in the manual pdf in the "Download" section

Preparation
• Disconnect relevant wires from the original PCB driver card-reference MARK IV & AB DIAGRAM • Disconnect the connecting wire at socket 8 between tubes V2 and V3. Pins1 a 8 on sockets V2 and V3 remain connected by wire. • Disconnect the wire from the slider of the BIAS potentiometer leading to the driver.
Construction and Connecting the Auto Bias Module
• Mount the Auto Bias board with the new driver. • Connect the ground point to terminal 1 on the driver. • Connect the input to the IN terminal on the driver. • Connect the heating tubes terminals on the driver board and connect in the tube V1 to pins 4 and 5. • Connect feedback wires to terminals 3 and 7 - g2 power tube to terminal 7 and secondary OT to terminal 3 on the driver. • Connect AC power 6.3V AB to terminals 4 and 5 on the driver board • Connect CATH terminal V1 on AB to pin 1 and 8 of socket V3 • Connect CATH terminal V2 on AB to pin 1 and 8 of socket V2 • Connect GRD terminal V1 on AB to terminal 11a on the driver board • Connect GRD terminal V2 on AB to terminal 11b on the driver board • Connect the BIAS terminal on AB to the anode of the bias source rectifier
Settings
• PP stage 2 x EL34, class AB1, ultralinear: Set bias for EL34 tube. The recommended anode current in the AB1 class is 42.5 mA. 42.5 = 425 / 10.
Adjust Uref = 425 mV (0.425 V) using the Trim pot on the Auto Bias Module.
Very Important!
• DO NOT re-adjust the trim pot once the AB-D-MK IVi module is installed and wired up. The whole idea is to set it ONCE and forget it !