Install the M0UKD safety HT fuse mod to your 811A. 800mA fuse and 10W 15R resistor See u-tube. Then get some decent valves and remove the grid R&C and earth the grids directly to ground at the valve base with a nut and bolt terminal fixing. This is a grounded grid AB2 amplifier so ground the grids. If there are gas discharge devices installed on the heater lines then see if they are 160 Volt. If not then fit 160 Volt ones. Take all the precautions....Unplug from the mains. Wait for the bleed resistors to discharge the Caps in the PSU. Monitor on the HV plate meter. Fit a croc clipped service safety lead from Earth to one of the wires on a valve cap to be sure. Now the amp will work well. Good luck. MIKE. 73
Install the M0UKD safety HT fuse mod to your 811A. 800mA fuse and 10W 15R resistor See u-tube. Then get some decent valves and remove the grid R&C and earth the grids directly to ground at the valve base with a nut and bolt terminal fixing. This is a grounded grid AB2 amplifier so ground the grids. If there are gas discharge devices installed on the heater lines then see if they are 160 Volt. If not then fit 160 Volt ones. Take all the precautions....Unplug from the mains. Wait for the bleed resistors to discharge the Caps in the PSU. Monitor on the HV plate meter. Fit a croc clipped service safety lead from Earth to one of the wires on a valve cap to be sure. Now the amp will work well. Good luck. MIKE. 73