[tubeswell]

Pin 7 should be just a volt or so below the cathode (Pin 8) voltage for proper biasing. In the cathodyne stage, the cathode voltage should be around about 1/4 of HT voltage and the plate should be around about 3/4 of HT voltage. If the coupling cap supplying the cathodyne grid is leaky, then the DC can throw off the bias in the cathodyne, resulting in volume loss. Unsolder the grid-end of the cap from the board and clip your V-meter onto the loose end, and switch the amp on and check for DC (between the cap and the amps ground return). There shouldn't be any. (This will be a lot easier once you have put the board in the conventional way around).