4 AMPS for heaters, post 49*, seems a lot by later standards but as I understand it, that was common with side contact valves etc, pre-war, so maybe it wasn't so unusual when R1155's were being built
. That was a very detailed PSU analysis you carried out there Richard [miles above my comprehension] but unless I'm confused [very likely] you went back to basics in the end
. There was a bit of a "Holy Grail" aura around the PSU and the floating negative bias circuitry, at one time but others just seemed to turn up and sort it [and the set] without a second thought. I wonder how the OP is getting on?
Dave W