Search for the TSL60 schematic , it should include the heater wiring.
EDIT: there you have it:
Cluttered schematic, oh well.
They feed 6.3V AC "Fil 1 / 2" to Power and PI tubes, then rectify with a Bridge and 2 10000 x 6.3V capacitors, getting "Fil A / B" for the others, but the input tube seems to be fed through a flying wire (dotted line) and has its own extra 10000 x 6.3V filter.
IŽd pull the 6.3A fuse and measure AC current across the fuseholder terminals, without tubes and then inserting them one by one, until I find something unexpected.
Any AC consumption without tubes is abnormal.
Please post results.