[Leon Crampin]

If the rectifier fitted is an EZ40, a separate heater winding is not required as its Vh-k (pk) rating is 500V. Most sets using this rectifier employ a common heater winding with the receiving valves. I haven't checked the UU9 data sheet for h-k rating, but it is listed as an EZ40 equivalent. The EZ40 is electrically the same as an EZ80 - I've yet to see one of these fail h-k.

Murphy played very safe with the early all-glass rectifiers, hence the separate winding. Probably wise as their preferred supplier was Mazda....

Load your replacement transformer with the intended HT and LT loads and check the heater voltage and temperature rise. If the voltage is within 5% of 6.3 and you can hold the core after an hour's operation it will be OK. A further check would be to compare the weights of the two transformers.

Another option is to fit LED or 6.3V 0.1A dial lamps.

Leon.

You could save another 1/2A or so of heater current by using a 6V6 as an output valve - plug in replacement with some loss of gain. Purists might squirm...