15-11-2014, 12:12 PM
(This post was last modified: 15-11-2014, 12:15 PM by Old Sparky.)
What I found, some time ago, was that, with a full wave rectified o/p followed by a series pre-set resistor and a couple of 1N400x diodes in series across the o/p to ensure that the voltage applied to the filaments couldn't rise above 1.4v, that, if I set the 30 ohm pot. to give close to 1.4v the radio operated OK, but the load on the winding was too great, even after disconnecting the 12v LES bulb connected across the LT winding (part of the original Murphy Design) After all the 5 filaments in parallel draw 250mA, which is double what 5 filaments in a set fitted with '96' range valves consumes.
