"N_Cook" wrote in message
...
No user switchable option. I can see its possible to rewire the vibrator
so
you still get right polarity for the anode supplies. Heaters presumably
happy enough powered the other way round but how to change the biasing of
the valves ?



Unless it's a synchronous vibrator, it should run equally well on either
polarity. The radio doesn't get anode voltage from the car's DC, it gets it
from the radio's DC-DC converter (vibrator, transformer, rectifier,
filtering).