Re: Ekco CR280 valve/tube car radio, 1950s

A factoid about synchronous vibrators - a radio using one is polarity-
sensitive. That is, if the radio is negative ground, you cannot run it
positive-ground. If you do, the power supply will generate "B-
negative" instead of B-plus, putting reverse polarity on the filters
(smoothers). But a radio using a tube rectifier will run OK on either
ground polarity. Most will even run on AC, but with some wierd 'beat'
effects with the mains frequency.

Now a synchronous vibrator *can* be used with opposite ground by
simply reversing the two transformer secondary leads that would
normally go to the plates of a tube rectifier.