Jules wrote:
On Fri, 09 Oct 2009 09:04:47 -0700, windcrest wrote:
I still have an old AC/DC radio from
those days, when radios were sold to work on either distribution
system.

Hmm, that triggered a memory. I used to have an AC/DC one from the '60s -
manual switch, and you could feed 12V DC in on the same power socket as
AC. I doubt something like that would pass H+S these days, never mind the
amount of people who'd try to feed it domestic AC with the switch on the
DC setting and fry the thing

cheers

Jules



That's actually a bit different. The AC/DC radios he refers to use a
transformerless power supply with the tube heaters wired in series.
Yours likely wires the tube heaters in parallel with a vibrator to
supply B+ to the plates when running from batteries.

The worst offenders for radios being plugged into the wrong voltage are
32V farm radios. The old 32VDC rural systems used the same plugs and
receptacles as the 110VAC systems standard elsewhere, so it's common for
someone unknowledgeable to plug a farm radio into a 120V receptacle and
blow all the tube heaters.