> Mike Morris <wa6i...@...> wrote: > And actually the DC distribution system was more common > than you think.
So is live steam... In large cities like San Francisco you can still find utility supplied DC and steam. Most of the Hydro Plants I've ever worked in were operated off/from a very large bank of series connected station size lead-acid batteries. The plant can start under its own 120 Vdc bank of batteries if the grid source is unavailable. There's a lot of DC and Steam still out there... > I recently was up at the Mt. Wilson observatory and was > inside the 100-inch telescope dome. ALL of the controls > for the telescope, the dome slit motors (the ones that > slide the panel open the telescope to look through), the > dome rotation motor (which is surprisingly small for the > load), everything but the overhead lighting is 120v DC. > And has been since about 1918. > Even the ballast tubes for the control are original carbon > filament bulbs. > I have alot of photos/ > Mike WA6ILQ > > At 02:13 AM 08/24/10, you wrote: > > >We had our fill of those here, too. The "hot" side of the AC line > >(if you were lucky, polarized plugs were rare in those days) was > >connected directly to a 35W4 or some such half wave rectifier tube > >and later to a selenium half wave rectifier with the other side of > >the AC line being connected as the negative lead (fortunately NOT to > >the chassis). Usually, there were a couple of 0.01uf capacitors > >from each side of the line to the chassis, however. Doubt I need to > >explain the joys one could experience with that arrangement! And, > >to top it off, each and every one of those radios proudly bore our > >UL stamp of approval! They used to call them AC/DC radios because, > >if you lucked out and got the polarity right, the radio didn't care > >what the source was as long as it was somewhere near 100 volts DC or RMS. > >Tom > > > >--- In Repeater-Builder@yahoogroups.com, Gordon Cooper <zl1kl@> wrote: > > > > > > Another quirk. > > > > > > > > > Sixty plus years ago in England, power factor was not > > > the main concern. Many of the domestic radio receivers > > > were transformerless and used half-wave rectification to > > > obtain D.C. for the tubes. A consequence was a fair dose > > > of D.C. flowing in the street power mains. > > > > > > Gordon ZL1KL > > > Tauranga N.Z. > > > > > > > > > > > > >------------------------------------ > > > > > > > >Yahoo! Groups Links > > > > > > >
