Hi 6K is about right. The resistor was typically a big ceramic wire wound 10K variable.
No guarantee it's right for a clock, just that it's right for a teletype. Bob On Jan 22, 2012, at 5:46 PM, Jim Hickstein <[email protected]> wrote: > On 2012/01/22 15:29, Bob Camp wrote: >> Hi >> >> Teletype loop current as in 20 ma through the coil via a dropping resistor >> off of 125 vdc. > > Value for the dropping resistor? (I know, I'm an Extra, and I used to design > digital circuits, so I should know this stuff. But I've been in software for > a long time. Let's see.... E over I R.) > > I measured the setting coil at the terminals: 11.5 ohms. To limit 125 VDC to > 20mA, this would need an additional 6.2 Kohms. I suppose that represents the > metallic circuit back to WU plus a bunch of other 11.5-ohm clocks on the same > circuit, plus a compensating resistor back at the head end? > > Locally, a D cell (or 3 in series, which I have), with about 200 more ohms, > might do. (Reaches into desk drawer.) Let's see if I still have that bunch > of 100-ohm resistors left over from making an ISDN terminator. Why, yes! > Quarter-watt. P over I E. 90mW. Eh, it probably won't blow up. > > I tried measuring the winding coil, too: 0.1 ohms, but I'm not sure I was > getting it in the right place. And now I've put the face back on the clock. > Otherwise I couldn't tell what time it was! I am really trained to look at > that spot on the wall for this information. While the SWCC was in the > hospital (for over a year) I had to buy another clock to put there. The > blank spot was driving me crazy. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
