Hi I suspect the 18 MHz is simply the clock to a CPU chip. Cheap CPU + code is more cost effective than a bunch of random logic. If the gizmo works that, there's a "microphone" picking up the ticking and the CPU does DSP to figure out what's going on.
Bob On Feb 5, 2013, at 6:18 AM, john <j...@ic0n.org.uk> wrote: > Hi > > Some very good questions - thanks for the responses. No schematic (or > documentation of any description - Ebay purchase), but I've done some > dismantling and had a poke around with a multimeter. This is what I find: > > The power supply provides +5.2V and +/-6V. Strangely, the silkscreen on the > board power connector says +5V, +8V, -8V and -24V. The power supply has no > components or wires for this latter voltage, so that's a bit of a mystery. > The -24V rail disappears off into some components, so maybe it's an 'option' > on another model? Anyway, let's not get sidetracked. > > The 1k pot is sandwiched between two 3k resistors (surface mounted on the > back, so not immediately obvious). I get 0V - 2.2V - 3V - 5.2V, so only 0.8V > adjustment range. The lower the voltage, the lower the frequency, and vice > versa, so I could just short the resistor that's connected between ground and > the pot? > > Modern mechanical watches are relatively impervious to changes in temperature > - balance springs and balances are made from materials which are much better > in that regard than their carbon steel forbears, which required split > bi-metallic balances to compensate. > > I agree that 18MHz does seem an odd number. The counter can work with watches > that beat at 5, 5.5, 6, 7, 8 and 10Hz so you'd think it would relate to those > in some integer way. > > Regards > John > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
