Have you actually tried to 'beat' a watch. Most of these devices use a audio pickup and sense the mechanical impulse from the drive system. They then indicate whether the watch is fast or slow
I have one which uses the sound card to do the dsp and the secret sauce is the pickup and amplifier. Yes I work on clocks when I have time.... I would not assume the VCXO is out of spec unless you have a known good unit to compare against. Encouraging pirate manufacturers by buying their product is another topic for another time. If you had purchased a used unit you would have been able to get support for it. Sent from my iPhone On Feb 5, 2013, at 11:38 AM, john <[email protected]> wrote: > Hi Bill > > I've just checked - the oscillator does indeed go to the XTAL pins of the > Philips microcontroller. The crystal I thought was for the mc turns out to be > for the LCD display controller. > > I'll have a rummage for some resistors. > > Thanks > John > > > On Tue, 05 Feb 2013 05:20:48 -0800, WB6BNQ wrote: >> Hi John, >> >> OK ! It is good that the other resistors were there. It is also good that a >> lower EFC voltage lowers the frequency. >> >> I am not sure what standard values are available to you in the UK. I >> picked a >> standard value in the US that would roughly center the pot's range >> equally around >> 2.1 volts. >> >> So, I would suggest paralleling a 5.1K 1% metal film resistor across >> the lower 3K >> resistor. Attaching from the bottom of the pot to that resistor >> string's ground >> point would probably be easier then trying to attach directly across >> the SMT 3K >> resistor. >> >> The 5.1K added resistor puts the bottom resistance value at 1888.9 Ohms. The >> whole string would nominally be 5888.89 Ohms and ups the current in >> the string >> from 0.743 ma to 0.883 ma. A small change and should not be a problem as to >> power dissipation in the upper 3K. >> >> >> The voltage at the bottom of the pot should be near 1.67 volts and >> the top of the >> pot should be near 2.55 volts. That should place the range so that >> the VCXo goes >> below 18 MHz. If not then select the next lower standard value. Try >> to obtain >> 1% metal film at 1/8 watt or second best carbon film at the same >> ratings. Do not >> use the OLD carbon composition type resistors. >> >> As Bob points out and I also agree, if your unit looks like the type >> I saw on the >> web site, then the 18 MHz oscillator most likely runs the computer >> system. That >> does not necessarily mean it is also the clock that is clocking the >> A/D that is >> digitizing the sound. So, varying the 18 MHz may not change your >> results. The >> important clock, for accuracy, is the one that clocks the A/D inside >> your unit. >> >> Time will tell. After you add that resistor and then readjust the 18 >> MHz based >> upon your counter, you will know if the watch is on time the next >> day. If not >> then it will require further study of the circuitry. >> >> Good luck, >> >> Bill....WB6BNQ >> >> >> >>> _______________________________________________ >>> 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. _______________________________________________ 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.
