Quartz Clock Movement Timing Adjustment Possible?

Discussion in 'Electric Horology' started by Cheezhead, Aug 17, 2012.

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  1. Cheezhead

    Cheezhead Registered User

    Dec 30, 2010
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    I just bought and installed a typical inexpensive plastic case and gear replacement quartz clock movement and installed it in a clock. It runs one second slow per day and I want better accuracy than that. Does anyone have a method to adjust a supposedly unadjustable quartz clock movement or is it possible to modify a quartz clock movement by wiring in a small adjustable potentiometer or a variable resistor?

    If neither is possible, does anyone have a source for an accurate quartz clock movement? I would be satisfied with + - one second per week or better.
     
  2. harold bain

    harold bain Registered User
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    You could go with an atomic clock movement that corrects with a signal from Colorado.
     
  3. Cheezhead

    Cheezhead Registered User

    Dec 30, 2010
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    Likely not possible but otherwise a good solution. The clock has a metal case that completely surrounds the movement with metal including the metal dial. It's a nice looking carriage clock.
     
  4. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Hi
    There is usually a trim capacitor near the crystal for
    fine adjustement.You'd need an accurate reference
    and an oscilloscope to adjust it, other wise you'd be chasing
    your tail.
    The trim capacitor can usually turn 360 degrees. One half would
    increase and the other half turn would decrease. Without some
    way to see what you were doing, you'd never know if you were
    increasing or decreasing the speed.
    You could try using a MicroSet but it wouldn't be as good because
    you'd need to use a pickup of some type and that would have
    slight errors.
    Tinker Dwight
     
  5. dAz57

    dAz57 Registered User

    Dec 7, 2011
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    I think you will find there are no trimmers used in the current crop of quartz movements, in fact there is no way of adjusting them, it's done and set at the factory and that's it, most people would not notice anyway if it was out a few seconds a week.

    I installed a stock movement in a marine case recently since the last one died after 12 months due to salt electrolysis, the new movement gained around 5 minutes a week, even if there was an adjustable trimmer that is well outside the adjustment range, so pulled that out and binned it, the replacement was inside a second a week when compared to an atomic internet clock.
     
  6. dAz57

    dAz57 Registered User

    Dec 7, 2011
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    short answer, no, what you get is what you get, manufacturers have not fitted adjustable trimmers to cheap quartz for quite a few years, this includes watch movements too, the adjustment is made at the factory and fixed.

    to make the quartz adjustable requires the quartz oscillator to run faster than 32,768Hz, then an adjustable capacitor (trimcap) is used to slow down the frequency of the quartz, it can only be slowed down, not speeded up since it cannot oscillate any faster than the shape it has been cut to.

    the other problem is the way the movement is adjusted, with no trimmer the makers do the adjustment at the divider circuit level, 32,768Hz is divided by 2 by 2 by 2 to get 16,368Hz, 8,192Hz, 4096Hz, 2048Hz until the signal comes out at 1Hz, the divider circuit can 'adjust' this 1Hz signal by 256 steps to the stepping motor,

    on movements made a few years ago there were a cluster of circuit tracks on one side of the chip which could be cut, one or more of these timing tracks were cut to adjust the rate of the movement, but the current lot of movements have no tracks so I can only think there is a write once eprom on the control chip that is burned in once and fixed, this is certainly the case with green circuit quartz watch movements from swatch.

    anyway the point is due to the fact the timing of the movement is done at the integrated circuit level adding a trimcap is not going to work like you would expect, the original quartz movements were simple, quartz oscillator, 32,768Hz running a bit faster than that, the divider outputs a 1Hz signal to the stepping motor circuit, the trim cap could adjust the movement to +/- 0.25 seconds per day.

    quartz crystals are temperature sensitive, with the older quartz watches they were adjusted to run 0.15seconds per day fast, once placed on the arm and the watch warms up it will lose 0.1seconds per day.

    so the clock will be affected by temperature too, slower in hot weather, faster in cold.

    so just to get better accuracy the quartz oscillator will have to be in a crystal oven at a controlled temperature, and maybe running at a higher frequency like 4.1MHz like some 1st gen quartz clock movements did.
     
  7. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Hi
    The temperature problem is that the crystals were really
    made for watches. They were cut to have a flat peak
    at right around wrist temperature.
    Sitting on a mantle, they are on a streep side slope
    of that curve.
    I'd not looked at newer clocks. It is a shame they no longer
    has a trim. I guess they make them as cheap as they can
    now.
    Tinker Dwight
     
  8. dAz57

    dAz57 Registered User

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    yep, and because they make make millions of watches it is cheaper to use a watch quartz oscillator for clocks.

    the trimmers have their own problems, apparently susceptible to moisture or humidity was one of the reasons they stopped using them in watches, with clocks it's just economics, the bean counters decided they could save 3 cents a movement by not using a trimmer.
     
  9. lmester

    lmester Registered User
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    I still find older quartz clocks with a trim cap at Goodwill, thrift and other used merchandise stores. Look for a hole in the back with a screw inside. This movement is made by the Rhythm watch co. My wife bought a quartz wall clock a few years ago at Walmart. She liked it because it matched the kitchen cabinets. It was not very accurate and it was a pain getting on a chair to reach it. I adjusted the trimmer carefully on one of my used movements and installed it. Problem solved!

    Also, I bought some new Takane brand movements from Ebay. So far all of the one's that I've used have kept good time. Much better than some of the cheap generic movements. Some of the Chinese movements are really poor.
     

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  10. harold bain

    harold bain Registered User
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    Luke, I've had good luck with the Takane movements, marked "made in USA". I mostly use the heavy duty c cell size movements. They aren't cheap, about $11. each. But, no callbacks.
     
  11. rievax_60

    rievax_60 Newbie

    Jan 24, 2014
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    Quartz clock movements usually run fast. I make a crude capacitor by tightly twisting to thin pieces of enameled wire together and soldering it across the crystal. I then gradually trim it until the speed is correct. I usually compare the stepper pulse to the one pulse per second output from a GPS receiver module.
     
  12. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    Radio hams used to make neutralizing capacitors
    that way.
    Tinker Dwight
     

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