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Nixie clock runs too slowly

Discussion in 'Troubleshooting and Repair' started by RobMendell, Mar 15, 2019.

  1. RobMendell

    RobMendell

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    Mar 15, 2019
    I am looking to get a nixie clock repaired. The clock itself is in great shape and the nixie tubes are all good (I got the clock on eBay), but it runs too slowly. I believe there is a bad potentiometer or something. There is an adjustable pot for the speed, but it is ineffective. The clock is this one: http://www.mapsevoli.com/. I live in Chicago. Any ideas on who can repair this? The manufacturer has been unresponsive for nearly a year, but before they went AWOL they suggested that a shop could repair it with a couple of hours of work. Thank you!
     
  2. Nanren888

    Nanren888

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    Nov 8, 2015
    Seems a similar post on allaboutcircuits.
    It appears to suggest that the thing you are turning is a capacitor trimmer, not a pot. They also seem to suggest that it's a type that multiple turns don't do what you might think. The trimmer may have only one turn, which means that it's a partial turn you need, as they say over on that other site.
    Is it the red thing next to the word "voltage" that you are adjusting?
     
  3. RobMendell

    RobMendell

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    Mar 15, 2019
    Yes, that's my post there, and yes, it's labeled C10 on the board. I have in the past made both small (at first) and large (after the smalls didn't seem to matter) changes, but may not have measured for a long enough time or made the proper adjustments. No setting seemed to slow or quicken the clock's "tick" rate usefully. The manufacturer of the clock says that if the screw in the trimmer/pot turns more than one full revolution the trimmer/pot is broken.
     
  4. BobK

    BobK

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    1,612
    Jan 5, 2010
    In some trim pots, the shaft rotates to slide plates that are like a semicircle across each other. In this case, turning it one full rotation brings it back to the initial setting an you can continue to do this forever. In another style, this is a screw that pushes one plate closer to another. In this type, the screw can be out so far that is is not even contacting the plate and it might be possible to turn it several rotations with nothing changing. However, if that is the case here, the capacitance would be at a minimum which means the clock would be running as fast as possible and could not be slowed down by screwing it down.

    Bob
     
  5. RobMendell

    RobMendell

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    Mar 15, 2019
    BobK, this might well be what's happened. Thank you. If this is the case, I would need to replace the trim pot, yes? And I'm not an engineer but a clock owner.
     
  6. duke37

    duke37

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    Jan 9, 2011
    You have not said how slow the clock is running. A capacitor trimmer is unlikelt to be able to shift the frquency more than 1% or so. If the deviation is more than this, then the crystal is not controlling the oscillator frequency.
    You may be able to hear the oscillator or its harmonics on a radio.
     
  7. RobMendell

    RobMendell

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    Mar 15, 2019
    I'm gaining about 2 seconds per day, roughly a minute per month.
     
  8. duke37

    duke37

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    700
    Jan 9, 2011
    Then you will need to measure over a day or more with the capacitor in various documented positions.
    You can get one second pulses from a GPS satellite to better accuracy than you require.
    Comparing the phase of the two one second pulses should enable you to set the capacitance in a reasonable time.
     
  9. RobMendell

    RobMendell

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    Mar 15, 2019
    That makes sense, yet as a clock owner, not an engineer, I wouldn't know how to do that myself.
     
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