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Old 28th Jul 2019, 5:25 pm   #1
MeerKat
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Default Metamec Kundo Quartz clock capacitor

Hi All,

Our clock has died, it's the capacitor gone, I suspected it as there was a wave form across it. Took it out and metered it, it seemed OK but a replacement has got the clock going again, see pics, the grey one is the original, the blue cap is the test one, now I notice that when metered the voltage polarity across the capacitor changes on a regular basis in time with the tick. I'm pretty sure it should be a non-polarized one, especially as there are no polarity markings on the original, can anybody confirm?
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Old 28th Jul 2019, 5:38 pm   #2
TonyDuell
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Default Re: Metamec Kundo Quartz clock capacitor

A lot of these quartz clock movements apply a pulse to the coil of one polarity, then a second later a pulse of the opposite polarity, the next second one of the original polarity, and so on. The motor stator (coil core) is designed so that the (magnetised) rotor is pulled into alignment with the field from the coil when the coil is energised, then it rotates a little more when the coil is turned off to come into a stable position between 'tabs' on the pole piece area of the core. And then the next pulse moves it on in the same direction, and so on.

If this capacitor has anything to do with the signal going to the coil, it might well be a non-polarized one. Have you tried a pair of 100uF capacitors (same brand, same age if you can do it) in inverse series?

Incidentally based on the first paragraph, the direction the motor turns is determined by the asymmetry of the stator core in the pole piece area. With some of these movements (the modern cheap ones you can get almost anywhere, for example) you can turn the core over and reassmble the movement (there may be a plastic peg you have to shave off to allow it to fit, that was there to ensure it was correctly assembled at the factory). The result is a clock that runs anticlockwise.
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Old 28th Jul 2019, 5:46 pm   #3
usradcoll1
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Default Re: Metamec Kundo Quartz clock capacitor

Quote:
Originally Posted by Andrew64 View Post
Hi All,

Our clock has died, it's the capacitor gone, I suspected it as there was a wave form across it. Took it out and metered it, it seemed OK but a replacement has got the clock going again, see pics, the grey one is the original, the blue cap is the test one, now I notice that when metered the voltage polarity across the capacitor changes on a regular basis in time with the tick. I'm pretty sure it should be a non-polarized one, especially as there are no polarity markings on the original, can anybody confirm?
IIRC, the BP stands for Bi-Polarized, which is non-polarized.
Dave
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Old 28th Jul 2019, 5:47 pm   #4
Paul JD
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Default Re: Metamec Kundo Quartz clock capacitor

Yes, that is a non-polarised cap (the BP marking on it refers to bi-polar which a lesser used name for non-polarised capacitors). You might struggle to find a 56uF replacement but I would imagine a 47uF should work.

Edit: post crossed with above
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Old 28th Jul 2019, 11:24 pm   #5
MeerKat
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Default Re: Metamec Kundo Quartz clock capacitor

Thanks for replies and the detail Tony, the capacitor I tested with is an electrolytic so only on for a few minutes to prove a point, a bipolar is on order now!
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Old 3rd Aug 2019, 8:52 pm   #6
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Default Re: Metamec Kundo Quartz clock capacitor

Bipolar bought, fitted and normal operation resumed, thanks all, mods please close.
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