Need help with pendulum clock

Discussion in 'Electronics Repair' started by Redeye02, Dec 15, 2011.

  1. Redeye02

    Redeye02

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    Hi.I'm having a problem with my pendulum clock. the pendulum won't swing anymore I have this mantle clock which has a battery operated circuit which makes it's pendulum swing as a bobbin coil passes a permanent magnet. the power supply is 2 AA batteries. they are connected to a small circuit board. the components on the board look like 2 transistors, a 10v 47uf capacitor, some diodes or resistors, and a bobbin like coil. what would be the most likely component on the board that has failed? is there a schematic available similar to this design anywhere so that I might get all new parts for the board? thanks for any help
     
    Redeye02, Dec 15, 2011
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  2. Redeye02

    duke37 VIP Member

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    Wecome Redeye, I feel like that this morning

    The most likely fault with the clock is bad battery connections - measure the voltage on the printed circuit board.
    The coil may have corroded and be open circuit, check with a meter.
    The capacitor may be faulty - easier to check by subsitution.
    The transistors, if removed, can be checked with an analog meter. One may be npn and the other pnp.
    Resistors and diodes are not likely to fail.
     
    duke37, Dec 15, 2011
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  3. Redeye02

    Redeye02

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    thanks for the info. I reterminated the battery wires but no help. I will remove the transistors and check them with my meter.If I can identify them I will try and replace them and also replace the capacitor. finding a replacement board is almost impossible. I contacted the vendor and was surprised that they ill send me an entire replacement unit but I still believe I can get this one working again.
     
    Redeye02, Dec 15, 2011
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  4. Redeye02

    duke37 VIP Member

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    I Googled free pendulum clock and got an article by Ron Elliot which has a couple of diagrams.

    sound.westhost.com/clocks/free-pendulum.html

    His clock failed because of corrosion of the very fine coil wire. Have you tested the coil for continuity?

    Duke
     
    duke37, Dec 15, 2011
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  5. Redeye02

    Redeye02

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    thanks for the help. I checked the coil and it's ok. my next step is to get a pnp and a npn transistor to try and replace them one at a time and hope one of them has gone bad. the circuit is so simple with just a few components. I seriously doubt that the cap is bad and no components show any heat damage. if I can locate a 47uf cap I will get one too. these components are very inexpensive so I will not be at much of a loss. I came across a few schematics now and my best guess would be a faulty transistor causing a no charge state in the capacitor as the coil swings past the magnet. you'd think that some vendor out there would carry this sort of pendulim drive but I couldn't locate anyone. I'll get it working if I have to build another one from scratch.
     
    Redeye02, Dec 16, 2011
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  6. Redeye02

    davelectronic VIP Member

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    Hi there. Ive been following your thread with interest, i am often the same, determined to fix it, why go out and buy another when a fix is possible, i would say you've ruled out the worst senario, the coil break down, how ever if your going to test the transistors, then i would replace the capacitor as well, especially if its an electrolytic. Anyway good luck with the fix.
     
    davelectronic, Dec 16, 2011
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  7. Redeye02

    Redeye02

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    I located a schematic similar to what I have. a magnetic pendulum. one thing that puzzles me is that my board doesn't appear to have a diode.the circuit I'm looking at has 2 transistors, one diode,3 resistors, and a capacitor.my board has 2 transistors, 4 resistors, 1 47uf cap, and a tiny nf cap. all this stuff can be bought at the local electronics hobby store. the vendor is supposed to send me a brand new unit but I am determined to fix this one.I don't have a strong background in electronics but I can solder and this is a fairly simple task. I will post back if I can get this pendulum swinging again. Once the magnet has passed the ciol and the capacitor is charged the transistors will switch on and off so I suspect a faulty transistor. anyway they are simple to change.
     
    Redeye02, Dec 16, 2011
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  8. Redeye02

    electro_pa

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    Need magnet checked.

    Hi Redeye02,
    Don't forget, check the magnet! Has it lost strength?
    The circuit won't energise without sufficient trigger amplitude.
    What material is magnet made from?
    Metallic magnets have possibility of becoming weak, from age, mechanical shock, being subjected to external magnetic fields.
    Cheap mechanism could have poor quality magnet material.
    Has it been hitting the coil assembly during use?
    Ferrite/ceramic-based magnets usually do not suffer loss of power.
    Regards,
    Clive.
     
    electro_pa, Dec 19, 2011
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  9. Redeye02

    Redeye02

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    Redeye02, Dec 19, 2011
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  10. Redeye02

    Redeye02

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    Redeye02, Dec 19, 2011
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  11. Redeye02

    snakeriver

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    pendulum clock circuit

    I have the same problem as described by Redeye02. My Westminster chime and clock work however the pendulum does not. The clock and chimes operate by "AA" batteries. The pendulum has a separate "AA" battery connected to a small circuit board. There is a magnet mounted on the pendulum. The circuit board has a coil and two other components which I don't know their function (one maybe a transistor). I have had no luck in finding a replacement board. Does anyone have a fix, or know where I can find one.
     
    snakeriver, Jan 21, 2014
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