Quartz anniversary clock pendulum mechanism

Discussion in 'Clock Repair' started by johnrams, Mar 13, 2017.

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  1. johnrams

    johnrams Registered User

    Mar 13, 2017
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    I have acquired a German made clock - actual manufacturer unknown. It operates from 1 type AA battery. The time part works fine, but the dummy pendulum mechanism does not, and I wondered if anyone had ideas for repair? I realise the pendulum has no connection to the actual timekeeping and is purely decorative.
    The pendulum runs in a bearing at the bottom on the base plate in a cup which contains oil. It seems to move fairly freely. The motion is generated by two magnets which pass either side of a wound coil in the back of the top part of the case. But there does not seem to be any power being applied, so spinning the pendulum will achieve a couple of revolutions but then momentum is lost - it slows and stops.
    There appear to be 3 fine wires coming out of the coil which are soldered to pins at the sides. I am unsure how the pulse of energy is generated - there clearly should be some sort of switching which activates the coil each time the magnets pass, but there is no mechanical switch as such. DSC_0413.JPG
    Does anyone have any ideas? It is not worth spending much money on this, but if any easy solution is available that would be great.
     
  2. roughbarked

    roughbarked Registered User

    Dec 2, 2016
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    Such mechanisms are virtually unbreakable. The coil may be damaged by people poking things in it but otherwise leaky batteries may corrrode the contacts and wires. From memory, these also had a hairspring to keep up the momentum. Can you get the back off the clock without breaking the plastic?

    One thing that always improved things was to put some sticky tape on the magnets and peel it off along with all the magnetized metal particles.
     
  3. John Hubby

    John Hubby Principal Administrator
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    Johnrams, welcome to the NAWCC Message Board! Thanks for your inquiry and the photo of the problem clock.

    First of all there should not be any oil in the cup that supports the pendulum. The usual construction has a concave sapphire bearing at the bottom of the cup, with a hardened steel pin in the bottom end of the pendulum shaft that sits in the bearing. These are designed to run dry and the presence of oil, especially if it gets contaminated with dust, can cause enough drag to keep the pendulum from turning.

    This particular design usually relies on a physical contact to energize the coil that impulses the magnet mounted on the pendulum, however some models are electrically triggered using a small secondary coil. The return force is provided by the coil spring that looks like an alarm clock hairspring seen underneath the lower magnet support. You may need to remove the back cover to see exactly what is there, that should be done very cautiously as it is easy to damage the coil return spring on the pendulum.
     
  4. johnrams

    johnrams Registered User

    Mar 13, 2017
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    Yes there is a hairspring, which seems OK. Also the wires seem free of corrosion. I have tried the sticky tape trick on the magnets, but it makes no difference. As in my photo, this is the access from the back - any further access would have to come from the front my removing the hands and face, but I'm not sure this will achieve anything.
     
  5. roughbarked

    roughbarked Registered User

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    Does the coating on the coil wires appear damaged? Otherwise as with all such devices, they need to be running at accurate distances from the coil to magnets. ie: clock needs to be level horizontally and vertically. Some, not all, had ajustment to set these tolerances. Mostly the plastic ones didn't but it is worth a look for adjusting screws. The bottom pivot, underneath the base of the clock. can this be adjusted?
     
  6. johnrams

    johnrams Registered User

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    On closer examination, there are actually 4 wires coming from the coil - 2 of them connect to the same terminal pin. I assume therefore that as there is no mechanical switch, this is done electronically. The secondary coil must be wound in the same casing as the main magnetic coil. I am trying to remove the oil from the bearing as suggested....
     
  7. johnrams

    johnrams Registered User

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    Hmm - there is, or was, an adjustment screw under the base that would raise the bottom pivot. Unfortunately it looks like someone has already tried this, but in so doing has damaged the brass screw so that the slot is no longer there and the screw cannot be turned.
     
  8. roughbarked

    roughbarked Registered User

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    Do you have a slot file? If so a new slot may be created.
     
  9. johnrams

    johnrams Registered User

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    Afraid I don't have such a file, but in any case this would not be successful as the screw is recessed into the surround. The only other idea I have would be to file the supporting pillars at each side to make the pendulum ride higher...
     
  10. roughbarked

    roughbarked Registered User

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    I'm not sure what you mean by that but it sounds like a last resort that could indeed be the last.
    Maybe the adjusting screw is a dummy that somebody wrecked thinking it could be moved? Otherwise it may be turned with thin nosed pliers?
     
  11. Tinker Dwight

    Tinker Dwight Registered User

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    It is likely that the circuit uses a single transistor ( PNP germanium ).
    It may also use a 4 terminal IC. In some rare cases, it could use a
    part of the clock's main IC.
    Some pictures of what is there would help to determine the next direction to go.
    Tinker Dwight
     
  12. johnrams

    johnrams Registered User

    Mar 13, 2017
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    At the moment I am pursuing the idea suggested earlier that the problem may be wear in the bearing at the bottom of the pendulum shaft, which is causing the magnets to pass insufficiently close to the coil. There is an adjusting screw under the base, but this is damaged and as the slot in the screw is below the level of the hole into which it fits, I do not think it possible to re-cut the slot. I'm afraid the photo is not very clear..
    clock under.JPG

    I am unsure how critical is the distance between coil and magnet. The only way I have to alter this is to shorten the pillars which support the upper part of the clock. This may be worth a try before looking into the electronics.
     
  13. roughbarked

    roughbarked Registered User

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    #13 roughbarked, Mar 14, 2017
    Last edited: Mar 14, 2017
    I wouldn't alter anything without attempting to learn about why it was made that way in the first place. I've had a think about what I've said and it is far more likely that What John Hubby said was correct. I must have missed his post earlier.


    Now initially, you said it had oil in this cup.
    I'm going to suggest that you use detergent and water to clean the oil out. Dry it well. Do all this without breaking anything and the clock will likely actually work.

    You can use a thin toothbrush if you hold the pendulum in one hand so that it doesn't get any wild swings up and damage delicate things like hairsprings.
     
  14. Tinker Dwight

    Tinker Dwight Registered User

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    I've not see this exact clock but I'm familiar with the general
    mechanism. Looking at the picture, I see two magnets, top and
    bottom. This would indicate to me that the only purpose of the
    height adjustment is to ensure that the magnets don't drag
    on the coils. Otherwise the height is not critical.
    All it takes is to break one tiny wire and things don't work anymore.
    I can see in the picture, there are two colors of wire for the coil.
    This is typically how Haller did their coils. I forget which is which
    but I believe the larger coil is the sense and the smaller is the
    drive coil.
    One can often measure the coil with an ohm meter but sometimes
    it is hard to separate the other parts from the coil. One needs to be
    careful to not disturb the tiny wires and only measure at the PC board.
    I've found a simpler test is to put the meter on a low voltage scale and
    wave a super magnet by the coil. A mechanical meter works better for
    this than a digital.
    The super magnet will induce a current in the coil seen on the meter.
    Of course, this is a done with the battery removed.
    I would test the condition of the coils before fiddling with other adjustments.
    Tinker Dwight
     
  15. roughbarked

    roughbarked Registered User

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    The coils can be tested without worrying about cleaning the bottom bearing if indeed there is one. I agree. Usually one can visually see damage to coils but this isn't always the case.
     
  16. Tinker Dwight

    Tinker Dwight Registered User

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    I should also note that one should not let a super magnet get anywhere
    near the armatures magnets. They will slam together, most likely shattering
    the ceramic magnets on the armature.
    They will make a mess of a hair spring as well.
    Super magnets are dangerous to soft human tissue. If your finger
    happens to get between the magnet and a metal piece it wants
    to stick to, it will pinch skin enough to draw blood.
    Tinker Dwight
     
  17. johnrams

    johnrams Registered User

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    The latest development is that I have tried filing down the side pillars to effectively raise the position of the pendulum, but this has not made any difference. It is correct that there are 2 colours of wire to the coils so I will test the resistance with an avo-meter. Access to the other electronic components would involve splitting the top case and removing the rear section, but this would also mean releasing the hair spring on the pendulum, which I am reluctant to do.
     
  18. roughbarked

    roughbarked Registered User

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    #18 roughbarked, Mar 16, 2017
    Last edited: Mar 16, 2017
    Now you know what I meant about not changing anything without knowing what it is there for.
    As for the hairspring, it is only a pin to remove and gently turn the balance until the hairspring is free. Don't lose the pin.

    I strongly recommend that you read back at John Hubby's post. Consider what he mentioned about drag. Look where he mentions a steel pin and a sapphire bearing. See what possibly may be causing drag here. Hairs? Dirt? http://mb.nawcc.org/showthread.php?141267-Quartz-anniversary-clock-pendulum-mechanism&p=1097945&viewfull=1#post1097945
     
  19. johnrams

    johnrams Registered User

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    I confess to not having done anything since the last post, as we have had the birth of a new grandchild! Now this has settled down, I may be able to continue. My question is that if I open up the mechanism and expose the electronics, other than testing the integrity of the coils, what else can I do? I only have limited test equipment - an Avo meter.
     
  20. Tinker Dwight

    Tinker Dwight Registered User

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    We can see if it is a transistor or an IC that runs it. If it is
    a transistor, those can be replaced. The IC is only available from
    damaged clocks.
    If the coil is shot they can be rewound.
    Tinker Dwight
     
  21. AJSBSA

    AJSBSA Registered User
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    I am in the process of converting a quartz 400 day timepiece to mechanical because the electronics are beyond fixing apart from the hands it will look identical from the front and better from the sides. I offered this route to the customer and he and his wife decided this was what they wanted as it had sentimental value I will post the results if there is interest it will say Quartz on the face which will be a bit odd.
     
  22. johnrams

    johnrams Registered User

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    I have finally dismantled the mechanism, removed hair spring and pendulum and accessed the circuitry. The coils are both OK - there is continuity tested with my meter. From my limited electronic knowledge, there appears to be a couple of capacitors, resistors, one transistor and a small IC chip on the board. Not sure where I can go from here though..... DSC_0422[1].jpg
     
  23. Tinker Dwight

    Tinker Dwight Registered User

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    The IC usually just runs the clock movement. The transistor
    runs the pendulum.
    They are usually to separate parts.
    If the coil for the pendulum is still good, there is only
    a small amount of circuitry involved in the pendulum.
    The two likelies are the transistor or the large black
    electrolytic capacitor.
    If you can show the circuit side of the PC board, I can
    check the circuit layout to see if I'm right about the
    pendulum and IC being separate.
    Also if you could indicate the power supply polarity,
    that will help me as well.
    Tinker Dwight
     
  24. Tinker Dwight

    Tinker Dwight Registered User

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    My mother in law just brought me a Elgin ( made in the USA ),
    she found at a garage sale.
    It has the motor in the base to spins the pendulum.
    It used the top plastic for a bushing. I checked the plastic
    with brakeklean and it disolved it so I just added oil.
    The circuit looks similar to yours.
    The old oil was really sticky. It still felt like is spun freely
    but the old oil was the problem.
    Fresh oil and spinning it brought it back to life.
    These motors don't have much torque. They are intended
    for long battery life.
    The point is, make sure the bushings are really clean.
    even if it feels quite free, the motors in these use so
    little power that it doesn't take much to stall them.
    Tinker Dwight
     

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