Troubleshooting Junghans ATO

Discussion in 'Electric Horology' started by Chris, Jun 14, 2008.

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  1. Chris

    Chris Registered User
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    OK, a Junghans ATO came in today with a dead battery. I noticed that in Merritt's catalog, there is a conversion box to accept 2 AA batteries instead of the old box battery. So, since it is on backorder, I tried an experiment. I tape two AA's together, ran a metal contact to connect both positives and negatives together and then ran the two wires to the batteries. Nothing. I reversed the wires and still nothing.

    Am I being to literal by tying the batteries together as I have? Do I assume the red wire is the positive and the yellow negative? How can I test it for magnetic operation? Thanks, Chris.
     
  2. Glyn Meredith

    Glyn Meredith Registered User

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    What is the voltage it should run on with the "old box battery" Chris? What voltage is written on the dead battery?

    If you gang positives and negatives you will be supplying around 1.6v - the cells will be in parallel. If there is a conversion on the market, that's probably how it's configured. If it needs 3 volts+, you just turn one battery around and put them in series.

    There are many work-arounds with batteries. A few bits of wire, some tape and a bit of knowledge will allow you to run various configurations to suit your need.

    Added: ATO clocks need to run with the polarity correct. If you reverse that, it won't work. I think you have to get the pendulum started by hand - it won't get going by itself. You will need to test for continuity in the circuit, if the correct power supply does not work.

    Glyn
    Click Here for Global Horology - building a global horological community
     
  3. eskmill

    eskmill Registered User
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    Post WWII Junghans ATO battery clocks are designed to operate using a 1-1/2 volt dry cell. The size of the dry cell is immaterial only affecting the useful life of the cell. They will operate for months on a single AAA cell and years from a "D" size alkaline flashlight cell.

    It is important to understand that both the Bulle and ATO battery clock circuits are, in electrical terms, "weak current." They operate on micro-amperes; observable battery current is miniscule using conventional volt-ohm-milliammeters.

    If the polarity is incorrect, the pendulum motion will be dampened and stop.

    If the pendulum won't oscillate but the movement appears to be free, then closely observe the tiny, thin delicate contacts that should have minimal motion when operating. Observe the contacts in good light and possibly with a magnifying glass.

    The contacts are delicately thin gold and must not be abraded else the gold will be destroyed. Instead, slip a thin slip of clean paper between the contacts while operating the movement manually to wipe any dust that might interfere with the electrical contact.

    The contacts are located in the circled area in the photo below.
     

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  4. Chris

    Chris Registered User
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    The old dry cell was 1.5 volts. Going by the picture in Merritt's catalog, it appears that the positives are grouped together and the same for the negatives. So, if correct, which wire is which? Is the red positive or is the yellow? Thanks.
     
  5. eskmill

    eskmill Registered User
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    Chris. On three examples I just examined, the red wire leading to the contact assembly should connect to the + (positive) terminal of the dry cell and the yellow wire eminating from the drive solenoid coil should connect to the minus (-) terminal of the dry cell.

    As I stated in my earlier reply, if the dry cell connections are reversed, it will be readily apparent. The motion of the pendulum will dampen and slow rapidly compared to having no battery connection whatsoever.

    Many battery clocks have suffered from dry cell chemical corrosion. The wires may have been replaced with whatever color insulation is at hand, thus the simple observation of backward connection and dampened oscillation is more reliable than the colors of the connecting wires.
     
  6. DC Kelley

    DC Kelley Registered User

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    As Eckmill observed, red is positive. Using one cell is sufficient (two in fact may give a longer interval between changes but nothing else). You don't expressly say if your ATO is of the mechanical switch type, or of the later transistorized models (in which case the switch assembly shown in Eckmil's pic is gone). If it is the mechanical style, you can simply check the coil for continuity, then confirm that the switch contrats are working. The transistor one is a bit harder to troubleshoot.
     
  7. Chris

    Chris Registered User
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    DC:

    It's the early style with the gold contacts. How do I set the contacts? Should they be able to be moved backward by the metal pin that touches them or should they stay in constant contact? I don't think they are set properly at the moment (looks like they were played with at some time.)

    It was running for several minutes today, but I looked at it cross-eyed and it went dead! How do I test the coil? Thanks, Chris.
     
  8. eskmill

    eskmill Registered User
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    The metal pin that makes contact with the pair of gold covered contacts should cause the gold contacts to move slightly but only when the clock is in motion. The moving contact pin must not be in constant contact with the thin gold covered contacts. There are two contacts in parallel as a safety factor. The contacts motion should be as slight as possible yet reliable.

    The contact closure is brief and the view with the clock face installed is difficult. I use a magnifying glass and a flashlight to observe the motion of the contacts on the Junghans ATO clocks. The adjustment is a screw below the contact assembly. The adjustment "bends" the contact bracket toward the operating pin giving more motion to the gold contacts.

    The design of the Junghans ATO battery clock is such that the pendulum is given impulse just as the pendulum arrives at its mid-point of motion. An early impulse is not desired and a late impulse after the pendulum has passed center will have little effect. The clock should be on a level surface.
    Its designers, created a very efficient and reliable timepiece with minimal adjustments.

    You may test the continuity of the solenoid coil with an ohmmeter. The resistance off hand should be in the range of greater than 2000 ohms and not more than about 5000 ohms. Rarely is there a problem with the coil although the leads where they exit the frame is subject to tear the insulation. One lead of the coil connects to the clock metal frame, the other (yellow) lead connects to the dry cell.
     
  9. DC Kelley

    DC Kelley Registered User

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    Eckmill's description is precise and correct and I defer to his greater experience, but I would emphasis that the moment of contact is very "brief" to the point of being and short as possible (on the transistorized model on the order of a few microseconds) so, please dont adjust it too far. Too far will simply waste battery power and will increase contact wear, too little it will not run, perhaps the rule should be expressed as "as little as possible" here. [Aside: I have never instigated it, but I suspect that there must be a small amount of contact bound on this switch that may cause the arcing and eventual wearing down of the pads]

    And by the way you can get the converter box from Timersavers too. The terminal on these things are not a precise fit (for the Kundo models) but for the ATO you will likely be connecting simple bare wires. Good luck.
     
  10. praezis

    praezis Registered User

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    All facts were already correctly described, I want to add a few details:

    The distance between gold contacts and platinum pin must be 1/4mm.

    The contact must open when the pendulum reaches (from right) the left mark (line) on the scale below.
    Returning from left to right, the small switching arm on the pendulum must fall from the tooth of the contact wheel, when the pendulum reaches the right mark on the scale.
    Both are audible when you guide the pendulum with slow motion.
    These positions are adjustable with two screws on the pendulum, but I do not recommend to fiddle around there.

    In fact the range with contact closed must be symmetrical to both sides of the middle position. This is essential for isochrone performance (independance of driving force and amplitude)!

    My tests gave a coil resistance of 1700 ohms for newer and 2500 ohms for older types. All descriptions refer to the 1/2s wallclock ATO.

    In the last years I made many tests with ATOs during development of a radio-control system for this type of clocks. The device contains the dry cells and is simply changed against the original cell.

    Regards,
    Frank




     
  11. Chris

    Chris Registered User
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    Ok, this may sound stupid, but how do you test the coil? Where do I hook up the test leads?

    On this one, I looked at the wire coming out of the coil and going to the battery and noticed there were only a few strands holding it together. I cleaned up the strands as best as possible and soldered fresh wire to it.

    I had it going for about five minutes and then it would stop. It seemed to have good motion, but then crapped out.

    I have another one as well, which has a battery recepticle behind the vertical movement frame which holds two D batteries. I'd like to get it up and running too, but one at a time I guess.
     
  12. DC Kelley

    DC Kelley Registered User

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    Testing a coil is easy, but you need a multi-meter (any type will due). You connect the two coil wires to the meter (polarity, that is which wire goes where, does not matter in this case) and see that it is continuos across the coil (in English, that the coil of wire is in fact intact with no breaks). You can do this with a simple light type continuity tester as well, but a multi meter is better, because you can also read the resistance of the coil, which in this case should be around 2000 ohms (I would guess a range of 1500 to 2500 would be typical).

    The ATO uses the frame of the clock to form one of the two wires leading back (through the contact switch) to the battery, much like the frame of your car is used as the negative side of things. It is important that this wire/frame/wire path be intact, or you will not have a loop back to the battery This can be tested the same way, place the meter on the wire which connects to the frame, and the other lead on the battery terminal, you should see continuity with only a ohm or two of resistance.

    Offhand, I don't know of anyone making a replacement holder for the style where the battery is in the back, the ones I have a seen and own all use the same alum box to hold a couple of cells underneath, converted to that format. Not quite authentic, but prettier in my mind then seeing the battery behind it.
     
  13. Chris

    Chris Registered User
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    Ok, here's what's going on: The negative wire is ok, but the coil is not.

    When I test the coil, it's extremely intermittent. I can get a measurement of anywhere from 1300 to 1900 ohms, but it's only for a split second and I have to jiggle around a bit. I unwrapped the coil and resoldered the outer end. The inner end, however, cannot be reached. Does it sound like a break to you? The inner end is the one that leads to the positive terminal on the battery and was barely holding on by a few strands. I soldered the break with electrical solder and "fluffed up" the broken strands and exposed new wire first.

    Anyone re-wrapping these?
     
  14. DC Kelley

    DC Kelley Registered User

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    This certainly sounds like an intermittent connection from all you have said. The darn things always seem to break on the which ever side is harder to get to and unwrap. If you can not get enough of the of the existing wire out to make a good connection, you probably should re-wrap it. My mechanical ATOs are at work, and I am at home at present, when I get there I will look over the coil and see how hard a re-wrap would be. I am reluctant to recommend this to someone when I can not ensure it working, but that looks like your next step.
     
  15. Chris

    Chris Registered User
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    Keep me posted. It looks like there are a lot of windings involved. Also, is there a transistor or circuit buried under the windings as well?
     
  16. eskmill

    eskmill Registered User
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    The Junghans ATO battery clocks, to my knowledge aren't "transistorized;" all made by Junghans have the battery/solenoid circuit operated by dry electrical contacts.

    The Junghans ATO solenoid has only one coil and should not be confused with the solenoid used with the KundO transistor switched battery pendulum clocks.

    Your resistance measurement of 1500 to 2000 ohms was in the normal range. The coil is wound of thousands of turns of very fine wire and easily broken. As luck would have it.....usually the break is at the start end of the coil underneath hundreds of layers of fine wire!

    Rewinding the coil would be difficult.....it would seem more practical to replace the soleniod coil assembly with one salvaged from an appearance damaged Junghans ATO battery clock.

    Not related to your Junghans ATO clock problem, I believe it is important to note that the ATO company (Etablissements S.A. Leon Hatot) at the LePaute division, produced a very few transistor switched pendulum clocks circa 1953-54 that mechanically resemble the Junghans ATO battery clock.
     
  17. Chris

    Chris Registered User
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    Ok, so now the question is...does anyone have some spare coils:???:
     
  18. eskmill

    eskmill Registered User
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    Frank's (praezis) adjustments read like they were written for the Junghans ATO maintenance book.

    As an aside, I disassembled a non-working one that I had purchased for parts this week end. Its appearance was bad from dry cell chemical corrosion. But worse was the burned gold contact assembly. The photo is below.

    I believe the burn was probably caused by using the wrong battery or that the dry cell negative connection was inadvertently connected to the clock case metal, leaving the 2000 ohm solenoid coil out of the circuit. That would impose the full 2200 milliampere dry cell current to the delicate contacts.

    For what it's worth, I burnished the moving contact pin and reversed the gold contact assembly so that the back or reverse side of the gold contact is used. The clock is back together and works with vigor.
     

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  19. Ralph B

    Ralph B Registered User

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    Chris,

    My own clock has a re-wound coil that I did myself, and I have done a couple of similar ones including the coil in the timing clock at the local sports stadium.

    It is not difficult, just extremely tedious if you don't have all the professional re-winding gear, (which I don't).

    You do need a lathe that you can adjust the speed to run at 100 to 200 rpm. A drill would be way too fast.

    Also a reel of some sort that you can fit into the lathe to wind all the wire onto. I used a plastic reel that once had nylon fishing line on.

    Find the free end of the wire on the coil, and tape it to the reel.
    Stick a pencil or dowel through the coil and fire up your lathe.
    As long as your arm is about half a meter away from the lathe and is quite relaxed it acts as a sort of shock absorber for the occasional little snatch that occurs.
    The wire is really fine, and you would think extremely fragile, but it's surprising how well this unlikely sounding procedure works.
    I suspect that the wire has a little bit of give in it as it's copper.

    Any breaks will be obvious because the un-winding stops and then it's time to scrape the shellac off the wire and do some delicate soldering.

    To re-assemble, reverse the process, ( as they say in all the repair manuals!). i.e. put the coil in the lathe and hold the reel in your hand.

    As I wound it back on I would periodically stop and check with a meter that there was still continuity between the end of the wire, ( feed out from the center of the coil), and the wire that was about to go onto the coil.

    The wire going onto the coil is , of course, covered in shellac/varnish so a tiny bit needs to be scraped off to enable a meter probe to make contact.

    It all sounds a bit long winded but once mastered you'll be able to repair any coil that you can't get a spare for, so good luck!

    Ralph B
     
  20. DC Kelley

    DC Kelley Registered User

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    I had a chance to disassemble an ATO coil today, the winding is very straight forward, just a simple back and forth pattern. You could rewind this thing if you wanted to, just chuck it up on your lathe and take it fairly slow. Ralph B suggested unwinding the coil then re-using that same wire. I would advise against that because the 50+ year old shellac may not take multiple bends well and this may in turn short out the coil if it flakes off.

    If you take the final wrapper off that is show in Eckmill's picture, you will see the yellow wire is given a few final wraps (a stress reliving technique) and if you are really lucky may get a bit more wire to try and connect to the positive side. Duplicate this when you rebuild it. I am guessing that this is a 32 to 40 gauge wire, it is at least 32 (I never have learned a definitive/precise way to measure the gauge of very small wire under 30 AWG other then with a micrometer and turning, would love to learn).

    There is an ebay seller called "swordandtreasure" that seems to carry this sort of thing (no relation to me). See items 150262861278 or 120277653127 from another seller for examples. About 800 feet should serve, note that this stuff is now covered with enamel (shellac is no longer used) and that it is rated for what temp it can work at. Any of the temps you see would be fine for this type of use (unlike a motor it is essentially room temp all the time).
     
  21. Ralph B

    Ralph B Registered User

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    Chris

    New wire would be the way to go but I was not able to find any so I had no choice.
    Mind you I've had no problems since and the shellac seemed quite stable with no flaking.
    Miking the wire gave me 0.0032 with the shellac and 0.0027 inches without. What wire guage this is I don't know.

    I have since found the notes I took at the time to remind myself of the amount of wire required. This was partly curiosity as in the real world you'd just wind it on until it was full.

    I weighed the coil before and after which gave me a net copper weight.
    Then weighed 250mm. of wire on some lab scales which will weigh to 1 ten thousandth of a gram, ( they'll weigh a single hair !).

    Doing the maths gave me 2,430 feet or 810 yards.

    I've not had reason since to see if I'm right but it's probably a good place to start if you're buying wire.

    Cheers
    Ralph.
     
  22. DC Kelley

    DC Kelley Registered User

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    The measurement Ralph made suggests finer than 40 AWG, but this wire (coming from pre metrication Europe) may use another size scale. Metric sizing is like collet sizing, in increments of tenths of a MM, see the link below.

    Given that the coil clearly states 2k resistance, and using the table below, this suggests a 40 AWG wire length of about 2000 feet is needed, my advice in my last post was wrong (was 800 feet), you will need more wire. BY the way this wire on a commercial sized spool is typical sold by weight not length, but these ebay seller show it in weight.

    Here is a useful table to check with, but it only goes to 40 awg
    http://online.physics.uiuc.edu/courses/phys436/spring06/Lecture_Notes/P436_Supp_HO_01/American_Wire_Gauge.pdf
     
  23. tppa

    tppa Registered User
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    Hi, I fallowed you directions on rewinding an ATO coil and it went quite well. I did as you stated on my lathe. I do need to know however which end goes to the positive term. on the battery and which end to ground or does it not matter. The coil I was working with had both old ends of the wire broken off. Any help would be appreciated.
     
  24. eskmill

    eskmill Registered User
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    Congratulations on rebuilding the ATO solenoid coil Tppa. And, welcome to the NAWCC Message Board.

    You ask, "I do need to know however which end goes to the positive term. on the battery and which end to ground or does it not matter."

    Yes, it connections to the 1.5 volt dry cell does matter, else the magnetic field in the solenoid will push the N-S permanent magnet backward instead of pushing it through the solenoid when the contacts make.

    That said, the connections to the start and finish ends of the solenoid coil depend on which direction the wire was wound! There are left hand and right hand rules governing the direction of a magnetic field in a solenoid that are beyond explanation here. (I always get them wrong)

    Just let me say that if the polarity of the connections is correct, the ATO battery clock's pendulum will oscillate freely. The opposite is true as well; if wrong, the pendulum, set in motion with a gentle push will noticeably retard and finally stop.

    A static check with a single dry cell connected briefly with the pendulum magnet motionless at the midpoint will demonstrate right and incorrect battery connection.

    Good work! :Party:
     
  25. tppa

    tppa Registered User
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    Thanks Allot, I am going to give it a try and I will let you know how it turns out.
     
  26. tppa

    tppa Registered User
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    Hi, I had success, I put the coil on the clock but not completely assembled and it's running like a champ. The only problem I am having now is that it is 15 min. fast in 8 hours give or take. I have the rating nut all the way slow, did I put too many windings on the coil or not enough ? Oh, it was the outside end of the coil winding to the neg. term.
     
  27. Kevin W.

    Kevin W. Registered User
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    tppa how would you rate this job, difficult or not bad, i am tempted to try to fix my own Ato but not sure about it.
     
  28. tppa

    tppa Registered User
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    Hi, I just wanted to let you know I figured out that I had wound to much wire on the spool which created to much of a field. I have taken some of the windings off and now I think I am close to the right amount of windings which has now slowed to the point where I think I can start to regulate the clock. Thank you for your help.
    -> posts merged by system <-
    Well, it was not too bad for my first time trying to repair a coil for one of these clocks. I had allot of help by asking questions on the site which saved me wasting time. It took patience to wind the coil, I used my lathe as suggested and it worked just fine for winding the coil and it made a nice looking job.
     
  29. Francygh

    Francygh Registered User

    Dec 11, 2008
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    Dear Praezis,
    Please allow to introduce myself: I am Francesco. I own an ATO Junghans clock. The clock is not working since many years ( more than 20). I live in Milan Italy. I took the clock to many shops to fix it but all of them failed. I sincerely think here in the shops nobody knows how it works. They tried to put 3 V battery with a 400 Ohm impedance and Zener diode etc. but everything failed. I discovered this forum, so I decided to not give up.
    I gave a look by myself to the ATO. The coil is a 1450 OHM 1.5 volt and I measured with the voltmeter it is in a perfect shape.
    I pushed the pendulum to allow few oscillations and I saw that most probably the trouble is in the contacts. The pools and the pin movements moves apparently well but the gold contacts looks to me wear out. To my understanding the 2 contacts are copper with a thin gold deposited on them. By eyes I recognize more the copper or brass color rather than yellow gold. It is likely somebody tried to clean the contacts with file or glass paper if they saw a small spark or arcing, as somebody said in the forum. I wonder where it could comes since we are talking of a microAmperes current. Another point is that I am no longer sure of the mechanical alignment of the brackets and gold contacts with respect to the platinum pin. I watched many videos on Yahoo. To my understanding the bracket should keep the contacts at the right distance from the pin, so If I turn the adjusting screw clockwise I should see the bracket going toward the pin and the contacts follow it. In my case I see only the bracket moving. If this is correct the hole in the contacts became larger and the screw has no longer play on them ?
    How do you measure the 1/4 mm with the pin in rest position?
    The platinum pin is made all platinum or it has also a deposit that can wear out?
    I understand I am asking you many questions . I wonder if you could be so kind to tell me what check can I do. From office I can also send you a couple of pictures I have in my PC there.

    Looking forward for your reply I thank you in advance for your courtesy
    Best regards,
    Francesco



     
  30. eskmill

    eskmill Registered User
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    I have a functional Junghans-ATO battery-pendulum clock in view just above my computer display. The ratchet driven seconds hand has been ticking away the seconds for several years without fail and more-or-less within minutes of UTC depending on room temperature.

    I've bought and traded several versions of the Junghans-ATO clocks over the past ten years, repaired a few and discarded a few because they had either been ruined by repair attempts or were left to the elements with their glass enclosure broken or missing.

    Mechanically, they're simple but must be clean and operate free of friction. They must be reasonably leveled on a substantial platform free of vibration so as to assure the driving pawl reliably dirves the ratchet wheel. Some suggest that the pivots should be free of lubricants but I believe a quality watch oil can do no harm so long as the electrical contacts are dry.

    The timing of the electrical contact closure relative to the position of the magnetized pendulum rod's travel in and out of the driving solenoid is set by the design and not adjustable. The contact closure is brief but must be positive to provide a small measure of repeat-ability and just enough to provide a minimal amount of "wipe" so as to assure a clean contact area. I personally observe the contact closure using an eyesight magnifier. I look for both gold contacts to have a very slight bending motion when the precious metal moving contact rod makes the touch to the gold tips.

    On several I've encountered, the gold tips appear to be badly pitted suggesting erosion from contact arcing which seems unreasonable owing to the tiny solenoid current. Erosion of the gold contact might be exercibated by accumulation of abrasive dust. I have been able to re-adjust the position of the gold-tipped fingers to a new unused area of the gold contact by carefully relocating the contact mounting bracket very slightly.

    On one example, I discovered that the solenoid coil had been replaced and apparently the wires had been transposed or the coil bobbin inserted backward. I finally observed that the pendulum motion was being retarded instead of being accelerated. I thought reversing the dry cell in the holder would resolve the problem but finally replaced the solenoid with one salvaged from a donor movement.

    Note in the snapshot below that the contact pair on the left are pitted and the set at right although the brass corroded, the tips are fresh.
     

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  31. praezis

    praezis Registered User

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    Hello Francesco,

    the gold contacts and probably also the platinum pin have a thin tube of precious metal over the base metal. If they are really worn it is possible to loosen this tiny tube and fix it again in a new position.

    You are right, if you adjust the bracket, the contact springs should follow. They rest with some tension (0.5 grams) on that bracket. Else you must bend the springs with caution.

    As a first test I would connect an ohmmeter to the clock's battery leads. Guide the pendulum slowly from right to left. In the middle sector the meter must show the coil resistance. Else search for broken connections or contacts always open.

    The contact gap you may estimate with your eyes if you have no better tools.

    Regards, Frank
     
  32. Francygh

    Francygh Registered User

    Dec 11, 2008
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    ATOFG1.jpg ATO2FG.jpg

    Thanks everybody for the quick answer!

    Attached are two pictures of my ATO. Everything is original . Coil is original in perfect shape polarity ok. Only the glass cover was destroyed . But at the moment is not a problem. One of the pictures shows a particular of the contacts. Leverages move very freely since they have been cleaned with a special cleaner solution used in horologery. I saw several movies on yahoo on ATO restored. As you said the bracket keep the contacts in place in order that the electrical contact occurs with the right timing.
    As you see in my pictures I am not able to keep the contacts close to the bracket and most of all I do no longer know the right position of the bracket with respect to the platinum pin.
    Please have a look to the tips of the contacts. It looks to me of copper or brass and the thin gold is totally wear out. I am sure because technician on shops told me they kept clean the contacts with files since they saw arcing. I can find somebody to deposit gold on them.
    Last the contacts present a flat surface on one site and a round surface on the other site.
    Which is the right surface that goes in contact with the platinum pin?
    This particular may be important. The round surface will ensure a small contact area but the current density could be higher producing arcing.
    I could not remember their original orientation since the contacts were removed several times.
    I could not resolve this particular from the yahoo videos
    Are you able to see if the moving pin is damaged? I can make a macro picture if you think is useful. Do I need to put a new platinum tube on?
    Frank I have already done the test you mention and it looks ok. I am pretty sure the trouble is in positioning the gold contacts. I am not able to have the fingers to follow the bracket. They will not stay on the bracket. I am not sure if it is because the hole got larger. If I leave the pendulum to oscillate the gold contacts make the electrical connection some time and some time not or they will stay to long time. AS you know both of them cause the pendulum to stop.
    I can use a gauge from my lab to measure the distance ( 0,25 mm from platinum pin at rest position to bracket?)
    Unfortunately also the instruction went lost. Do you know where I can find them?
    The ATO was bought by my father during the fifty (in fact is the old version without transistor)
    Looking forward for your replies I thanks you in advance for your courtesy
    Francy
     
  33. Tinker Dwight

    Tinker Dwight Registered User

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    Does this clock have any kind of arc dampening device?
    Is it suppose to have a sunt resistor? Even a high resistance
    coil can cause arcing without something to take up the
    inductive spike when the contacts open.
    Tinker Dwight
     
  34. eskmill

    eskmill Registered User
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    No, the Junghans - ATO dry contact battery pendulum table clocks have no spark suppression device. The designer made no obvious arrangement to reduce spark or arc suppression that would have a deteriorating effect on the contacts. The ATO and Bulle battery pendulum clocks were both designed in France during the early 1920's by Leon Hatot and Favre Bulle with some collaboration by Maurice Lavet.

    I suppose that one could observe some back emf using an oscilloscope caused during contact opening. However, it is important to consider that the pendulum magnetic area is in motion within the solenoid during contact closure and opening on both the ATO and Bulle clocks which generates an opposing current. It may be difficult to identify any back emf from the voltage generated by induction.
     
  35. eskmill

    eskmill Registered User
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    #35 eskmill, Feb 5, 2013
    Last edited: Feb 5, 2013
    Francygh's excellent close-up snapshot of his ATO battery clock's movement showing the redundant gold tipped stationary contacts. One or both of these contacts are "touched" by a horizontal pin that is thrust toward the contacts by linkage from the pendulum motion. The contacts should be seen to flex just slightly during operation.

    In Francygh's picture, I believe I see a bit of wire extended from the back side of the moving contact lever. It may be a fragment of what should be a spiral "hair spring" necessary to assure that the moving contact is firmly connected to the battery circuit. Without the spiral hair spring electrical connection is only through the pivot bushings which is unreliable and insufficient considering the low-voltage and weak currents present in these clocks.

    I have attached below an enlargement of Francygh's photo showing what I suspect is a bit of the missing spiral hair spring wire.
     

    Attached Files:

  36. Tinker Dwight

    Tinker Dwight Registered User

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    Wow Les, you have good eyes.
    Tinker Dwight
     
  37. praezis

    praezis Registered User

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    Les, most likely you can say "HEUREKA"!
    Francy must now verify that the hairspring is damaged or missing.

    Regarding the contact assembly, it looks like the bracket is bent too much to the left. The adjusting screw moves that bracket, not the contact springs! When the lever with platinum pin is in rest position, the contacts must have the mentioned distance from the pin and they must rest on the bracket with mentioned tension.
    The pictures give no evidence that contacts or pin are bad. I would not concentrate on that primarily.

    I would doubt that ATO contacts do arc. Peak current is 0.5 mA only and the coil has no core. Attached are oscilloscope photos taken from a Brillie contact. Peak current here is 0.55mA. Back EMF is just 3V.
    Frank
     

    Attached Files:

  38. Tinker Dwight

    Tinker Dwight Registered User

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    Not much to arc there.
    I wonder if the parts have iron in the center and have become
    magnetized. That would explain the sticking.
    Tinker Dwight
     
  39. eskmill

    eskmill Registered User
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    For Francy and all. I have removed the movement from a Junghans-ATO battery pendulum clock similar to that shown in Francy's pictures.

    For what it is worth, the movement is very simple to remove. Unscrew the battery lead and remove the wire, then remove the two middle most fixing screws (they're long with fat shanks) and the movement falls into your hand.

    In the snapshot below observe the spiral hairspring pinned to the movement plate and with a collet on the arbor of the moving contact lever. The copper spiral hairspring assures continuity from the movement plate to the moving contact.
     

    Attached Files:

  40. Francygh

    Francygh Registered User

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    Once again, thanks to everybody.
    I attach the pictures below. I took them before last reply form Las how to remove the movement. In a couple of them I put the blade of a screwdriver to show that all the coils are in good shape. To the eyes of a beginner like me, the spiral hairspring looks to be in a good shape. Praezis It is good your explanation about the brackets and contacts removed one of my doubt. Yet I am not able to judge if the gold contacts lost their original flexibility neither if the contacts are mounted ok or should they present the round face to the platinum pin.
    The first two pictures are out of focus yet I think useful to judge the status of pin and contacts. Of course I can always remove the movement and take better macro.
    As loon as the ATO was at home I never saw spark or arcing.......
    Now that I feel to be closer to the solution I can't stand to read your replies.
    Francy


    DSCN4231.jpg DSCN4230.jpg DSCN4229.jpg DSCN4228.jpg DSCN4227.jpg DSCN4225.jpg DSCN4224.jpg DSCN4221.jpg DSCN4220.jpg DSCN4219.jpg DSCN4218.jpg
     
  41. Tinker Dwight

    Tinker Dwight Registered User

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    The spring looks to be soldered on. Is that regular? I'd have thought
    it was pinned.
    I don't think it is causing problems, just a little irregular.
    Tinker Dwight
     
  42. praezis

    praezis Registered User

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    Soldered or glued? Difficult to see. If glued, the task of the spiral was misinterpreted and there is no electrical connection.
    Correct, the brass pin is removed, end of spiral put into the hole in the stud and fixed again with the pin.
    Frank
     
  43. Francygh

    Francygh Registered User

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    I can always measure the impedance. Could you give me 2 good points where to measure it and I will let you know.
    Many thanks
     
  44. eskmill

    eskmill Registered User
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    #44 eskmill, Feb 8, 2013
    Last edited: Feb 8, 2013
    Francygh, you've already stated that you've made that measurement, "The coil is a 1450 OHM 1.5 volt and I measured with the voltmeter it is in a perfect shape."

    1450 Ohms is the correct DC resistance for the solenoid coil used in the Junghans ATO battery clock that has 12 teeth on the ratchet wheel. I've added a table from the 1965 parts catalog of a German supplier of clock parts. Of course, new replacement parts are no longer available.

    To clarify the means of attaching the copper 'hair-spring." It's not soldered. The long end is pinned to the movement plate and the short end terminates in a collet pressed onto the arbor pivot end of the moving contact lever.


     

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  45. Watchfixer

    Watchfixer Registered User

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    Can not do this glued on hairspring, this is the electrical connection from the movement plate to the lever for best low resistance connection. Redo that and you do have a tapered pin still present to reuse, need to clean up the hairspring and rotate the hairspring collet for light preload.

    Cheers, Watchfixer
     
  46. Tinker Dwight

    Tinker Dwight Registered User

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    Measuring may give you false reading through an oiled pivot if the spring is glued on.
    It needs to be properly pinned. It will work if soldered but that is a hack and should
    be restored to the correct mounting.
    Tinker Dwight
     
  47. Francygh

    Francygh Registered User

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    As far as I understand all of you agree that the trouble is in the non good electrical contact made by soldering. Provided I can remove the soldering without damaging the spring? how can I know how much is the light preload?
    Tanks to all of you!!!
    Francy
     
  48. Tinker Dwight

    Tinker Dwight Registered User

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    No, if it is soldered, it is a good electrical contact. Maybe
    even slightly better than if it was pinned.
    It is just that it should be pinned.
    If it were glued, then it wouldn't be any good.
    We just like to see clocks put together the way they
    were intended.
    Tinker Dwight
     
  49. WaldoLSX

    WaldoLSX New Member

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    hey guys hope you still use this forum im trying to fix one of these coil has the correct ohms i taped a 1.5 d battery in i have 1.5 volts i am missing the hair spring will the clock not run without it curious if thats the issue or the regular d battery im using wont power it thanks guys
     

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