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Seamaster 2551.80 question

  1. wndrful

    wndrful Oct 17, 2016

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    Actually the real question should be can anyone recommend for a good watch repair-person in CA.
    The question I am going to ask is what's wrong with my watch. :)

    I am a new owner of Seamaster mid-size 2551.80. I bought it used. Keeps good time. +/- few seconds a day.
    Since I am an engineer, technically-inclined and extra-curious I also went ahead and got myself a timegrapher (nothing fancy; ace timer).
    The watch stays in +/- 3 to 4 second range (mostly in +/- 2) with beat error of 0-0.2 and amplitude 260-330 range.
    However, when at the end of the day, when it is completely wound, I get large errors +300 to +400 sec/day and large amplitudes 335 to 340 or so. If I move the watch in vertical position, amplitude comes down a little to 330 and then watch is back to being accurate. If I wait for an hour or two, again the amplitude lowers and watch is accurate again.

    My surfing for solution led me to talk about overwinding and knocking etc. Is something like that happening here? Is it common for Seamasters? A major expense to fix it?

    An informed two cents would be most useful.
    So would be recommendation of a good watch repair guy in SF bay area would be helpful.

    Thanks
     
  2. Archer Ω 2

    Archer Omega Qualified Watchmaker Oct 17, 2016

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    Sounds like it's rebanking (or knocking) as you suspected. If you lay it dial up in the mic stand of the timing machine, and watch for it to start rebanking at full wind, without moving the watch put your ear to it to see if you can hear it ticking - if you can hear it, you may notice it sounds a bit like a horse galloping.

    It will sound like this, but may be hard to pick-up...



    Causes can be a mainspring that is too strong, too much braking grease in the mainspring barrel, or a few other obscure items.

    Rebanking is too much amplitude causing the balance to turn so far that the impulse pin strikes the outside of the pallet fork horn, and the balance rebounds faster that the balance spring would normally return it. It them goes too far in the other direction, and keeps bouncing back and forth - this leads to a very fast rate.

    By turning the watch to a vertical position, you increase friction on the balance pivots, lower the amplitude, and the watch stops rebanking.

    Cheers, Al
     
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