ETA 2894-2 Chronograph hand adjustment

Discussion in 'Watch Repair' started by oilseed, Apr 11, 2017.

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  1. oilseed

    oilseed Registered User
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    Sep 27, 2009
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    I've recently completed the disassembly and re-assembly of both the movement, auto wind mech and chronograph module.
    Being this is my 1[SUP]st[/SUP] time, attempting this endeavor, it was quite an interesting challenge. I realize that 'ETA' discourages
    anyone from disassembly and re-assembly of the chronograph module, but it was something I could not resist.
    (glutton for punishment I guess).
    Anyway, the watch is back together and functioning properly (to a point and this is where I need expert advice from those who have worked on the 2894-2).

    Following the ETA tech guide.pdf, I installed the "second counter hand" (what most of us call the sweep second hand) and then followed the procedure to test the repeatability on hand alignment.

    • Step 1
      • Start chronograph
      • Let run for 5 sec
      • Stop chronograph
      • Reset to Zero (or 12 position)
      • Repeat 2x
    • Step 2
      • Start chronograph
      • Let run for 20 sec
      • Stop chronograph
      • Reset to Zero (or 12 position)
      • Repeat 2x
    • Step 3
      • Start chronograph
      • Let run for 35 sec
      • Stop chronograph
      • Reset to Zero (or 12 position)
      • Repeat 2x
    Result of the testing:

    1. The 5 second test was flawless. Both cycles rest the 'second counter hand' to 12.
    2. The 20 second test was also flawless. Both cycles rest the 'second counter hand' to 12
    3. The 35 second test failed. On the 1[SUP]st[/SUP] attempt, the 'second counter hand' reset to 12:02 (2 minutes 'past' 12).
      Meaning the hand did NOT return all the way to 12. This was quite strange to me, as if anything, I expected
      (if the hand was not seated on the post firmly, that the torque of the hand swinging all the way back to 12
      (more than 180deg) would move the hand 'beyond' 12 (and leave it at 11:5ish).
    I then suspected the 'cam' adjustment screw? (not sure is this is the correct terminology). Here is the picture.
    [​IMG]
    Picture with chrono module top plate removed.
    [​IMG]
    Does 'this screw' (circled in RED) 'adjust' the hand position for proper return? Sort of a fine tuning cam?

    The ETA technical guide does NOT provide details of how to correct a 'failure' for a given test. They just say "here's the test and if it passes you're good." But if it doesn't? no info.

    Also, for the 'Minute Counter hand' and 'Hour counter hand';
    The instructions say;
    "Minute counter hand: testing of
    return to zero"
    "Start chronograph (pushbutton A),
    then stop (pushbutton A). Using a
    pin, advance the minute counter
    hand to the 10 minutes position.
    Reset to zero (pushbutton B). The
    minute counter hand must return
    exactly to the 30 minutes position"​

    what does the term "USING A PIN' mean? Are they (ETA) implying that the watchmaker PUSHES the hand faster than the watch gear is moving it? So he can test it? Really? Is this gear 'clutched' in some way as to prevent damage to the gear or pinion if this is performed?
    I'm hesitant to do this and rather wait the 10 minutes, until the hand reaches its position before reset.
    Any opinion on this?

    Thank you
    Bill
     
  2. karlmansson

    karlmansson Registered User

    Apr 20, 2013
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    #2 karlmansson, Apr 11, 2017
    Last edited: Apr 11, 2017
    If you reset the watch at 35 past the hand will travel back in the left side on the dial. So that the hand moved past 12 and stopped at 12.02 makes perfect sense with your poorly fitted hand theory. Usually chronographs have "hearts" that the reset hammers will push on. Depending on which side of the heart the hammer pushes on the hand will return on one side or the other.

    I mostly work with mid 1900s watches so this is a bit of unfamiliar territory for me. But in most standars chronos the center seconds wheel has a finger that will advance the minute counter wheel once a minute. So it only makes contact with the actual going train for a few seconds to the minute. So yes, they are implying that you can advance the wheel faster than the watch itself. Usually the minute recording wheel is indexed my a minute recording jumper. A very fine spring with a "club" on the end that rests between the teeth of the wheel, making sure that the wheel does not move when it shouldn't. The force of this spring is easily overcome but care should be taken not to damage it. As all parts of course but they are usually extremely delicate.

    It sounds like you need to familiarize yourself a bit more with how chronograph movements work before you attempt adjusting them. The excenter in the picture has nothing to do with centering the hand. The excenters are there to limit travel of the different hammers and levers of the system. Also depthing between gears. The centering of the seconds hand relative to the minute recording wheel is adjusted by moving the hearts. But in your case I think its just not on there firmly enough. The hand that is. A good rule of thumb is to not touch the excenters unless there is a problem.

    Best of luck!
     
  3. oilseed

    oilseed Registered User
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    Sep 27, 2009
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    Meridian, Idaho
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    Hi Karl,

    thanks for the reply. good info.
    so I guess the only way to recenter the hand is to remove and reset it on the pivot. maybe to also recheck and refit the tube (a bit tighter) before the install.
    this will ensure if has a firmer grip. is this what you were implying?
    I know this is the procedure on the older column wheel chronographs, but this newer model, maybe (for sake of production) ETA incorporated a 'fine tune'
    feature for the production department?? just a guess. that's why I asked.

    This follows the thought process ETA employed making the 'chronograph module' unrepairable (not offering any spare parts).
    Their recommendations to service departments and watchmakers was 'remove and replace' no service.

    regards
     
  4. dAz57

    dAz57 Registered User

    Dec 7, 2011
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    I don't particularly like these added chronograph modules, you get anything up to a two minute error if you set the time in the wrong direction because of the amount of backlash.

    I have done a few of these and no I have not pulled the chronograph module apart because I didn't see any need for it, from what I can see there is very little adjustment in these, and no adjusting that eccentric won't fix your problem.

    Most likely the seconds recording hand is not tight enough.
     
  5. Paul_S

    Paul_S Registered User
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    Mar 27, 2015
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    This is an interesting series of posts. I have been curious to see what the ETA chronograph module looks like.

    There's something sad about a "just replace it" module that shouldn't be serviced, especially when it is used in some expensive watches.
     
  6. dAz57

    dAz57 Registered User

    Dec 7, 2011
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    I've had them in some models of Breitling although most use the 7750 or variants, Longines use it, if you look along the crown and pushers of a true chronograph you will see they are in line, with the module added to the front of the movement the pushers are a bit higher than the crown.

    As I said I don't like it, I prefer a real chronograph, and thanks to Swatch's policy good luck in getting a replacement module.
     
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