Service/Repair Eterna 520 H


Today it seems bigger is better, but it has not always been this way. In the 1930’s smaller was seen as more of a technical achievement as people where used to large pocket watches. This Eterna is 31.3mm but has quality to it without being flashy. It tells me the time and then disappears under the shirt sleeve. It also has one of my favourite movements the Eterna calibre 520. This one is not running and has a worn upper barrel arbor hole.


The upper barrel arbour hole is quite worn, it’s not visible in the photo, but you can see the mark on the barrel where it has been scraping gainst the bridge.


Early 40’s style shock protection.


The movement coming apart.


Old mainspring.


Setting/winding mechanism.


I have cleaned the movement.


The balance staff was bent, so I fit a new one.


I see the new balance staff moves freely.


New mainspring in the barrel.


New barrel bush in place.


Movement coming together.


Setting/ winding mechanism back in place.


Movement back together and ticking.


Now a major problem being the balance is too light and the watch is gaining a lot of time.


I add balance washers to the balance screws, this adds weight and slows the balance down, when I’m close to the correct timekeeping I poise the balance. This operation takes some time, but its good to practice.


After some trail and error I hit the mark;)


Dial and hands back onto the movement.


Movement goes into the case and looks good.


Very nice looking classic.


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5 Responses to Service/Repair Eterna 520 H

  1. matabog says:

    31.3mm? That looks realy good on your wrist!

    p.s. would you be so kind to make some sort of work instruction for rebushing the barrel bridge? I think it is a pretty common issue for an old watch.

    Liked by 1 person

  2. andrew says:

    I’m interested in the fact that you needed to adjust the balance after replacing the staff. Why would it be lighter if you were replacing a like for like balance staff? Would the new staff be made to different specifications? 663 sec/day is quite a significant variance


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