Service: Omega Seamaster calibre 1120

Vincent from the US sent me this Omega for a service. It took a couple of months to get here, getting rejected once from the UK as I never got the notification card to pay VAT on the watch. Second time around, and £29 later (for VAT and processing fee), it’s finally here. So if you send me a watch from the US, please declare no value as I will have to pay VAT otherwise (which I will have to slap on your bill).

The watch doesn’t work at all, so let’s see what is going on here…

Under a dust cover, the Omega 1120, which is actually an ETA movement 😉

I remove the auto winder assembly before taking the movement out of its case.

The gear train.

All parts ready for the cleaning machine.

A new mainspring goes into the barrel.

Bottom plate reassembled.

Starting to put the top plate together.

When putting the balance in, I notice a very small amplitude and have a closer look. The hairspring is touching the balance, and that’s not good news. I readjust the position of the hairspring, and put it back in.

And the movement is ticking happily.

Dial and hands go back on.

… and back into its case. Lovely watch!

With a great performance. Never diss an ETA movement 😉

19 thoughts on “Service: Omega Seamaster calibre 1120

  1. Could you make the same repairlist for the Omega speedmaster cal 861 , I would apriciate very much. Thanks on beforehand, Vitus Gottlieb.

  2. Hello Christian,

    I enjoyed reading your description very much, and found it to be very informative. I recently had my SMP cleaned and serviced, and was given a sheet listing the following amplitude readings: 281, 263, 244, 228 from the cleaning. Please tell me what these mean, and whether or not they are witihn the 1120 precision tolaerances. Also, how would these affect time accuracy? Thank you. Rob.

    • Hi Rob,

      That sounds pretty reasonable for an amplitude. It tends to go down in vertical positions, so that’s normal. 228 might be on the low side, but it’s still acceptable. I don’t think there are specific amplitude tolerances for your movement. The amplitude itself doesn’t say much about the accuracy of the movement – it’s the change of beat rate in the different positions that does.

      • Thank you very much, Christian. That is helpful information. I am curious, though, as to which is the beat rate, as shown in the picture above. Is it the rate indicator or the beat error that represents the beat rate? The rate on my sheet ranges from +.003 to +.000 at 0H (presumably this represents zero hour), while the range is +.004 to -.002) at 24H. Does that reflect the change of beat rate, and if not, how can I find this out? Again, thank you for your patience in explaining these things. Rob

  3. Hi Christian ,,, exellent work,,,
    sorry Im from Argentina and I have an Omega Seamaster with this movement… the Watch is beautifull,,, Mi Watch is now Slow -10 seconds/day… realy I want to know is for a little adjustament is move the screw a veeeery little to the + position… sorry i ask you this because in others movements are different, there are not these screw…there are a little leg in the opposite place,,, there is a small leg is pushed more or less away from the mobile point, the leg is in the opposite point on the spiral… near the static point

    • Hi Eric,
      Yes, you can adjust the movement by turning the regulator screw a bit towards the + position. But there will be a reason why your watch is now slower, and the reason will be that it needs a service. So my guess is that any adjusting will only be a short term solution.

      • thanks for answering Christian … has been very friendly …
        if it can be possible that they may need a service … but so few seconds that I would like to try to fix … in here really i do not trust anyone,,, there may be some compatriot that offend but in here is all wrong, all… and I do not want to ruin anything … is the trust
        thanks Christian

  4. Hello Christian. I’ve had a SMP for 15 yrs and given faultless service. I had it fully serviced and polished at omega 2 yrs 3 months ago at Swatch however it’s been stopping intermittently of late. Swatch say as it’s gone over 2 yrs is not covered on warranty now, no goodwill either! What sort of lead time are you working on at the moment for something like this? Best, Pete UK.

  5. Very good and informative review… always.
    I am the proud owner of a 2000 sea master 1120 in pristine condition,black dial.
    My grand father was an omega retailer,in Vichy,France,and my uncle Christian was a talented”horloger”,graduated from Geneva.
    At a later age I have the feeling to pay a tribute to a great legacy wearing an omega,I will keep reading you and certainly will require your services if my precious sea master is ever in the need.from Houston,texas,Philippe.

  6. I just purchased one of these Cal 1120 seamasters from a vintage watch shop. It works fine once I wind it and keeps perfect time for about 40 hours, then just stops ticking. I suspect this is related to the automatic winding mechanism being non-functional.

    Any advice?
    Any ballpark idea on cost to repair?

    • Hi Jon,

      Yes, that sounds very much like the auto winder isn’t working. It’s hard giving you an estimate as I really have to check first if anything is broken. Best case, I take apart, clean, and put together and lubricate the auto winder, and the problem is solved – that will cost around £25. If we need any parts, you have to add that to the bill.


  7. Hi Christian,
    Fantastic in depth look at the 1120. As usual your attention to detail is faultless.
    I was wondering about the ETACHRON adjustment lever that I see (from the photos) was right over to the + side when you got this watch but you have rebuilt and set it back at the half way mark. I have put mine to the furthest + mark to speed the old girl up a bit but I’ve read this is not advisable.
    I was wondering if you’d share your thoughts about this aspect of the 1120.

    Kind regards,

    • Hi Jim,

      The regulator should be in the middle position – if not, it’s normally a sign that the watch needs a service. You won’t break anything putting it into the furthest position, so don’t worry about that.

      By moving the regulator directly and not through the adjustment screw, you can adjust what the middle is…

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