Service: Omega Seamaster calibre 1120

IMG_9994Jon from Ohio sent in this Omega. It’s having problems with the auto winder, as it’s fine when manually wound, but it will stop if only worn and not wound.

This Seamaster uses the calibre 1120 movement, which is an ETA2892.2. A great performer, and a reliable movement.

To get to the bottom of the problem, I don’t really have a choice but to do a full service first, as I won’t be able to exclude components bit by bit from my quest to find out what’s wrong…


The Seamaster has an antimagentic dust cover on the back, and we’ll get to that later.

IMG_0019The rotor sits under the antimagnetic cover, and is nicely decorated.


The gears of the auto winder.IMG_0027

Dial and hands.IMG_0029

And the very neat bottom plate of the 1120.IMG_0034

Once the auto winder bridge is off, you can see that the gear train has a cock, and not a bridge. A single screw holds the top jewels for the third, fourth and escape wheel.IMG_0038

The barrel and centre wheel – it isn’t really a centre wheel, as it’s off-centre, so I should call it the second wheel.IMG_0039

I will put in a new mainspring, as I have to exclude all other causes for the problem.IMG_0040

All ready for cleaning.IMG_0041

Everything ready for assembly, with the usual suspects epilame treated.IMG_0042

The auto winder gears come back together.IMG_0083

The keyless works are back on the plate.IMG_0084

And the bottom plate is finished.IMG_0085

The new mainspring has arrived.IMG_0086

And I put it into the barrel with a bit of mainspring grease.IMG_0087

Everything ready for the barrel bridge.IMG_0089

Barrel bridge with click.IMG_0090 IMG_0091The basic movement is back together. Jon asked me for a video of the movement ticking, so here it is. Jon pointed out that in the background, U2 is playing “I still haven’t found what I’m looking for”. How fitting 😉


The base movement performs really well. IMG_0096

Everything is back together, and I’m ready for casing.IMG_0098

Dial and hands go back on.IMG_0099

And I case the movement.IMG_0100

The dust cover goes back on.IMG_0101

And I test if the watch is waterproof – it is indeed.

Now comes the painful part – after having wound the watch fully, I put it in the autowinder, and it stops duly after 46 hours. That means the auto winder still isn’t working.

After scratching my head for a considerable amount of time, I take the dust cover out, just because I can’t think of anything else causing the problem. With the movement almost completely unwound, it does 24 hours and is still happily ticking when I take it out. So I have found my problem!

Now I take my case press and every so slightly press out the dust cover, and put it back on.

7 days in the autowinder later, and I’m happy 😉


16 thoughts on “Service: Omega Seamaster calibre 1120

    • Yes, that’s possible. Please keep in mind that such modifications devalue a watch, so once it becomes vintage, it could be an expensive decision to have something like that done.

  1. Hi,
    My Omega Seamaster Pro (2002), has a power reserve of 48 hrs when I manually wind. But in a 12 hours hand worn situation it shows a power reserve of close to 31hrs. Is this normal ?

  2. I have seen a few of these 1120 movements with the same problem and while deforming the anti-magnetic cover is a cheap fix, the actual problem is wear to the rotor bearing. The bearing wears, causing the rotor to swing outside it’s normal path and touch the anti-magnetic cover. Replacing the rotor bearing solves this problem. This post has some nice photos of the wear ring caused on the inside of the anti-magnetic cover;

  3. Could you please tell me how to take off this antimagnetic/dust cover? Is it screwed? I don’t want to make any damage to my watch. Do I need any special tools? I want to write down all the ref numbers etc. Thank you in advance for answer.

  4. Thank you for the thread !
    I have the same omega cal.1120 since 2002.
    I wear it on and off , few years back the time adjust stop working and the stem came out without stopping .It was still running ok and I had to rely on a watch winder. Few weeks ago , it finally stopped working . Shake it, rotate it and …. it just refused to turn !
    May be it is the reason as what you discovered , hopefully !

  5. Clever detective work… and really nice blog entry. My son and I perused all the photos today. we love seeing the inner workings of my watch. Can’t wait to get it back. Great job!

    I think I will have some more work for you soon maybe.

  6. Lack of box and paperwork always makes me wonder at the possibility the watch might be nicked though; I guess pawnbrokers and the like ask for proof of identity before handing over any cash, but still…

  7. Nice deduction… or was it a reduction?

    I saw this exact model in the window of a Pawnbrokers in Mold last Friday and actually got as far as asking to try it on before discovering it had no box, paperwork or the removed links. It was an OK price if these had been present, but not without so walked away ;(

    • Mold North Wales?? I live not too far from there and occasionally work there! Out of interest how much was it!??

      • Yup – North Wales.

        Not a pawnbroker as such – more a CashConverter type shop on the street where the market is, and it was a grand.

        I live about 20 minutes away, but rarely visit Mold!

    • More of a reduction I’m afraid – that’s why I did a full service first, and then took it step by step. It’s always the fully wound power reserve first to make sure the movement is fine, and then you can move on to the auto winder for troubleshooting.

      And yes, without papers and box, you expect a 25-30% reduced price tag, as you are taking quite a gamble. It tends to be those watches that have problem later, as they have gone through quite a few hands. I’d say well done for walking away 😉

      • I wouldn’t have bought one off eBay or similar for that price without all the bits… but once I had seen it I was still quite tempted 😉

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