Service: Omega Chronostop calibre 920

IMG_1356We’ve already seen the Chronostop with the 865 movement earlier. Charles sent this one in for a service. It does look like it could do with a bit of TLC, so let’s administer that.IMG_1359

The top plate of the 865 and the 920 are identical, as the difference is the date on the bottom plate.

IMG_1360The movement can do with a service; the amplitude is rather low.IMG_1362

One of the case clamps is broken, but I can find a new original one.IMG_1366

Time to take the movement apart.IMG_1382

Under the chronograph layer is the wheel train.IMG_1383

The usual dirt.IMG_1384

Check out the mainspring – somebody shortened a broken mainspring and bent a hook so it would stick to the barrel.IMG_1385

Now for the difference – the 920 has a date display.IMG_1391

The chronostop movement is pretty complex, and has almost as many parts as a proper chronograph.IMG_1450

That looks better than the cobbled together old mainspring.IMG_1452

I start off with the wheel train.IMG_1454

And the base movement is ticking again.

IMG_1495Now that’s better!IMG_1460

Now it’s time for the chronograph layer.IMG_1462

The bottom plate ready for dial and hands.IMG_1499

The second hand had a split tube, but I managed to find a new one, and everything is working again as it should.



16 thoughts on “Service: Omega Chronostop calibre 920

  1. I have inherited the same model of watch which as far as I know has never had a service.
    Its working well but I think it would benefit from a service.
    Could I send it to you?

  2. I am also working on this watch. Each time I take out the crown and stem, the winding pinion keeps coming out. I noticed this when I put everything together, I could never wind the watch. Thanks for your help 🙂

  3. Hi Christian,
    What is the part number for the case clamp?
    I have the same watch and one of the clamps is broken as well. Is it a common issue?
    Thanks in advance .

  4. Hi Christian

    always an interesting service report to read,
    and useful, in many cases.
    However, the lift angle for this Omega caliber should be set to 50º, instead the 52º.
    Thus, its real balance amplitude is a bit lower than the one showed in the screen.


  5. I also like these Omega models. The driver is quirky but I would be very much happy to own one of these.

    I keep watching them also but they have really got a little more expensive of late, has also the Dynamic model.

    Lovely watch.

  6. Hi Christian!
    I just found this blog recently and I´m allready totally hooked!The volume of material and how much one can learn her is really awesome.Keep up the good work and variety of brands.
    Cheers from Germany
    (who´s Bell-matic has only an amplitude of 200, but now know´s that this is ok…because: Seiko)

  7. I am very grateful for the thorough work carried out by Christian. Having worn this Chronostop virtually everyday since purchasing it in, was it 1970?, I do not appreciate switching to another watch. It’s a particularly useful size for a man with a small wrist.

  8. I love the Chronostop… was watching one on eBay the other night but fell asleep before the auction ended – and it went for less than I would have paid for it. Damn sleep ;(

    Does a shortened mainspring have any impact on the amplitude? I would guess an amount of shortening would only reduce the total capacity of the spring, but too much would start to reduce the force it could develop…

    New crystal as well – can see the logo on the new one but not the old one. It is amazing the difference a new crystal makes 😉

      • Hi, I am working on a project watch right now that is a Chronostop with an 865, it is in need of an hour wheel, I can’t seem to locate one for an 865 but I found one brand-new for a 920 are they interchangeable? If not would you know the part number that I’m looking for …I can’t seem to even find a diagram that shows all of the parts with part numbers.


Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.