Service: Tissot SeaStar calibre 783

John sent in this Tissot for a service. The crystal is quite scratched, and the watch isn’t working at all, even though it’s fully wound.

Time for an inspection!

The “USE KEY…” on the back is the hint how to get into this watch. The back is solid, so doesn’t open. The only way in is through the front.

With the glass removed and the winding stem taken out, the movement comes out of the case. No case screws, and the case ring rests in the case, so something is wrong here.

Inside the red circle is a case screw that has fallen into the hairspring.

There is the case screw, happily sitting on the pallet fork bridge.

Clean looking movement.

All is well on the bottom plate, too.

I start off by putting the balance jewels back together and oiling them.

Then it’s time for a new hairspring.

The hairspring got damaged by the screw, and that in both vertical and horizontal direction. As a new balance with hairspring is £20, I take the easy way out and order a new one, rather than sweating an hour over the old, bent one.

Nice looking movement in good condition.

And this is rather good looking, too!

The hands have seen rather a lot of bending and messing around with, but considering the state of the dial, they fit together.

I fit a proper new crystal (with a tension ring) as whoever serviced the watch last put in a normal acrylic crystal without tension ring.

The bracelet gets a proper clean – nice watch!


Roger asked me to upload a photo of his Tissot, and I can’t post photos to comments, to I’m putting it up here (see the discussion thread below).


14 thoughts on “Service: Tissot SeaStar calibre 783

  1. I realize that this is an old post but I’m commenting in the hopes that you might see this! I’m currently looking at working on a Seastar with this same movement. It is not in as a nice a shape as this one though. The first thing that struck me was a sloppy rotor. Both shaft and rotor bushing appear to have suffered quite an amount of wear. I’ve tried to locate spares but only found the rotor shaft so far. I also noticed that similar rotors that I’ve found for other calibers in the same series appear to not be provided with the bushing in place. I’ve tried to find a labeled parts list for this movement but I’m not sure what part number the bushing has, if sold separately. If you would care to shed some light on this, and where I might find it, it would be deeply appreaciated!

    Best regards

  2. Hi Christian,

    You’ve done a nice work on your Tissot. Would you do that for my Tissot Seastar Automatic (1959) as well? The watch is still running, but the watch is dirty inside. I guess with a nice little cleaning bath the watch would run great again. Let me know and if you would, how much it would be.


  3. A very simple and elegant dial, one of my favourites !……
    I have a Tissot Visodate of a similar vintage, I assume that it is the same assembly as above but with a date ring. I need a new date wheel as the paint is flaking on the one I have.
    I now have the crystal off, hands off and the dial off, for access to the ring…. bit stumped now as I can’t see the button for the stem, so I can’t get the movement out to find the number to order a ring..etc. etc. …… any pointers ?

  4. Hi Christian,

    I have the same Tissot 783.1 caliber (Seastar automatic) but when manually wound it keeps winding for ever… . There’s tension on the mainspring (not broken), is this normal, some kind of slipping/safety for overwinding? I opened up the barrel and there’s a lot of grease, maybe to much in my opinion…?



    • Hi Jelle,

      That is as it should be. All automatic watches have mainsprings that start slipping once they are fully wound.

      If you listen carefully, you might be able to hear the slipping.

      Grease in the barrel is no problem as long as it doesn’t leak out.

      Best regards,


      • Thanks!

        I cleaned the auto winding assembly and it keeps time and beats pretty good now (don’t have a timegrapher), only when held in one particular angle it stops beating… a broken balance shaft??? I can’t see anything moving or touching another part.



        • That could have several reasons – the hairspring could be touching the balance or balance cock in a certain position, or the roller could scrape on the bottom jewel, or the balance staff is broken as you suggested. Check all these things out with a 10x loupe and hopefully, you will find the culprit.

  5. I don’t think it is unreasonable to buy a new component for £20 if you think it will take an hour to fix the old one, and really – could you guarantee to be able to or that the fix would be 100% as good?

    I do like Seastars… am wearing mine today that you repaired for me a few months ago 😉

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