Service: Tissot SeaStar calibre 784-1

Another day, yet another SeaStar! This one is from our very own Cirrus, the most prolific commenter on this blog.

The watch isn’t working, and there is a good reason for it!

A little hint here – you can’t remove the case back ๐Ÿ˜‰ Looks like various people have tried, and to no avail.

This is the only way in.

The dial isn’t screwed down properly, and just lifts out. Also, there is no hour wheel, and no pawl or pawl spring.

Quite a bit of dirt here.

Having a look at the minute wheel, I notice that half of its teeth are missing.

Normally, the watch would be beyond repair – just the parts to get this right would be more expensive than the value of the watch. But to the rescue comes a client of mine, Earl, who recently sent in a 784 to replace the date ring on his Tissot. He kindly donated the rest of the movement, and I’m passing his generous gesture on to Richard. Any parts movements I get given by clients are marked as donated, and I pass parts from those movements on for free – just to encourage others to show the same goodwill. Just got a donation of a Chinese fake movement today, and I’m sure I will be able to put that to good use one day!

Bottom plate almost cleared – just the setting mechanism and the balance jewel to go.

Reassembly starts with the balance jewels.

Top plate complete and ticking. Great looking movement, and clean again!

Now I adjust beat error and beat rate.

With the donor parts, the bottom plate comes back together.

… and we have a working bottom plate again.

Ready for the dial and hands.

Ready for the crystal.

Great looking watch – and ticking again!

16 thoughts on “Service: Tissot SeaStar calibre 784-1

  1. Hi Christian! I believe this is my second comment in your site but you have to know that Iยดve been reading it for a while now. In fact, this site is the main reason why I am starting to get involved in the world of watchmaking, thanks to you.

    I am working on a Tissot Seastar very similar to the one published here but with a 794 movement, the problem is that the hour wheel is misssing and I would like to know if you could tell me if the 794 and the 784 hour wheels are just the same, Thank you very much!

  2. Hi Christian,

    Wow, its amazing what you can achieve with a little (lot) knowledge. I have a Seastar Automatic – sure its a 784 from the pics – are you repairing these professionally, if so would you be able to get in touch please?
    Regards Simon

  3. Hi Guys

    I am having an issue regarding the 794 movement, my hour wheel has numerous teeth missing and am trying to obtain one, the 784 is only 1.50mm, the 794 is 1.95mm and that is the one i need,after ordering the 784 hour wheel i wasn’t best pleased, can anyone be of assistance?

  4. My wife purchased a Seastar circa 1978 watch for my birthday but the strap is too tight. I have sent it to Tissot but they say they hold no spare links for it. Is there any posability you could be my last hope

  5. I have a similar movement tissot 794, and I would like to know how is the day disc spring (ref 2575) installed.I could not see any picture of it.
    I would like also to know how to find the correct position for the wheel changing the date, to avoid snapping teeth on the minute wheel

  6. Hello Christian,

    Can you tell me how to take the winding stem out of this caliber.
    I have the same and would like to clean it.

    Many thanks,


    • Hi Pierre,

      You can carefully lift the set lever,which is accessible next to the date dial, with a small screwdriver, after removing the dial.

      Best regards,


    • This is actually the 2nd Seastar of mine that Christian has repaired… the other was a 1974 2571 which I think is my favourite watch now ๐Ÿ˜‰

  7. Very interesting post! Could I ask two questions, please? 1) any guess what could cause that kind of damage to the minute wheel? 2) how do you normally go about if the crystal does not want to let go (due to glue or whatever’s stopping it from giving in when you compress it with the crystal lift … )?



    • The damage was caused by forcing the setting mechanism. If you mount the wheel driving the date changer in the wrong position, it blocks. Trying to advance it will cause that sort of damage.

      So far, I have been lucky and able to remove all crystals that way.

      You could glue something to the crystal with superglue if you can’t get it off with the lifter…

  8. Clearly you get what you pay for in life, and this cost me 9 Swiss Franks I think! There was no mention of missing bits in the auction… although it was in German so maybe I just missed that part.

    Don’t know if there was any evidence of it, but I had a go at removing the crystal before concluding it was glued in and deciding to let someone smarter have a go. I assume there was a tension ring?

    Many thanks to Earl for donating the movement; I am sending a few movements Christian’s way to balance out the Karma a bit… including a (presumably) Chinese auto now I think of it ๐Ÿ˜‰

    Thanks also to Christian for another superb job and speedy turn-around – and great photos of a movement I will probably not get another chance to see!

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