Service: Seiko 6309-729A

IMG_9693Ben sent me this rather sorry looking Seiko 6309-729A. The day dial is stuck somewhere between days, there is a lot of dirt on the dial, and it’s running way too fast. Well, that’s what I’m here for!IMG_9694

This looks wavy, and we have a huge beat error. The amplitude isn’t that bad for a Seiko.


The crown gasket has disintegrated, and the black remnants of it are around the pendant tube.IMG_9699

I can already see why the day display isn’t working – see where it says “ring upward”? Yes, that ring is mounted the wrong way around. IMG_9707

Time to take everything apart. The balance cap jewels are completely dry, and have some white opaque dirt on them.IMG_9716

A fair amount of dirt all around.IMG_9718

The old mainspring.IMG_9719

As usual, everything gets cleaned.IMG_9722

The crown with the old and new gasket. You can see how badly worn the old gasket is, the inside diameter is way bigger than on the new one. All that material was wrapped around the pendant tube.IMG_9723

The crown with the old gasket.IMG_9726

The new mainspring has arrived as well.IMG_9727

And I can start putting the movement back together.IMG_9729

Ticking again.IMG_9731

That’s a lot more regular, and I will make a final adjustment once the watch has run for a day.IMG_9732

The auto winder ready for assembly.IMG_9733

And the top plate is back together.IMG_9734

Now for the bottom plate …IMG_9736

You can see the little circlips now being mounted the right way around.IMG_9737

I case the movement, and put a new back gasket in.IMG_9738

That looks a lot better!IMG_9739Lovely watch.


23 thoughts on “Service: Seiko 6309-729A

  1. with due respects christian,Ihave been repairing seikos for 20 years the c clip was in the right way round in the first place,

  2. Dear Sirs and Madames,
    I have a problem with my Seiko 6309-729A, the day of the week and the date can only be changed manually and are not adjusted automatically.

    Sincerely yours
    Helmut Teng

  3. Pingback: Advice Needed: Seiko 5 Complete Overhaul - Page 2

  4. Have a Seiko 6390-7049. Had it serviced by Seiko authorized service center. Gaskets are not available for waterproofing. Do you use aftermarket gaskets?

  5. Christian,

    I bought a Seiko 6309-729A off the internet and it kept great time for a year as long as I was wearing it, but doesn’t store energy and my winder doesn’t keep it charged either. I was told by a local watch shop it needs to be serviced. Can you provide an estimate for servicing this watch?

  6. Sorry to nit pick, especially so long after, but as a 729A this should have a Pepsi bezel insert as the 7290 was the one with black. It was probably replaced at some point and the person replacing it only had access to black bezels or the back is from another watch.

    Can you explain what is wrong with the circlip in the first picture of the date wheel as I can’t seem to see much difference?

  7. Hello: Superlative craftmanship!!!. Iยดd wish you were closer. I have many Orients 46941/43 and ETA 2824-2. I have read thousands of pages comparing both. All are working very good for me for a very long time. I learnt now that EtA 2824-2 has more amplitude and of course 28800. Technically more amplitude and more beats convey more precision but a more wear? I am an engineer and it came to my hands a study where Eterna/Eta winding system is >2% more efficient than Seiko//Orient IWC Pellaton based “magic lever” with scientific calculations. May I presume that, technically, ETA is more capabable? Both movts are very well engineered indeed. Btw, almost all new Seiko/Orients that says “Japan movt” that are sold in the Americas come from thweir factories in Amazonia, Brasil. I thank you from Patagonia, Argentina.

    • Hi Sergio,

      Yes, the ETA movements with the higher amplitude and higher beat rate are more accurate. All Seikos suffer a bit from low amplitude, and that seems to be a construction feature. I think reliability was more important to Seiko than precision.
      The funny bit is that the ETA movements are very hard wearing as well, e.g. don’t have more wear even though they beat faster and have a higher amplitude. Technically, I find the ETAs far superior to the Seiko movements. Performance counts. At least for me ๐Ÿ˜‰

      I have a customer in Uruguay, so Patagonia can’t be too bad in terms of posting a watch!

      All the best from sunny England,


      • Hola Christian: Thank you!! after months of investigating now I understand well. Yes, my brazilian Orients and Seikos have an error of 7/8 s/day and one Orient is 39 years running really good (10 s/day) with no service…(I found it months ago and surely it needs service) so they privileged reliability… I have read almost all the web that magic lever was so efficient but scientifically is the Eterna system by a small %. The famous video Orient vs Eta is incomplete, I presume. My Hamilton 2824-2 Limited edition for the Argentine Independence is fast 8/10 s/day but consistently (it is OK I guess..) I have ETAs 2788 (ancestor 2824?) still running very good since 1971 and I was tough with them at school.. My great grand-Dad was born in Uruguay…we were the same country…One can post watches in your blog? (forgive me I am ignorant). Regards from still frozen Patagonia…;)

  8. Christian,

    How long does it usually take to disassemble and assemble a watch, for those that know what they are doing and no need for any custom parts?

    How long does it take to learn how to do it?


    • You can take a 5 day course at the BHI which gives you the basics – enough to start servicing your own movements at home. Once you’ve done the first 100 movements or so, you will get up to speed.

      An automatic day/date takes a good 4 hours to service.

      Best regards,


      • Didn’t expect it to be so short a course. I can well understand the experience effect of 100 watches. It would probably be a 1000 for me!


  9. Wow Christian, the old Seiko has been given a new lease of life!

    As a watch amateur it took me a while to see the difference of the c-clip on the day/date wheel photos but I saw it in the end. By the looks of some of the scratches inside and on the date wheel it has had someone tinkering around in there who shouldn’t have been I guess!

    I have one last favour to ask! On all of your blog posts I see the photos of you measuring the beat/amplitude of the watch – can you explain this in easy to understand detail? I keep looking at the device and trying to work out what all the wavy lines mean but I’m struggling!

    Thanks again, you offer a brilliant service which is rare these days, I am delighted. The next one for you in the Rolex Date, I’m already looking forward to seeing the pictures of the movement as it has never been opened up since I’ve owned it!

    Thanks again,


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