Seiko 7123-823B Quartz

This Quartz powered Seiko Sports 100 came in recently to have a problem with the crown and seconds hand looked at, it also was in need of a service. Like many quartz calibres it’s probably never had one in it’s life and it certainly needed doing.

Seiko 7123-823B

The back of this watch doesn’t have the more usual Seiko tsunami logo, it’s a rather stylised wave version on this one. This is because it’s not a divers watch, Seiko divers are water resistant to 150m minimum and carry the tsunami logo usually on the caseback but also on the rubber strap in a lot of cases. These Sports watches are water resistant to 100m and carry the simplified wave logo, again it can be found on their rubber straps. Now you know!

Seiko 7123-823B

With the back removed the two jewel calibre 7123 movement is revealed, it also had the wrong size battery fitted.

Seiko 7123-823B

A quick look at the dial and handset, the gold tones go nicely with the chocolate brown dial.

Seiko 7123-823B

A view of the day/date rings underneath the dial.

Seiko 7123-823B

With these removed you can see the keyless work and calendar components.

Seiko 7123-823B

With the movement turned over this is the motion work after the circuit and coil have been taken off.

Seiko 7123-823B

The wheel train and hacking/set lever exposed here.

Seiko 7123-823B

It was soon fully stripped ready for cleaning.

Seiko 7123-823B

Seiko 7123-823B

After cleaning and inspection it was time for reassembly, here the motion work is rebuilt.

Seiko 7123-823BThe circuit and coil are back on here.

Seiko 7123-823B

The calendar work going back together.

Seiko 7123-823B

Seiko 7123-823B

The calendar side coming together. The problem with the crown not screwing home was that the thread was worn on both the case and crown, a new crown was sourced, albeit one in gold not stainless steel but this has allowed it to now get purchase on the case threads.

Seiko 7123-823B

The seconds hand was loose on the pinion so that was tightened up and watch was placed on test for 24 hours. I noticed it was 25 minutes slow in the morning which was odd as it was bang on at 11pm in the evening. The time was corrected and when checked the next day there was a 45 minute loss. I had my suspicions that the canon pinion was too loose causing it to slip at date changeover time. With the watch stripped again I removed the offending component and re-inspected it. The canon pinion on a lot of quartz calibres aren’t the same as a canon pinion on a mechanical one, the way they are constructed is the wheel’s a separate component to the pinion and is crimped into a groove in the bottom of it. This allows it to slip when setting the time but holds firm when running. The canon pinion on this one had a crack in two places on the actual pinion which left the wheel a very loose fit, in fact when I prodded it with a piece of pegwood it fell to pieces!

Seiko 7123-823B

This was a nuisance as these pinions aren’t available any more so I had to find a donor movement to harvest one from. One was tracked down at the right price and eventually it was delivered to the workshop! You can see how the canon pinion should look in this shot.

Seiko 7123-823B

The watch was rebuilt with the replacement part and thankfully it survived the date changeover without any issues. I think the gold crown on this actually looks a better match for the watch with its gold accents on the dial and hands!

Seiko 7123-823B

Seiko 7123-823B

Seiko 7123-823B

 

 

4 comments

  1. An inspiring article, so inspiring in fact, that I decided to finally try to sort out an old 7123 Sports 100m that had similar problems. Yes, I ended up having to tear down two other 7123 movements to get a coil and canon pinion of the right height, and the date ring is not 100% (Like a lot of them out there!), but I saw the job through and now I’m happy. Thanks for sharing your work with the world.

    Like

      1. Sounds right, mine shows November of 1979 production. The 7123 doesn’t get a lot of love on the forums, but it’s been a good watch. Thanks!

        Like

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