I received this Seiko 6138-3002 from a customer who lives fairly close to me in Somerset, UK and it’s not run for some time… These are a great technical accomplishment by Seiko and this movement calibre was released in 1969 – there is a little history here.  It’s a big watch being part of the jumbo collection and on a par with watch sizes today.  Its somewhat marked but you can see a good condition dial under the scratched crystal.

Seiko 6138-3002 - overall before

My customer receives a 65 page document showing the review, cleaning, checks, build and performance of his watch but, kindly allowed me to post some pictures here.

Stripped and cleaned. There are a lot of parts in this calibre – these are the base movement parts.  Because of the vertical clutch design, some of the chronograph parts also form part of the base movement.

Seiko 6138-3002 - base movement parts

And these are the remainder of the chronograph system, calendar and automatic system parts.

Seiko 6138-3002 - chrono auto and calendar parts

I’d already found the major fault (broken mainspring) and the whole movement was gummed up with old oil and grease. This is the centre chronograph wheel which incorporates a vertical clutch that controls the parts of this wheel that turn – some parts run all the time as the fourth wheel in the train and when the chronograph is started the central pinion turns as well because that’s where the chronograph second hand is mounted. These fail and are extremely hard/expensive to source but, fortunately, this one checked out.

Seiko 6138-3002 - centre chrono wheel

All the parts are checked under the microscope for cleanliness and wear – this example is the second wheel and the pivots look very good, as does the whole wheel.

Seiko 6138-3002 - second wheel pivots

The keyless works are installed on the dial side and then the movement turned over so that the barrel, second wheel (hidden), 3rd, 4th and escape wheels may be fitted.

Seiko 6138-3002 - build train

The layers are built up until the base movement, which includes part of the chronograph, is complete – here just waiting for the balance and the watch will run.

Seiko 6138-3002 - build base complete

There are some adjustments made at this stage to ensure the best performance and after a few days running to confirm power reserve and accuracy, the dial side moves forward.  This shows the remainder of the keyless works that control the quickset day and date plus, at the upper, the hour recorder/brake/hammer.  That spring eccentric needs an adjustment here as it should line up with the hour recorder pivot and, as received, it has chrono creep when I test that before fitting the calendar.

Seiko 6138-3002 - build hour recorder

And then the calendar plate, day/date rings and mechanism are added. This side is complete and ready for the dial and hands.

Seiko 6138-3002 - build calendar complete

With dial and hands fitted, there is some work to do on the case.  These are the parts that make up the case before cleaning.

Seiko 6138-3002 - case parts dirty

And post cleaning – all looking very nice.  A new crystal was fitted along with new case, crown and pusher seals to bring back the case sealing.  The water resistance was checked when assembled and it passes which will be good for longevity.

The movement is re-fitted to the case and the auto mechanism added.  All that’s left is to replace the case back and fit a bracelet before the watch goes into two weeks of testing to confirm all is well.

Bracelet fitted and this is a stunning watch with great presence on the wrist.  Now running with only 15 seconds/day variation over the six test positions at full wind, and consistently showing +5 seconds/day on the auto tester which simulates use on the wrist.

Seiko 6138-3002 - build finished

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