Seiko 6138-0010 chronograph

This very early Seiko 6138-0010 “UFO” came in recently for some attention. The owner had bought it in 1971 when he was working as a race mechanic for the Tyrell formula one team when they were in Japan that season. He saw it on the wrist of a Japanese mechanic working for one of the other teams and fell in love with it so a deal was struck. It was worn continuously throughout his career and he eventually ended up running his own engineering firm that produced parts for race teams. The watch was regularly serviced until a number of years ago when he was told it wasn’t possible to get the parts anymore. He took it to a couple of watchmakers in the intervening years to try and get it resurrected but ultimately all that happened was it was returned not working with some parts missing! Having sold his company and taking life a little easier his thoughts came back to getting the watch repaired and this is where I come in.

The watch itself is a Japanese domestic market version of a model that has since been given the nickname “UFO”, the 0010 designation shows it was the Japanese “Speedtimer Sports” version. An early example like this is powered by the calibre 6138a, a hand windable automatic, 21 jewels, 21,600bph, twin register, column wheel with vertical clutch chronograph movement. The later models were powered by the calibre 6138b movement and there are a few subtle differences that I’ll point out later in the article.

Seiko 6138-0010

On the caseback the production date of June 1970 can be seen.

Seiko 6138-0010

With the caseback removed the movement can be seen….

Seiko 6138-0010

….and with the oscillating weight removed you can see the column wheel at the top of the shot with the autowind bridge below it and the balance bridge below that. Incidentally the pushers fitted are incorrect for this model, I wonder where the originals dissapeared to? It does make you wonder!

Seiko 6138-0010

Also the minute registers hand is incorrect, it should be a tapered black one.

Seiko 6138-0010

With the dial removed you can see the kanji day wheel, a feature of all Seiko JDM models. I’ve covered the strip down of these previously so I’ll just comment where needed 🙂

Seiko 6138-0010

Because it’s an early model the date driving wheel is metal not plastic, as is the intermediate date driving wheel. The date change finger is still plastic though.

Seiko 6138-0010

Seiko 6138-0010

Here you can see the hour register recording wheel driven directly from the barrel arbor.

Seiko 6138-0010

Seiko 6138-0010

With the movement turned over one of the differences between this and the 6139b is visible. The a movement has the intermediate minute driving wheel permanently fixed to the underside of the centre wheel bridge instead of being a separate wheel.

Seiko 6138-0010

And in this shot the reset hammer pivot isn’t eccentrically adjustable as they are on the b movements. The hammer return spring is also shaped differently on these earlier movements. One of the missing parts was the second coupling lever return spring.

Seiko 6138-0010

The third and fourth wheel top bearing and jewel aren’t covered over on the a, on the b there’s a cover which incorporates the intermediate minute recording wheels bottom bearing.

Seiko 6138-0010

Seiko 6138-0010

Soon it was stripped ready for cleaning and inspection.

Seiko 6138-0010

Seiko 6138-0010

Whilst the cleaning was taking place a set of correct pushers were substituted for the ones that were fitted, you can see they are longer and have decorative grooves machined in the end.

Seiko 6138-0010

The pusher o-rings are an important part to renew on these chronographs, it’s the usual entry point for moisture as the original o-rings are normally as hard as iron by the time they reach me.

Seiko 6138-0010

During inspection the hairspring was found to be roached, it’s more cost effective for the customer for me to swap it for a good assembly as opposed to reworking it.

Seiko 6138-0010

The missing second coupling lever spring was replaced.

Seiko 6138-0010

The intermediate upper crown wheel had also been lost so this was also replaced.

Seiko 6138-0010

Finally the centre wheels vertical clutch was useless, you can see part of the pressure spring poking out from the wheel on the left. As these aren’t serviceable it was replaced.

Seiko 6138-0010

The clean shiny bits assembled for rebuilding….

Seiko 6138-0010

….starting with the mainspring.

Seiko 6138-0010

At this stage the movement has to be turned over to get the bottom barrel arbor jewel in place.

Seiko 6138-0010

This means rebuilding the keyless work, the motion work and the hour recording wheels and levers.Seiko 6138-0010

Seiko 6138-0010

Once this plate is on it can be turned over and the chronograph levers and reset mechanism can be assembled.

Seiko 6138-0010

Seiko 6138-0010\Seiko 6138-0010

Seiko 6138-0010

The rough timing and beat adjustments are done at this stage.

Seiko 6138-0010

Seiko 6138-0010

Seiko 6138-0010

The complete handset was replaced (with genuine Seiko ones) as the old ones were tired and incorrect.

Seiko 6138-0010

The movement recased….

Seiko 6138-0010

….the autowind mechanism and oscillating weight refitted….

Seiko 6138-0010

….the caseback on and it’s done! A beatiful sympathetic restoration of a very early ( and very hard to find) JDM UFO. I love it and more importantly the owner was over the moon, he thought he’d never see it running again!

Seiko 6138-0010

Seiko 6138-0010

Seiko 6138-0010

Another nice touch was that it still had its original “Sports” bracelet, albeit a bit tight on the owners wrist now (funny how things shrink as we get older 🙂 ).

I didn’t have any original JDM links but a Pogue bracelet has very similar links so I tightened all the coupling links back up and installed one of those so the watch fitted his wrist comfortably again.

Seiko 6138-0010

Another bonus for me was the owner turned up to collect the watch driving his freshly restored 1967 powder blue Lotus Elan, believe me when I say it was absolutely gorgeous!

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