The SBDC007 is a great divers watch by Seiko. It is extremely light thanks to its titanium case and bracelet. This particular one had already received a sapphire crystal upgrade, making it a very handsome watch indeed.
This model, also nicknamed the “shogun” by collectors, is the first version of this watch, not to be mistaken with the later SBDC029. Although both models are very similar in appearance, there are subtle differences in the design of the dial.
The watch is powered by the very reliable Seiko 6R15 caliber. a higher-spec derivative of the familiar Seiko 7S26. The 6R15 features a hacking function and a hand winding mechanism. It also has a longer power reserve. This watch has a date function only, although the movement is designed to accommodate both day and date complications.
This particular watch had a very low amplitude given its age – the picture below shows a value of 165deg when fully wound. Although Seikos have a reputation for low amplitude, I would have expected this one to be in the region of at least 260deg, ideally more. The rate curve is also very irregular, and the beat error very high so it is definitely time for a service.
We start by opening the case. The friction between the titanium case and case back feels slightly different to stainless steel watches. This is probably explained by the fact that titanium on titanium has a higher coefficient of friction than steel on steel.
Upon opening the watch, we have a full view of the 6R15 movement. No fancy decoration here, although the oscillating weight has a nicer finish to that of the 7S26 movements.
The movement is taken out of the case, and the hands are carefully removed.
With the oscillating weight removed, we can now clearly observe the similarities with the 7S26 layout. The main difference visible here is the presence of the automatic train bridge.
With the automatic train bridge and the second reduction wheel and pinion removed, you can see the manual hand winding system of the 6R15 movement.
The stripdown continues…
But I am only able to take it so far as the cannon pinion is still present on the dial side.
So we move on to the dial side.
Now we can remove the cannon pinion. It is mounted on the arbour of the centre wheel.
With all parts stripped down, I also open the mainspring barrel. The barrel and arbour will be ultrasonically cleaned with the rest of the parts, whilst the spring is cleaned manually.
The watch fully stripped down.
Work begins with the lubrication and re-build of the the barrel, arbour and mainspring assembly.
I then manually clean the balance wheel end stones before oiling them.
Keyless work and centre wheel and bridge are now in place.
Mainspring barrel and escape wheel installed.
Third wheel and fourth wheel in place. Click spring also added.
With the barrel and train wheel bridge and the automatic train bridge back in place, this nearly concludes the assembly work on this side of the movement, just leaving the oscillating weight to be fitted later.
At this stage, a quick check on the timing machine indicates that the watch is running as expected with a good amplitude and a very regular beat rate, so after a coarse adjustment and regulation I proceed with the rest of the assembly. The 6R15 movement is fitted with the Etachron system which makes any hairspring adjustment much more straightforward.
Here you can see part of the date and time setting mechanism.
The motion work, calendar work, date jumper spring and day disc are now back in place.
This just leaves the fitting of day disc guard. No day date corrector wheel and day star on this movement, it is a date only!
With the hands back in place, the movement is now ready to be re-cased.
Once re-cased, I let the watch run for some time before I do the final beat adjustment and adjustment of the rate.
And finally, as this is a divers watch, I also carried out a pressure test.
Doesn’t this watch look fantastic?