Many of the Seiko dive watches from the 1960’s and 70’s have rightly gone down as design classics, building a considerable following amongst watch collectors. Conversely some truly gorgeous watches from the same period produced by the same company have quietly slipped below the radar for the simple reason that they were designed for the typically much slighter of wrist, lady diver (or indeed, the lady desk diver). I’ve written about two such examples before but in today’s post I would like to revisit one of those watches – the lovely 2205-0760 – a 150 m rated dive watch featuring a high beat automatic movement with date quickset and hand winding. The watch in question is that featured in the earlier post but since we last left it, it has been resting, rather neglected in a drawer having ground to a halt a few months after a service by a professional watchmaker.
At the time, I did not especially relish the prospect of servicing it myself and so instead bought a 21 jewel 2205 ladies dress watch, the idea being simply to swap the movements over. Having done so, needless to say, the replacement movement also faltered and so the watch retired temporarily, waiting its turn at the top of the queue. Somewhat to my shame, I find myself embarking on its revival a full 4 years later, but now that I’ve resolved to do so, let’s proceed without further delay.
Our starting point is the watch case fitted with that 21 jewel replacement 2205A, with the original 17 jewel movement sitting forlornly to one side:
The watch case bezel measures about 32 mm across and so you can perhaps get a good idea of just how tiny the movement is. You will see that the dress watch variants sport rather snazzy red on white numerals on the date dial where the divers movement uses white on a black background. The size of the movement presented me with the biggest single challenge in completing the service, not least of which was the extreme difficulty in securing it into a movement holder. This problem derived in part from the hugely inappropriate size of the holders I have to hand but also from the fact that the landscape either side of the main plate make it very difficult to find an orientation that keeps it level and secure. You should appreciate the extent of the problem from the photo below of the movement sans rotor looking suitable ludicrous in the relatively giant movement holder:
A closer look reveals a surprising degree of tarnishing in a movement which had comparatively recently undergone a service but perhaps that is testament to the fact it has been sitting in a watch parts box for the past 4 years.
This complexity derives to a large extent from the fact that the watch hand winds but even so it is nice to see so much intricate engineering in such a tiny movement. It also makes a pleasant change to see a design that does not rely on the ubiquitous magic lever system used in so many other Seiko automatic movements.
In this design, the rotational motion of the winding weight transfers torque via one or other of the idle wheels on the rocking seat (depending on the direction of rotation) to the first reduction wheel (still attached to the ball bearing above) which meshes with the second reduction wheel which then acts to wind the mainspring via the ratchet wheel on top of the barrel. You may get a better idea of how this works from the schematic from the 2205A service manual shown below:
The role of the first reduction wheel click (which we’ll meet later on) is to prevent reverse direction rotation of the first reduction wheel and the resulting unwinding of the mainspring. If we remove the second reduction wheel, we get sight of the intermediate pinion for the ratchet wheel which plays the role of a clutch to permit hand winding without sending the autowinding rotor into a spin.
When hand winding, the intermediate pinion ‘clutch’ slips thereby not transmitting rotation to the second and first reduction wheels (see Fig 4 below) but the same part will mesh with the second wheel when the rotational motion derives from rotation of the auto rotor, transferring power to the main spring (Fig 3 below).
The multiplicity of stacked bits and pieces clustered north east of the keyless works parts facilitate the operation of the date quickset which is achieved by pulling the crown outwards from the time setting position. This mechanism is not unlike that used in the Omega 565 movements used in Seamaster watches from the 1960’s but in this application is spring loaded. We’ll take another look at this when it all comes back together after cleaning. Stripping the rest of the calendar parts away we can take a quick look of the naked main plate before turning over to continue on the balance side:
The train wheels in this movement adopt a classic layout (if not a classic Seiko layout) with the fourth wheel and sweep seconds pinion separated, the latter driven by the third wheel and the fourth wheel hidden beneath the centre wheel bridge:
The jewelled bearing in the centre wheel bridge turned out to have been damaged at some point in its past (something I would have hoped the previous watchmaker might have attended to) and so the bridge from the 21 jewel dress donor will serve as a replacement when we come to rebuild the movement:
A good clean and rinse in the ultrasonic bath later, the entropy minimization process begins, first with the winding pinion, clutch, yoke, setting lever and setting lever spring, seated with a temporary stem taken from the 2205 dress watch donor:
At this point, we flip back over to put the balance side together, starting with the centre wheel, escape wheel, and fourth wheel, secured into place by the centre wheel bridge, then the barrel plus ratchet wheel, third wheel, sweep seconds pinion and barrel and train wheel bridge:
A bit of power into the mainspring confirms the watch runs happily at its rather manic 28800 beats per hour. Next, we turn back to the calendar side, fitting the setting wheel, minute wheel, minute wheel bridge and cannon pinion:
The quickset works by pulling the crown outwards, with the stem causing the setting lever to pivot outwards, acting upon the date corrector which moves the date corrector lever against one of the teeth on the inner side of the date ring. The date corrector spring causes the stem to return to the first click position automatically after each date quickset operation.
I’ve opted to use the rocking seat from the 21 jewel movement because it uses fixed idle wheels rather than then seemingly slacker arrangement of separate idle wheels seated on individuals pinions. We fit the automatic ball-bearing next