This Electronic Seiko from October 1969 came in for some tender loving care recently. Electronic watches had been around for quite a while by the time Seiko released their first Electronic watch, Hamilton, LIP and Bulova were a few of the other major manufacturers from that period. However, Citizen’s X-8 Cosmotron of 1966 is generally accepted as the first commercially successful electronic movement that was regulated by a balance wheel. Seiko responded with the calibre 31xx in 1967 followed by the calibre 37xx in 1969, the 32xx and 33xx in 1972, and the calibre 07 Elnix series in 1973/4. Japanese electronic watch production was short lived due to the rapid development and falling costs of quartz production of which Seiko was first to market with in 1969 with the calibre 35 Astron. The 3102-7000 “Electronic” featured here came in with problems to the running and quick setting of the movement, you can see in the opening photograph the minute and hour hand are out of sync.
The caseback has a lovely atomic stylised logo which is also present on the dial. Forged in the white heat of sixties technology!
With the caseback removed you can see the mixture of old and new technology with the electronic circuits and coils and the traditional balance wheel regulation. The movement actually looks in pretty good shape with none of the electrolyte deposits so often found in elderly battery driven watches.
The first thing I removed was the balance assembly, this is pretty much the same design as you’d find in any mechanical watch.
I then uncased the movement and removed the handset and dial.
Underneath you can see the calendar top plate and date wheel.
Once I’d removed the top plate you can see the date corrector and date jumper and spring.
This was soon removed to reveal the motion and keyless work, you can also see the underside of the coils and circuitry.
The date wheel and date corrector lever and spring were removed next.
Once I’d stripped the keyless and motion work the culprit for the out of sync hands and the quickset problems was revealed.
Degraded lubrication resulted in increased torque when quicksetting the time, this had got so stiff and dry that the minute wheel’s pinion leaves couldn’t cope and had separated from the wheel itself.
As parts for these are virtually impossible to source (my parts catalogues don’t even list the calibre) I elected to stake the wheel back onto its pinion leaves.
The movement was then turned over and I removed the circuit plate.
The wheel train was next to be stripped.
On inspection I found the centre wheel had the same problem as the minute wheel, namely the wheel had come loose from its pinion. As with the minute wheel I also staked this one back together.
The movement was fully stripped now and ready for cleaning.
It’s worth adding a brief description of how this movement actually operates, In a traditional movement the escape wheel delivers an impulse to each of the pallets in turn which translates to the other end of the fork giving the balance wheel impulse jewel a kick providing the impetus for the balance wheel to oscillate. In the later Seiko Elnix (calibre 07xx) type of movement the balance is given the impulse via a coil that sits between two magnets attached to the balance itself. However in this earlier type the pallet fork itself is given an impulse electrically, much like the stator in a quartz watch. Unlike a stator the pallet fork doesn’t rotate in one direction, the impulse is alternated between the coils so it moves in one direction for one pulse and the other direction for the next. You can see the permanent magnet “stator” element underneath the actual pallet fork in the next photograph.
The oscillation of the pallet fork in turn drives the escape wheel, unlike a normal watch where the escape wheel is the component that drives the pallet fork. At the horned end of the pallet fork the regulation of the movement is governed by the traditional balance wheel and can be regulated in the usual way. A benefit of this system is the increased isochronism of the movement as there’s no fluctuation in the power delivered by a mainspring as it doesn’t rely on one! These movements are surprisingly stable and accurate when running but of course there will still be fluctuations due to position and temperature. You can see the different tooth design of the escape wheel below, there’s also a ratchet wheel positioned above the escape to prevent it moving backwards whilst being worn as that would result in the movement locking up.
Once the parts were out of the cleaner I began reassembly. As always I rebuild the balance assembly on its own so that I can check for enshake, trueness and hairspring geometry whilst it’s still relatively easy to see from each direction.
Once I’m happy with the balance I remove it again and I then start assembling the train, lubricating as I go.
The bridges are fitted here and it’s ready for the circuits to be replaced.
The circuit plate is back in place in this shot….
…and the balance is refitted here.
Turning the movement over I can start on the under dial components, I’ve refitted the keyless work here.
The motion work and quickset components are done here.
The calendar bottom plate and date disk are the next components I fit….
… then the top plate goes back on.
The dial and hands are next….
….then the movement is recased and I fit the battery and strap. Note how the battery is positioned positive side down as opposed to the more usual negative side.
Once I’ve refitted the caseback the job is done and she’s ticking away sweetly once more. It’s lovely to see unusual watches such as these on the bench from time to time 🙂