Seiko 6308A
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| Seiko 6308A |
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Description
The Seiko caliber 6308A, which debuted in 1976, was a very simple, but nevertheless
most rugged and reliably constructed selfwindig movement, which is able to run many
years without service.
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| movement view without rotor |
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This movement displays hour, minute, second and the current date. The date advances
semi-fast and can be corrected in the middle crown position.
The large four-leg balance regulates the pallet-lever movement with 21600 A/h. Of course,
it is secured in two Diashock protections to survice all kinds of shocks. The hairspring
is connected to a moveable hairspring stud and its effective length is set by the
hairspring key without long regulator arm.
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| simple but genious selfwinding mechanism |
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The selfwindig mechanism is - typical Seiko - genious and simple: An excenter changer
drives the mainspring by only one intermediate gear in both directions. This movement already
uses plastic parts in the selfwinding mechanism. This does not only reduce costs, but also
eliminates lubrication problems.
Seiko was so confident of the effectiveness of the selfwindig mechanism, that a handwinding
mechanism was left out. A little shaking is already sufficient to get it running.
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| movement view without selfwinding mechanism |
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The wheelwork is surprisingly simple, two ruby bearings are only found on the
escapement wheel; the directly driven center second and the third wheel use metal bearings
on the bridge side, while on the dial side, ruby bearings are used.
An interesting detail is the design of the more or less massive wheels: The minute wheel (second
wheel) uses two holes, the third wheel three and the fourth wheel (the directly driven center
second) contains four holes. This not only makes the gears lighter as faster they're turning
but also allow a simple identification.
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| almost empty main plate |
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On the dial side, most of the space is used by the elaborate date mechanism. At "11"
uses a driving wheel made of plastic and contains a moving driver which is responsible
for the semi-fast advancing of the date.
At "3:30" you see the quickset wheel, which is effective on the center position
of the crown and quickly advances the date by turning the crown. The opposite part of that
mechanism can be seen at "2".
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| dial side view |
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Another nice detail is the date spring at "7", which, unlike most of the springs on
other manufacturers, does not immideatly fly away when you work on the date mechanism.
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| dial side view without date mechanism |
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Technical data
| Manufacturer | Seiko |
| Caliber | 6308A |
| Number of jewels | 17 |
| Escapement | Anchor with pallets |
| Balance | Glucydur |
| Shock protection(s) | Diashock (Seiko) |
| Balance cock direction | clockwise |
| Hairspring stud | moveable |
| Regulator type | Hairspring key |
| Movement construction | Fork
Escapement wheel, Fourth wheel, Third wheel
Center wheel
Mainspring barrel |
| Features | SCD,QG,RDR,AUT |
| Functions | Hour, minute, second, day, selfwinding |
| Beats per hour | 21600 |
| Size | 12''' |
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| Factsheet |
Usage gallery
