Not only Bulova built tuning fork watches. The Swiss movement manufacturer ESA also made a tuning fork movement under licence from Bulova. Amongst others, Omega used this movement in their Omega Electronic Geneve Chronometers.
Kim sent this one over for a service, so let’s see what lurks inside…
A first look clearly shows the two coils that keep the tuning fork humming.
The bottom plate is fairly standard.
The bridge has the tuning fork attached to it, and the index and pawl fingers, and of course the index wheel that is driven by the index finger. Overall, I prefer the ESA construction over the Bulova one, as it’s easier to work on, and the pawl finger position is easier to adjust.
With the little bridge removed, you can now clearly see the index wheel (the smaller of the two wheels in the centre).
The top plate is an easy enough construction, with the second hand arbor having a spring pressing against a plastic ring to make the movement of the hand smoother and to prevent vibration.
With the little bridge removed, you can see the plastic ring, and the wheel above that contains the clutch so that you can set the time without turning the index wheel.
Now it’s time for the bottom plate.
The electronics are kept away from the cleaning machine.
Reassembly starts with the top plate.
Now the index wheel and bridge are mounted.
Then the coils and circuit go in.
Now the tuning fork bridge is mounted on the top plate, and, after putting the battery in, I can adjust the index and pawl finger position.
Finally, I put the bottom plate back together.
With the dial and hands back on, I case the movement, and the watch is humming happily again.