Dating an accutron watch

Battery on the right, the 2 coils to drive the tuning fork on the top (with the ends of the tuning fork around the coils), and the mechanical part in the middle.The left coil actually consists of 2 coils, but we will get there later One huge difference to a conventional mechanical watch is that the power flow through the wheel train is inverted.Whereas in a traditional watch, the spring barrel provides the power and the balance keeps the watch from winding down quickly, it’s the tiny little wheel at the bottom (called the index wheel) that is driven by the tuning fork, which then drives the other wheels of the wheel train.

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But for this post, I will only take it apart and have a look at some details, and put it back together at a later time. The electronic circuit for the tuning fork is on the left - only a transistor, a capacitor and a resistor.

The capacitor and the resistor are there to provide an initial oscillator to start the tuning fork swinging when the watch is switched on.

I even found the original Accutron218 Service Manual on the internet – you can see a detailed description of the parts and their function in there.

One of the great inventions in watch making in my humble opinion, and a great piece of technology. Instead of a balance / hairspring oscillator, the Accutron uses a tuning fork that swings.

The electronic part is keeping the tuning fork swinging – all the rest is done mechanically.

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