In this chapter we will continue with the disassembly of the remaining units, starting with components in the power source unit, then the oscillator and then we will disassemble the counter or train wheels. In addition, the last step is to pull apart remaining components in the time and calendar setting assembly.

There are a couple of potential 'booby traps' so please read the entire chapter before proceeding with disassembly.

We have also reached the stage where we will have to remove bridges or plates which hold the components in place. It is important to understand that once screws are removed, the bridge is still secured in place because it's held by alignment pins. Therefore most bridges must be 'lifted' from the main plate 2-3mm before being removed. Placing a screwdriver at that exact point is necessary in order to avoid any potential damage to the components underneath the bridge.

Another important thing is to hold the components with tweezers at a certain point (for example it is fine to hold the large pinion directly with tweezers, but that would be inappropriate for smaller ones). If in doubt, refer to photo.

The most sensitive of all components is the hair spring which is attached at one end to the balance cock and another end to the balance wheel.

And here are couple of examples of inappropriate handling:

The balance wheel assembly should be placed / rest in 'cock down' position, not the other way around!

Another way of mishandling is to remove the assembly without paying attention to the components which may be obstructing the hair spring or the balance wheel. In other words, the hair spring or the balance wheel could be partially "tucked" under by a nearby component like a bridge or wheel.

In the case of Seiko 7S26, the hair spring itself is not obstructed, however the balance wheel is! It is sits partially under the 4th wheel and train bridge.

Pulling the cock directly vertically during assembly will result in deformation of the hair spring - you will be pulling the cock up, but the balance wheel will be obstructed so the spring will stretch beyond the point of elasticity. Again, pay attention to the images below and you'll be fine.

We will talk about the balance wheel assembly in more detail later on.

Turning the power "off"

Before we can proceed further with disassembly, we need to unwind or uncoil the main spring. Now, if you have commenced disassembly more than 2 days ago, your watch has stopped and the spring is already unwound. However it is important to do the following steps regardless.

As we already know, the auto winding unit winds the spring by turning the ratchet wheel clockwise. We can wind the clock 'manually' too, by turning the ratchet wheel screw clockwise. It takes 8 rotations ( 8 x 360 degrees) to wind the spring fully. However we will wind it just two turns, to get the feeling of winding action and spring tension. So turn the ratchet wheel CW, two full rotation.

The unwinding of the main spring is a three-step process.

1. Turn the ratchet wheel for a few degrees (few clicks) and hold the tension
2. Unlock the ratchet spring by pushing it gently towards yourself until it disengages from the ratchet wheel and HOLD it disengaged with tweezers.



3. The spring is now trying to overcome your holding pressure by turning the screwdriver anti-clockwise. Slowly release the grip on the screwdriver body and let the spring unwind. Attention: Do not let the screwdriver turn instantly - instead control the unwinding action with the "right amount of grip."