WS 19: Servicing a SEIKO Chronograph 6138
This picture shows the heart of the chronograph mechanism of
the 6138. The wheel in the center is the chronograph wheel - vertical clutch
assembly. The chronograph wheel is partly covered by a large wheel on the right.
But in the very center of the movement, you see a golden part connected to the
chronograph wheel with a little finger connecting to a wheel left of the center.
What wheel connects to the golden wheel at 9:30. This is the mechanism that
drives the chronograph minutes. The chronograph minute subdial is at 12 o'clock
when looking at the dial or from this view, below the golden wheel on the left
with the two openings.
You can also notice 4 levers interacting around the column wheel. The biggest visible wheel just above the main barrel on the right has been identified as a "wrong wheel" by Rob almost instantly. He verified his observation with another 6138 movement in his stock and quickly found a matching wheel. That wheel with the beveled center is from a SEIKO automatic movement.
Later I will show a similar picture with the cleaned parts, I just want to raise your attention to the two complicated springs. Having a picture to refer to when reassembling is certainly a good idea. Springs are always a bit of a pain. First they fly off the movement easily and second, the placement of the springs is more complicated then that of any other parts. At the bottom of the picture, the dirtiest part of this movement: the balance assembly.
Please click on the picture to read on >>>