WS 22: Servicing a SEIKO 7005 including replacing the balance
The picture below shows the new mainspring that did not make it into the movement. Here is why and what had happened. The movement did not run smoothly with the new balance wheel. So this might not have been the sole reason for its erratic running. I decided to sleep over it and think... and then remembered the dirty barrel and mainspring. I had a spare mainspring that fits the 7005, 7009, 7S26 and 7S36 barrels.
On the next day I also used a big screwdriver to wind my spare 7009 movement which is very similar. Winding with a screwdriver is necessary because these movements do not have a manual winding system. I noticed a much higher torque in my new spare 7009 movement. This convinced me to prepare even more courage and to open the barrel again and remove the main spring.
The second disassembly went fairly quickly. Removed the rotor. Removed the
balance cock with the new balance wheel and then I removed the whole automatic
winding system in one. I opened the barrel again and slightly pushed on the
barrel arbor and "whizz" out sprang the old mainspring.
I knew that I had to be extra careful, I had seen somebody replacing a new mainspring and then ending up "winding it manually" back into the barrel. Note the aluminum ring below, replacement mainsprings come wound in those aluminum rings. Ideally the ring (blue on one side, metallic on the other) is placed over the open barrel and then the new mainspring is pushed into the barrel. I managed to get the spring into the barrel except for the stiff end (red on my little note) that creates the friction between the barrel wall and the spring. There was no way I could work that new mainspring into the barrel, so I let it go. "Whizzzzz!" number two and the new mainspring landed safely... and of course unwound! Hm!
Now what to do? I decided to practice "handwinding and contracting" the old main spring back into the barrel. I started at the inner end first and tried to wind the spring so it contracted and could be pressed into the barrel again. Now that is hard on the thumbs and indices... after two tries I had to take a break. The finger tips really get a beating!
Then I had a good idea. I started at the outer end where the spring has two layers. I have marked that red in my little note. The hardest is to get that double end nicely into the barrel. Again the finger tips started to complain. But magically enough, I was able to get the old spring back into the barrel. At this time my finger tips hurt so much, I was simply not ready to take it back out again and do the same procedure with the new mainspring. I tested the torque of the mainspring and surprise! Now the torque of the barrel was amazing! When playing with the movement before the removal at the mainspring I had noticed that when I pushed on the wheel of the barrel increasing its torque, it started to run immediately. So now I was very happy that my "handwound" old mainspring obviously delivered enough torque to keep the watch running. And it is running nicely now and I am happy to have solved these problems.
Note that there are mainspring winding tools. The Swiss made version is quite expensive and this was the reason I had not bought one. Now with this rather painful experience, I am more inclined to look at them once more ;-)
Now that the watch was running fine with the old mainspring and with my hurting finger tips, I decided to store the unwound new mainspring away, adding a note how to wind it into the barrel. I was not able to attempt a fourth "handwinding" attempt with the power left in my fingers.
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