Calling all watchmakers ( @Archer ), My minty Seamaster has been running almost perfectly until today. Perhaps it was a sudden jolt (not sure) but it is now running +70 sec a day with a defined galloping sound. What could be the cause and how serious an issue is this? Mainspring or hairspring issues? Is it strange that an event would cause this? Thanks. Patrick
Egad! Thanks @Kringkily i will look into that. I have that Lepsi app on my iPhone - better check. I thought it would be something more nefarious!
I think it could be many things and that one cannot tell without looking at the movement. But when a watch is magnetized, it usually run much more faster.
Rebanking is caused when the balance amplitude is so high that the roller jewel (impulse pin) strikes the outside of the pallet fork horn. This causes the balance to bounce back the other direction faster than the balance spring would normally return it. It then bounces off the other side of the pallet fork, and continues to cycle back and forth quickly. This is normally something that doesn't show up spontaneously since it's often due to an incorrect (too strong) mainspring being installed in the watch, or too much braking grease on the barrel wall of an automatic, or problems in the escapement. However, if the beat error is out by a very large amount (possibly from a shock that has distorted the balance spring) then the watch could be running a much higher amplitude in one direction of the balance than the other. If the amplitude was already quite high to begin with, this could be enough to tip it over the edge into rebanking. One way to know for sure it is actually rebanking is to hold the watch horizontal (dial up or down) wait for the rebanking sound, and then turn the watch to a vertical position - the amplitude will drop and the rebanking should stop. You could try demagnetizing the watch also - difficult to say if it's due to being magnetized or not. Maybe you knocked it against a strong magnet and now it has both problems.
Thank you so much @Archer . I am waiting for the watch to wind down so I can have a look at the hairspring to see if there is obvious distortion. I can discern a difference in sound from a horizontal vs. vertical position slightly. Thanks for the detailed explanation - I will bring it in for a checkup and service soon anyway. Best regards, Patrick
If the bridle gripping is the problem, the knocking might disappear after about 1/2 hour with the watch in a static position. If the bridle is okay but the spring too strong, it will likely take hours for the knocking to diminish, if the watch left in a static position. You say it had run okay, without knocking, for a time. I am inclined to think the bridle is gripping. I don't recall ever seeing over rotation of a balance wheel as a result of magnetism.