I have just bought a watch with cal 30 movement, the movement is running very fast around 1 hour 30 mins over night. The brequet hairspring is not touching, I have also demagnetised the movement but it is still running as fast. I am not sure if the balance has been replaced. Is the cal 30 balance different from a 30t2 balance? Any ideas would be much appreciated. Thanks Mick
Mick, it sounds like you have already checked the two most obvious things to cause fast-running - a hairspring with sticky coils or a magnetised movement. Gaining 90 mins a day is pretty good going, and points to something major being the cause IMHO.
I would not jump to conclusions about the mainspring just yet....this could be the result of several things - are you sure for instance that the overcoil is between the 2 regulating pins? If it is, are the pins pinching the overcoil, or is the spring bouncing back and forth between the pins? Where is the regulator positioned? Does it look like balance screws are missing from the balance? Has the movement been serviced? If it is the wrong mainspring, you don't need to swap it to tell. If the watch is knocking due to balance amplitude that is too high, you can hear it. Here is a video I took a while back using a cheap manual wind movement - it is fully wound and when I apply extra pressure to the crown (as if I'm winding it) you can hear the escapement sound change - it sounds like a horse galloping a little bit. If you don't hear this at full wind, then it's not a mainspring issue. Cheers, Al
Thanks Al. The overcoil is inbetween the pins, it is not pinched, on close inspection it moves between them a tiny bit. The screws are all present without any missing. No galloping sound either as in your video hen you apply pressure to the crown. The regulator is in the middle. I have just time it via my phone and it gains 25 seconds in two minutes. Thanks Mick
I'm going to guess that since you didn't answer if it was serviced, it has not been, so that is step #1. Cheers, Al