Watch suddenly gains minutes a day

[SmallestGiant]

Hello everyone,

 

Some time ago I bought a watchmaking kit for an automatic chronograph using a Seagull ST2901. When I first started using it after completing the assembly I noticed the watch was working with a comfortable deviation of less than +/-10 seconds a day though after 2 to 3 days of normal usage (wearing it 8 to 10 hours per day), it would suddenly start gaining time, up to 10 minutes a day. The following morning, having left it alone for 8 to 10 hours it would once again exhibit a rate of +/-10 seconds a day. I have repeated the same experience several times with the same results.

The following pictures are the rates measured with the watchcheck app as well as two readings from the watch accuracy meter app with the watch fully wound.

 

The watch has not been submitted to a professional watch repairer.

 

Thank you

[Kalanag]

There is an issue with the balance spring most likely.

When segments of the coil stick to each other or to the balance cock the rate starts speeding up. Make sure the hair spring is not bent (should be spaced evenly), 100% clean and not magnetized.

Edited March 7, 2024 by Kalanag

[Neverenoughwatches]

14 hours ago, SmallestGiant said:

Hello everyone,

 

Some time ago I bought a watchmaking kit for an automatic chronograph using a Seagull ST2901. When I first started using it after completing the assembly I noticed the watch was working with a comfortable deviation of less than +/-10 seconds a day though after 2 to 3 days of normal usage (wearing it 8 to 10 hours per day), it would suddenly start gaining time, up to 10 minutes a day. The following morning, having left it alone for 8 to 10 hours it would once again exhibit a rate of +/-10 seconds a day. I have repeated the same experience several times with the same results.

The following pictures are the rates measured with the watchcheck app as well as two readings from the watch accuracy meter app with the watch fully wound.

 

The watch has not been submitted to a professional watch repairer.

 

Thank you

As mentioned by kalanag when the hairspring coils touch each other or anything else then the timing rate position on the coils is moved to a faster oscillation.  This might be sticky coils from oil contamination or maybe magnetism of the hairspring. It isn't always a consistent condition as the coils may stick together then periodically free themselves.  Also noted the amplitude of your two  readings, one is very low the other is very high.

[Malocchio]

Demagnetizing might free a sticking hairspring coil even if it's not magnetized. I have this Seiko 6309 that used to be very accurate but suddenly started gaining +70 s/d. A compass didn't show any signs of magnetism but I demagnetized anyway and it returned to a flat 0 s/d. I didn't open the caseback so I don't really know what the issue was.

[SmallestGiant]

Thank you all for your advice.

I will try to demagnetize it first and if it doesn't fix it, I will try to find a watch repairer willing to do a cleaning job on a chinese movement.

[nevenbekriev]

Actually checking with compass is not so reliable. It is possible that several magnetized parts neutralize each other's filelds and compass shows no magnetization. This is the reason for the fact that demagnetization of whole movement is not so effective as demagnetization of dissassembled parts of the movement separately, in which case much lower strenght of alternating magnetic field is enough.