Advice on pocket rattrapante w/ instantaneous minute counter

Hello master watchmakers,

I have recently purchased a monopusher split-seconds chronograph with capped column wheels (2x) and instantaneous minute counter (photo of the movement attached).



Unfortunately, the split seconds function seems to be malfunctioning.

1. When the chronograph is engaged, the split second hand initially moves in sync with the main chronograph hand.

2. However, after 30 seconds or so, the split seconds hand would stop by itself, without me pressing the split seconds pusher.

3. Then after another 30 seconds or so, the split second hand would creep back and eventually catch up to the main chronograph hand, again without me pressing any pusher.

From the description of the problem, would you be able to tell if it's an issue with worn parts or that it simply needs to be cleaned and oiled?

If the latter, how much money should I budget for repair?

Thanks so much!

Peter

I am not a watchmaker but I am interested in the rattrapante/split-seconds complication.

For the split-seconds hand to stop while the chronograph is running, the split-seconds wheel must be stopped as well. When the movement is functioning properly, the split-seconds clamp performs this task. For the split-seconds hand to move with the chronograph seconds hand, the split-seconds lever must be pressed against the split-seconds cam by a spring.

I would imagine that a worn spring, coupled with improper lubrication, could cause the symptoms that you are describing. If the existing spring cannot be salvaged, a replacement will have to be found or fabricated.

Irrespective of my unqualified diagnosis, it is a stunning movement deserving of a service.

@DirtyDozen12 thank you! That was super informative. Thanks for taking the time to explain

No problem. Here are a couple of visual aids for those interested. The components in @pcdubc's watch are of a much higher quality but this Habring2 module is nicely exposed.

The split-seconds (ss) cam rotates with the chronograph seconds hand whereas the ss wheel (and therefore ss lever) rotates with the ss hand. The ss lever is pressing against the ss cam at all times. When it is not held by the ss clamp, the ss wheel 'synchronizes' with the ss cam as a result of the interaction between the ss lever and the ss cam. The ss cam is shaped in such a way that the position of the ss wheel will only be 'resolved' when the ss lever comes in contact with the flat end of the ss cam.


Fantastic images courtesy of http://www.watchesbysjx.com/2013/04/up-close-habring2-doppel-3-rattrapante.html

@DirtyDozen12 thanks so much again. I leaned so much from those photos