What could cause a watch to freeze up until the chronograph is started?

[DoctoralHermit]

I recently posted that my Sugess ST19 moonphase chronograph locked up, and would not start again even when shaken, or when I opened it up and spun the balance wheel a little bit (click here for the post).

Today, I tried for the first time clicking the chronograph start button. Suddenly, the watch itself started running again (even the non-chronograph timekeeping!). Now I'm curious, though, what the problem with my watch is. Any ideas what it could be?

[HSL]

Are you sure it stops when the chronograph doesn't run, it is usually the other way around since you apply more drag to the drive train with the chronograph part.
The usuall fix is to adjust an excentric screw wich regulates the distance to the drive wheel in the center.

The chonograph engaged..

Edited April 15, 2020 by HSL

[nickelsilver]

This has a Venus 175 copy if I'm not mistaken. It's possible the coupling clutch depthing to the driving wheel is too tight, but when you engage the chrono it's just enough movement that it lets it run. That'd be the first thing I'd check. Then recheck the depthing coupling clutch to chrono runner. The clutch-driving wheel should be about 2/3 deep, clutch to runner about 1/3 deep.

[DoctoralHermit]

Thank you for the replies! I'm certain that the watch is not supposed to stop or anything when the chronograph is running... its a very strange problem.

Its the same movement as the SeaGull M199s... I believe it's called an ST1908, although that also refers to some movements without the moonphase function.

Thank you for these suggestions! These will give me a good place to start if it ever happens again, at which point I'll be sure to update watchrepairtalk!

[Squeme]

Does it work since more than 2 years now, or the problem come again randomly / permanently ?

(just to understand if this is a common problem or not ...)