Landeron 248 seconds hands stuck

[yianwee]

Hello all.

I've just recently acquired a vintage watch with a Landeron 248 movement. The watch runs fine, keeps reasonable time and the chronograph works well when it is placed lying flat on a surface. However, when it is worn or lying flat turned over (e.g. crystal is touching the table surface), the watch gets suck at the 40 second mark. When I turn the watch back face up, it continues running again. I've attached some pictures below.

I am quite new to this, so could anyone share any insights as to what could be the issue?

 

[RyMoeller]

Looks like there is some debris in the movement and that may cause issues.  From previous experience here's what I'd look for:

1. Debris that may get in the cogs of the gears.  A watch that hasn't been serviced in a bit will have lower amplitude and that will make it easier to stop when dirt and debris gets in the way of the gears meshing.
2. The second hand may be colliding on the dial side with something- this can stop the watch cold as well.  Usually this results from hands contacting each other but if there is debris under the dial and/or an aggressively bent second hand then it may be colliding with debris, the inside of the crystal, or the dial itself.
3. Damaged teeth- check the fourth wheel, driving wheel, and chronograph runner specifically.
4. Bent pivots- check the fourth wheel, chronograph runner, escape wheel, and balance.
5. Jewels and Pivots- If the watch runs fine dial up but poorly dial down then perhaps there is a pivot that is too short (or a the jewel is gummed up) and the problem only presents itself when gravity is pulling the pivot into the jewel.