I recently picked up a 321 Seamaster (145.006). On pushing the top chrono pusher (usually to stop), the stop seconds hand often "jumps" 2-3 seconds backward.

Any thoughts on what could cause this? Magnetism? Any other ideas? Anything major?

Anyone cure this same issue?\

Thanks
Mike

 

Can you take a video of it?

 

Thanks for taking a look.

 

Could be a worn hammer spring? Part 3201734.

 

Thanks... Seems like those are not so easy to find these days.

Mike

 

I'm probably wrong. Wait for the watchmakers to check in. Or go visit yours. Good luck.

 

I'm no watchmaker but it might be your brake. When you activate the chronograph the castle wheel is engaged and the coupling clutch with drop in and engages the sweeping center second wheel, the hammer gets pulled back and the intermediate counter wheel drops into place. when you stop the chronograph the coupling clutch sets back and the brake drops into the sweeping center second wheel to prevent it from moving. When resetting the chronograph back to zero the hammer drops back into place resetting the counter wheels back to zero, as the hammer drops in place it will engage into the brake and intermediate counter ratcheting lever to move them out of the way.
When you stop your watch the brake engages and the sweeping center seconds jumps back. It might be the brake as it engages the center sweeping wheel.
I think this is how it all works, I'm mot sure on terminology but I'm sure someone will correct me and will be able to explain your issue.

 

Could you take a video on the movement as you engage and stop the chronograph?
The hammer might have slight bend into it and it hits the sweeping center wheel before the break engages.
A video of the movement will help one of the watchmakers on here to help identify the issue.

 

Have you let it run a full minute so the minute counter ticks over? If so, does it also move when you press stop?

 

Thanks-

Yes- The watch is keeping time well. The minute counter ticks over properly at 1 minute and the stop second hand does jump on stop in this situation as well (always jumps backward and sometimes up to 5 seconds or more). I can take a video of the movement this evening.

I can likley still get watch back to seller- so trying to determine severity of the issue

 

What I am asking is if the minute recorder hand also moves back...

 

No- The minute recorder seems to be working fine. Also when stopping it a few seconds past 12:00- it never jumps back past 12:00