Watch stops exactly every 10 minutes

[Simeon]

I have a Felca Skymaster with an ETA 2370 movement that I am getting ready to service. The watch has a habit of stopping almost exactly every 10 minutes. A tweak of the winding stem and it starts again. The second hand stops in pretty much exactly the same spot but will run through there happily for the rest of the time. It will do this for a few occasions and then work without break for a longer period.

I am guessing that there is some crud somewhere n the train. Likely the third wheel for the rotation speed? The 'boost' of torque from the wind pushes through the crud and it runs happily until the wheel has made a full revolution and comes back to the crud.

I guess it can also be damage to one or more of the teeth on the wheel. This seems less likely as the stopping is not consistent, as it will periodically run well. 

 

Is there anything else I should be looking out for?

[Waggy]

Have a look at the 'tail' on the seconds hand, is it catching on the hour hand? Also have a look at the minute hand, is it catching on the index, there are 4 positions without an index (12, 3, 6 and 9) so the minute hand may clear these and then stop on the next rectangular index ie 10 mins.

[AndyGSi]

Looking at you photo and as @Waggy said, it does appear that the minute hand is catching on the markers.

[Simeon]

2 hours ago, Waggy said:

Have a look at the 'tail' on the seconds hand, is it catching on the hour hand? Also have a look at the minute hand, is it catching on the index, there are 4 positions without an index (12, 3, 6 and 9) so the minute hand may clear these and then stop on the next rectangular index ie 10 mins.

 

8 minutes ago, AndyGSi said:

Looking at you photo and as @Waggy said, it does appear that the minute hand is catching on the markers.

No, I initially thought it could be the hands clashing but looking up close with a loupe, I can see the second hand has clearance from the minute hand along its full length, ncluding the tail.  Slowly rolling the minute hand over each index on the dial, I can see daylight between the hand and the index.  The hands are curved down at the tips but they are definitely not making contact.

The hands would also have to be moving up and down in order to allow it to run for the 10 or so minutes before stopping again with the second hand in exactly the same position.

[AndyGSi]

Try removing it from the case and see how it runs then.

[nickelsilver]

Do you have a pic of the movement? It's suspicious that the seconds hand is stopping in the same place. If this has the typical wheel on extended pivot of the 3rd wheel driving a seconds pinion in the center, I would check there.

[Waggy]

Easiest thing to do is to remove the canon pinion, it keeps ticking, problem is on the dial side, stops then its on the movement side 

[Nucejoe]

 I uncase the movement, and check it for running, as you remove each suspect like police does.

 

 

[SwissSeiko]

make sure the cannon pinion wheel, hour wheel, and minuet wheel are all meshing correctly and you have no missing teeth. Also, make sure the cannon pinion that's on the driving wheel isn't slightly loose. This doesn't have the standard cannon pinion. Its mounted on the movement side to a wheel

[Simeon]

I finally got back to this watch. I uncased the movement and ran it on the bench in a vertical position overnight - no stoppages. I took the opportunity to sand and polish the crystal, dust the dial and buff the hands while I cleaned and polished the case.

The movement is retained in the case by a thin wave spring washer that is located around the outside of the movement and provides pressure from the caseback.  This had been pressed into the caseback, so I took it out and relocated it back around the movement when re-casing it.

The watch has run fine for several hours on my wrist without stopping.  I think the movement may have been moving around inside the case and causing a clash somewhere.  Replacing it and refitting the spring may have secured it, preventing stoppages.

I am going to go ahead and service the watch but at least I know there isn't any unusual problems awaiting me.