Landeron 51 Chronograph resets incorrectly

[BrehmerR]

Hi all watch lovers!
I am currently working on an absolutely beautiful landeron 51. 
I am having an issue with the chronograph however. When running the chrono for less than 30 seconds, everything works fine. However, when the seconds hand passes the 30 second mark and I reset it after, the chrono seconds hand resets a second too far back and the chrono minute hand doesn't reset correctly either. If you then start the chrono, let it run for 5-10 seconds and then reset it, they reset nicely.
The pictures below show what I mean. The first picture is where the hands are reset incorrectly. 
Does anyone have an idea of what the issue could possibly be?

thanks alot(:

[clockboy]

At a guess the hand is not tight on its arbour. 

[BrehmerR]

2 minutes ago, clockboy said:

At a guess the hand is not tight on its arbour. 

Thanks for the quick reply!
I already checked this though. The previous hand was slightly loose so I got this one which fits perfect. I would guess there is something wrong with the hearts or the reset hammer?

[clockboy]

OK I have not serviced many Chronographs but normally when fitting the hand the hammers have to be engaged by keeping pusher engaged. This is when the correct choreograph movement holder makes it easier. 
 

this very subject has been covered previously on this forum.

 

Edited September 9, 2022 by clockboy

[BrehmerR]

16 minutes ago, clockboy said:

OK I have not serviced many Chronographs but normally when fitting the hand the the heart has to be engaged by keeping pusher engaged. This is when the correct choreograph movement holder makes it easier. 

I usually don't do that but that does make very much sense. Keep in mind, I am still an amateur watchmaker. 
I am thinking that this is not the specific issue here though. The watch is functioning perfectly in literally every way except for that specific part of resetting after the 30 second mark. I understand it might not be so easy without being able to really have a look at the movement. I will provide some pictures of the movement later if anyone sees that as helpful.

Once again, thank you for teaching me that tip though(:

Firstly, Here are som pictures of the reset hammer. They look fine to me. Maybe someone more experienced can say something else?

Secondly, here are the seconds chrono wheel when the chrono is reset correctly opposed to when reset incorrectly. It is apparent that the seconds wheel is indeed reset in two different positions, yet when I turn them the slightest bit, they move the hammer indicating that it indeed is "reset correctly". 

Lastly, here are some pictures of the finger in the two different reset positions. When reset correctly, the finger is positioned in front of the teeth like it should be. However, when reset incorrectly, the finger is behind the tooth wich then pushes the chrono minute wheel one step when started.  

[praezis]

Looks like the finger on the chr.-runner touches the sliding gear wheel on reset. Try to move (turn) this finger a bit.

Frank

[BrehmerR]

8 minutes ago, praezis said:

Looks like the finger on the chr.-runner touches the sliding gear wheel on reset. Try to move (turn) this finger a bit.

Frank

Do you mean that I should move the finger on the chrono runner itself? Permanently change it's angle?

[praezis]

Yes. But first check if it really is touching by slowly moving the hammer to reset.

Frank

[JohnR725]

just in case you don't have the service manual one can be found here

http://www.clubderelojeria.com/archivos/01LANDERON51.pdf

 

 

[Jon]

This is slightly different from the Landeron 51, as this is a Landeron 248, so the eccentric studs might be different, but the principles are the same. Before thinking about moving the dart finger, I would ensure the minute register mechanism is set up properly. The slides will help understand the theory as well as the practical application. You have to understand how this works before adjusting anything, as turning an eccentric stud and not knowing what the result will be is asking for problems!

These are just a few slides from one of the lessons. There are many other ways to adjust the chronograph work that aren't in these few I have posted, as there are over 300 slides in the Landeron 248 lessons I wrote with the aid of the Ensemble-o-graf drawings. They are a great aid to understand chronographs.

 The position of the dart finger is incorrect in the photo you posted. It needs to be on the other side of that tooth of the sliding gear. Here's a picture of how the dart tooth should be almost touching the sliding gear tooth, so it travels almost 360 degrees before turning the sliding gear and minute register.

If you set the minute register mechanism properly, it may change the position of the teeth on the sliding gear so the dart finger is on the correct side when starting the chronograph, or you may find that you need to turn the dart tooth, as @praezissuggested.

Edited September 9, 2022 by Jon

[KarlvonKoln]

@Jon, I can't thank you enough for posting those slides.  I have serviced chronographs before, including one of my own, but I still feel like a beginner at it.  Since I hardly ever work on them, I've picked up some non-running chronograph movements to practice upon.  Those slides made my understanding quite a bit clearer, as well as helping with some of the part names that I didn't know.  So again, thanks for that.  Much appreciated.

[BrehmerR]

7 hours ago, KarlvonKoln said:

@Jon, I can't thank you enough for posting those slides.  I have serviced chronographs before, including one of my own, but I still feel like a beginner at it.  Since I hardly ever work on them, I've picked up some non-running chronograph movements to practice upon.  Those slides made my understanding quite a bit clearer, as well as helping with some of the part names that I didn't know.  So again, thanks for that.  Much appreciated.

Totally agree!
I am just like you so these sheets are incredibly helpful. When I get some more spare time I will sit down and go at it at the watch. I will keep you updated!

[BrehmerR]

The watch is now running perfectly! Like I was told, I rotated the finger slightly which did the trick. I also had to tighten the chrono seconds hand since it was sitting a little loose after having been taken off and put back on. 
Once again, this forum delivers. I am just as amazed at the help everyone here can provide every time. Truly amazing. 
I thank all of you who helped me with this project(;

Thanks!

[Jon]

If anyone wants to learn how to service chronograph movements, I teach this in South London. I also teach servicing manual wind and automatics, such as the ETA 2824-2 and Seiko 5 7S26C, amongst others.

As you can see from the few slides I posted, the theoretical and practical aspects are explored in depth in a small class of four. I've just started the term on Monday with a class of four beginners, who are currently working on a ETA 6497-2

If anyone is interested, send me a message.

I hope I'm not infringing any rules by saying all that?