Lesson in humility -- Seiko 5106a project

[Levine98]

Hi,

I thought that once I tightened up the cannon pinion I had this buttoned up and running swell, only to find out that was not the case.

While there may be multiple issues, it seems the first one to deal with is a timing issue.

I have clocked it and it happens on a cycle, however I can use some help diagnosing the root cause.

The watch runs fine for appox 6 minutes, then the timing goes haywire. This lasts for approx 2 minutes, then the timing returns to normal for another (approx) 6 minutes.

I've attached pictures to clarify the issue--short lines are how long it doesn't time; long lines correspond to when it is running fine. I've also included snapshots of the corresponding timegrapher cycles.

I don't think this is my timegrapher, as I have numerous other movements that are timing fine and I noticed this earlier today when the watch appeared to be stopping periodically and/or losing time. 

I've looked under magnification while this was happening and do not see anything disrupting the balance wheel or other wheels as far as I can see (I have limited visibility at this point since I didn't take off the automatic works).

I did examine each wheel as I reassembled the movement (i cleaned it twice in fact), but I suspect I missed something since I was largely looking for debris and/or an obvious issue like a broken tooth. I'm assuming it isn't a jewel or bushing issue, since it happens on such a regular cycle. Given the freq of the cycle I gather the 3rd wheel is the place to start?

Thoughts?

Edited October 26, 2023 by Levine98
clarity/spelling

[nevenbekriev]

Could be some problem with the 3th wheel. Take a good look at it, see if it is bent or needs trueing - it's table may rubb somewhere.  When the period of bad work, You may put a dot on it with marker in a visible place - this way You will be able to observe if the bad period coincides with the same position of the dot.

Edited October 27, 2023 by nevenbekriev

[Levine98]

5 hours ago, nevenbekriev said:

Could be some problem with the 3th wheel. Take a good look at it, see if it is bent or needs trueing - it's table may rubb somewhere.  When the period of bad work, You may put a dot on it with marker in a visible place - this way You will be able to observe if the bad period coincides with the same position of the dot.

Yes, hoping that is it. I tore the movement down again and paid extreamly close attention to the third wheel—it is an odd configuration in that the 3rd wheel has three sprockets to it—top is attached to the shaft and drives the sweep second hand pinion, middle is a free floating spacer and the bottom drives the forth wheel. 

Anyhow I did pull out some debris from between the sprockets, and reassembled the movement. Right now running as it should be   I’m going to let it run 2 or 3 full wind cycles before buttoning up with calendar works and dial again to make sure the movement stays stable.  
 

There is one other issue, but I’ve decided to let it ride having put so much time into this project—whenever I try to get beat error below 1.0 using the stud armature, the timing and beat error goes way off.  So I’ve decided to just live 1.2 beat error, strong amplitude anf ~0-10 sec per day in all positions.