Jump to content
  • 0

FHF 96-4 erratic rate and amplitude after service


Question

I am new to the hobby and only on my 4th service of a watch.  The first 3 have gone without any issues.

The latest one being a FHF ST96-4 movement. 

I put it on the timegrapher (Weishi 1900) to check it after servicing and to regulate.  All looked good at first then i adjusted the rate and beat error as it was loosing a little.  During this the balance wheel stopped (i did not touch it), so i move the levers back and it started again with a very poor amplitude.   Small adjustment and all started working again.

When it runs now there is no consistency in the rate or amplitude.  can go from -6 to -36 every few seconds.  the amplitude also changes from 284 to 295. The Beat error is 0.0ms.  The change is not dramatic like -6 to -36 in one go but runs steady for about 20 seconds then changes to 0 gain for 4-5 seconds when it resumes the rate goes lower.  Odd is at some times it gains and goes back to -6 as though it was resetting itself.

 

This is the output from the timegrapher.   I am assuming at this point it is an issue with the balance wheel / CAP Jewels???

 

IMG_8732.thumb.jpg.1f63bac6bbc212d93726908c0f2ceafa.jpg

 

 

Below is another one i have done showing normal results after regulating.

IMG_8733.thumb.jpg.2109ba6f4962aac1a72ea72216ab1945.jpg

Link to post
Share on other sites

9 answers to this question

Recommended Posts

  • 0

Periodic eraticity if correspondes to the period of a gear in the train, either on its own teeth or pinion or both ,imperfect jewel or bent/damage arbour, damage may not be noticable under normal eye loupe magnification. 

 

 

  • Like 1
Link to post
Share on other sites
  • 0

Since the erratic nature did not show before I started to regulate, I figure it must have something to do with the balance wheel.   Just took it out to inspect under microscope but could not see any damage to pins, spring or impulse pin.

I have a spare movement (not serviced) with a complete balance.  Swapped it out and put back on timegrapher.  All looks ok.  -18s/d, 251 amp and 0.5ms beat error. Nice consistent reading.

 

Again, I can not see any difference or faults when comparing both of them under a microscope.  

Link to post
Share on other sites
  • 0
53 minutes ago, SPIGGOTT said:

Again, I can not see any difference or faults when comparing both of them under a microscope

Often times people with microscopes can see the dust on the pine needles in the forest but can't see the trees.

Then interesting on the timing machine you appear to have two separate lift angles?

Then what happens if you rotate the microphone so the crown is facing down what is that look like On the timing machine?

 

  • Like 1
Link to post
Share on other sites
  • 0
2 hours ago, SPIGGOTT said:

Since the erratic nature did not show before I started to regulate, I figure it must have something to do with the balance wheel.   

Imperfections across the terminal curve of hairspring, might change its coil configuration, causing intermitent sticking, fouling ....etc. 

Genterate more data please in various positions.

 

Link to post
Share on other sites
  • 0
2 hours ago, Nucejoe said:

Imperfections across the terminal curve of hairspring, might change its coil configuration, causing intermitent sticking, fouling ....etc. 

Genterate more data please in various positions.

 

So configuration of the coil might have changed as you moved the regulator arm, unlevel, coning so on.

Have you checked coil levelness from side view?

Link to post
Share on other sites
  • 0

Thanks everyone for the guidance.  I figured out the issue after watching some of Mark’s tutorials on the Unitas 6489.

He noticed that after servicing a new movement a few times he had the same issue with the balance.   It appears that it was not the balance at all but a few marks where it attaches to the main plate.  Basically screwdriver twists in the mainplate that lifted the balance slightly.

so when screwed down it was too tight and pushing against the cap jewels and springs.  This is why it was erratic. Must have put some further down pressure when I turned the regulator arms.

 

 


 

 

Link to post
Share on other sites
  • 0
1 hour ago, SPIGGOTT said:

when screwed down it was too tight and pushing against the cap jewels and springs. 

That is called endshake, very important to be right at least on the balance and escapement.

Link to post
Share on other sites


  • Recently Browsing

    No registered users viewing this page.

  • Topics

  • Posts

    • Nice work, I know the day ring can get brittle and crack while manipulating back into position during a service. Easy to guess how I came to find this out! good for me I had a ready supply of replacement 🙂    
    • The coil from @JohnD arrived in the post and set about modifying the metalwork to allow it to squeeze in place of the original. An hour or so of careful filing and Dremel work and it now fits like a glove. I also took care to ensure that the new wiring is double insulated with a few patches of Kapton tape a nylon bushing to replace one of the original brass nuts and some heat shrink sleeving ensuring that there is little chance of this ancient synchronous motor giving anyone a shock, even if the thing is dropped or the wires are pulled. I can't remember where I got the strange dayglo green cable ties from, but since nobody will see them, who cares about the colour. It got a good clean while it was apart as unsurprisingly it was filthy. The worm gears both had a thick pasty gunge on them that probably started life as either grease or oil. All of the bras surfaces were sticky and nasty.   Surprisingly it worked first time. After gingerly flicking the brass starter on the rear I let it run for about 10 minutes to see if it would overheat, but it was fine. No shocks, no smoke, no nasty electrical skid marks, no scary surprises. I then stripped it all down again and gave everything one more clean to ensure that I had removed all of the dust and filings from the modification and rebuilt it again gave it a proper oiling. This time though when I flicked it into life, it started to click ominously. My initial fear that the insulation might be breaking down and the coil arcing were unfunded, I has simply misaligned one of the gears and it was jumping. With that remedied I buttoned it all back up again and it is now sitting in my explosion containment test stand (the fire hearth) and whirring away with a low but pleasing hum. The patented tick also works. If you look carefully in the pictures of the mechanism you can see that it consists of a small steel blade that rides over some serrations on a brass wheel. Each time it falls off a tooth on the wheel, it clicks. The teeth are arranged to it ticks about twice per second. I've switched this off for the time being so I can listen out for any other strange noises it might produce. If testing goes well, then I'll case it back up and let it run, so I can see if it keeps good time. After that comes the tricky bit. Making a replacement for that wooden decorative trim. Here are some pictures of my test fitting of the coil, showing the modified brass top plate, the plastic spacer and some close up shots of the gearing.  
    • Thank you for your introduction and welcome to this friendly forum.
    • Have you demaged? Its a hairspring issue, sticking, rubbing, short length or wrong spring. So a bit of history might helps. 
    • Welcome to the forum Kieran.
×
×
  • Create New...