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FHF 120 Charles Aernie Ladies Movement - lots of victories


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I was given a small ladies watch to repair that was not working, not even cased. No clues as to what the issue was, but as long as I could get it going again without sinking a bunch of money on parts it would be considered a success.  I took the challenge.  Man what was I thinking?

Movement: FHF (FONT) 120, 17 Jewel  Fontainemelon SA

Type:  Ladies, manual wind.  Rate: 18,000 bph.  plate size: 6.75 x 8 ligne

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Findings:

Motion Works.  Able to change time smoothly, hands have good clearance. Switching between winding and time setting is not clean. Setting Lever arm was broken off and wedged in wheel train.  Prevented smooth flow of wheels so no power was coming form mainspring to escape wheel.  

No Case or crystal. Dial is scratched and dirty (will not be able to restore dial to original shape).  Movement is scratched as well and has fibers and dirt throughout. Watch was very dirty and oil had solidified causing it to become abrasive.  

Mainspring holds power, but is old and may not be able to sustain same level of power and there is no power compensating bend.  Arbor looks ok, scraping on barrel case, but due to prior repairs (not movement fault).  Teeth look ok.   Very old grease dried inside barrel, needed to be scrubbed to remove (not just placed in cleaning machine).  Mainspring is old style (no reverse bend to allow for sustained power).

Wheel Train:  No power on escape wheel when pallet fork removed, even after winding a few turns.  Loosened the train bridge and wheels started to turn again.  Found the culprit under the watch movement as the end of the setting lever arm had been lodged in amoungst the wheels.   Re attached bridge and good movement observed from wheel train when wound.  End shake minimal (might want to adjust jewel depth on a couple wheels if performance issues experienced).  Teeth all intact, pinions ok, and pivots not bent.  Jewels pivot holes in wheel train appear good.

Pallett Fork:  guard pin and pallet jewels looks good.  Banking pins not bent (part of plate).  Does not spring fully to opposite banking pin when tapped on end.  This turned out due to no power being transferred up wheel train.  Fair amount of end shake, and good drop depth on entry and exit.

Balance Complete:   Balance wheel is old school with timing screws (inconsistent material removed on opposite sides of wheel may lend to poising issue)  No Incabloc protection.  Balance rotates for about 5 -10 seconds before it stops.

Timing information:   Unable to obtain accurate timing until endshake problem resolved.  Amplitude low in some positions (new mainspring would help, and fixing jewel problem as well).  Cracked lower balance jewel provides problems.   Also showing signs that either one of the pallet fork jewels or impulse jewel needs to be adjusted.

 

Repairs:

Setting Lever Spring broken - replaced

Mainspring - needs new spring for better amplitude

Balance staff pivot broken - replaced

Balance spring twisted and bent - fixed

Balance spring collet to wide - need to be closed more for better fit

Timing washer required to poise balance

Double roller table - replaced

Lower Balance jewel chipped - needs to be replaced

jewels need to be adjusted to reduce end shake.

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All the parts disassembled prior to cleaning.   The mainspring should be replaced as it is retaining its compressed shape so has lost power and does not have the reverse curve for sustained power.

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Mainspring cover was scratched, and had grease in the barrel that was one of the worst I have seen.  Cleaned the barrel and cover manually before placing them in the ultrasonic.

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Broken setting lever spring and replacement.

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Ultrasonic cleaning machine.  5 minutes cleaning solution, spin off cleaner, then 4 minutes in rinse #1 and #2 (spinning off liquid between each jar).  Followed by 5 minutes in the drying chamber.  Pegged out the jewels in the main plate and bridges.  Did the balance separately since it had issues (normally would screw it in place on the plate for cleaning).

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Ready to start addressing the problem parts and reassemble.

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Straightened bent hairspring.  Removed stud, ran an oiler from the collet  (center) to the stud location on the edge to remove the tangle.  Made several bends to straighten the balance spring so flat, and so it had the right terminal curve, even gaps all around. 

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Balance staff pivot was broken as well.   Luckily had one in stock, so you can see the replacement staff in the background.  Balance spring stud is in pin vise, and stud pin is sitting next to balance spring in preparation for re-attachement.

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Threaded the spring through the stud, then passed the very small tapered pin next to lock the stud to the balance spring.  Still had to work on a the remaining bends after this picture was taken for the terminal curve and the slight bend before the stud.

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Lastly had to reduce collet opening since it would not firmly attach to the balance staff.  Another problem found and resolved.

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Removing the double roller table using the 18R inverto staking tools.

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Positioned staking tool roller table remover and pivot punch.  Placed the roller remover arm in the hole in the center of the staking tool base. Turning the knurled knob to gradually tighten the two blades of the remover so they were wedged between the bottom of the roller table and the balance arms.

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One VERY gentle tap and the double roller table removed, impulse jewel intact.

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Setting up the balance staff remover on the staking tool base, with the tip of the associated staff staking tool loaded and visible inside gap in tool.  (dark square floating above the broken pivot head).   The staff remover was tightened securely to prevent damage to the balance wheel.

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A couple more light taps and the balance staff passed through the balance wheel.  Surface of wheel arms in good shape.

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There are three possible balance staffs to pick from that vary only in overall length A and distance B.   The balance staff I used  was 2.77 mm in length.  (Could possibly try the 2.80 for less endshake)

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Attaching the new balance staff.  Using the rounded tip staking tool with hole just large enough for pivot to enter in order to create the rivet ridge first.  Then used the flot staking tool (seen to the left leaning against the base) to smooth over the ridged material created in the first step which secures the staff to the balance wheel.

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Not the slickest job, but this balance has a few miles on it.  The staff is firmly attached (does not twist in setting) and the balance arms were not warped because of the operation.

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Truing the wheel in calipers after staking.  It had a bit of a wobble, but after cinching up caliper ends over the pivots to protect them, and performing a few extremely gentle bends using my thumb, got the balance wheel true.  It is a solid wheel and the round was not affected but verified was true in the round as well.  Doesn't show up well in this picture, but there is an adjustable arm protruding out of the calipers next to the bottom right of the balance wheel.  This arm has a parallel surface you are aligning with the edge of the balance wheel to indicate if the wheel is running truly flat for the whole circumference as you rotate the balance and check for level.

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Reattached double roller table using staking tool.  Placed roller table over a hole in the die base that was big enough for the pivot, placed the balance staff (wheel attached) through the base of the roller table and tapped the roller table onto the staff.   Appears to be level and pivots look perfect now.

However, all is not well!   When I reattached the roller table, either I did not notice it had a problem before, or I was guilty of tapping one time too many to get it seated in place.  The top of the impulse jewel is below the safety roller table surface, which I did not immediately notice and which shows up later to be a problem for me.  😞

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Next was poising the wheel.  Gently pushed the balance wheel with a feather to get it to start rolling on the two ruby rails of the poising tool.  It had a heavy spot on one side as it always stopped at the same spot when spinning it gently on the leveled ruby poising tool.

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Added a timing washer under the timing screw on the opposite side.  Timing screw end is visible in the timing screw adjusting tool.  After that the wheel seemed to stop at random spots from that point on, so I was lucky not to have a long session.

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Re-attached hairspring collet (pressed on using flat tips of tweezers).

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Found the old broken pivot wedged in the balance jewel oil well and removed it.  The lower blalance jewel is chipped and needs to be replaced.  The end cap (not shown)  looked ok, no pitting.

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Balance wheel sits well dial down.  Can see the new timing washer on the left most timing screw (it is clear of touching anything) and the screw head is not protruding far enough to touch the plate.  Balance spring is sitting flat and in the regulator.   There is a bit too much endshake in the balance though.  I believe the balance jewels on the main plate may need to be moved in a bit.

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Fork end looks fine, along with the guard pin.  Banking pins seem straight, not sure how to tell if they are 90 degrees perpendicular, but nothing obvious showing.  (can still see the broken pivot in the jewel in the background)

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Wow is this timing ugly!   Attempting to adjust timing is futile until the jewels are replaced and adjusted.  Also believed there was an overbanking problem or with either the impulse jewel or one of the pallet fork jewels due to the staggered second timing line?

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Watch runs ok in dial down and vertical positions.  As soon as it moves towards dial up the balance stops.  The impulse jewel ends up on the wrong side of the pallet fork instead of being inside it.  Somehow the impulse jewel is jumping over the guard forks.  Initially I thought it was due to excessive endshake.

Here is an example of when the impulse jewel is jumping out of the pallet fork horn and sitting on the pallet horn .

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When it finishes it’s movement, the impulse jewel pushes off on the horn sending it back to the other banking pin and the watch stops running since it is now overbanked.

That is when NickelSilver informed me that the roller table appeared to be crushed (see the red background picture earlier), which explained the impulse jewel jumping over the pallet.   So I needed to replace the roller table.

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Instead of tapping it in, I decided to use the jewel lever attachment to press it in gently.

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Watched closely to make sure not to press any further once the gap between the roller table and the balance wheel was closed.  Once this was done, the overbanking issue was resolved and the watch would run in all positions.  🙂

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The pallet jewels appear to have a proper drop on either side of the pallet.  The jewels appear to have decent surfaces, and I later removed the pallet and cleaned the excess moebius  9145 off the rather greasy looking pallet stones.

So the very last step prior to demagnetizing the watch again and adjusting the beat and rate,  will be to replace the cracked balance jewel.

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To replace the jeweI I will be using the K&D staking tool set with a hollow ended jewel pusher and stump.  Just checking that the size of the pusher is ever so slighly smaller than the jewel, and the hole in the hollow stump is larger than the jewel.

After the jewel is out, I will double check it’s diameter by using a jewel reamer to test the hole size (the new jewel will be a fraction  larger than that reamer size).

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And take a depth reading off the micrometer on the staking tool prior to removing the old jewel so I can replace it at the same depth it was inserted to previously.

(Note:  These two example pictures had the balance bridge posing for me instead of the main plate to just illustrate the process I will do.  When working on the plate I need to push the jewel in from the inside of the watch plate for the balance jewel.

That wraps it up for this fix.  It was satisfying to have all the little victories making it past each challenge presented and was a good experience.  I still have to spend time adjusting the beat and rate and possibly the end shake, but the major work is complete.

Cheers.   Terry

 

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Hi clockboy, thank you for that very valid grounding comment, and I would normally agree with it.  However, I have trays of spare FHF120 /60 parts on hand that may never be used so there were no out of pocket expenses in this instance.

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 However, time was spent for the cost of experience.  This was the first time I had done many of these repairs. I had to get into the frame of mind to analyze what was causing the problems and the logical steps of what to check first, and putting theory into practice.  

Next time I get a job that requires any of these tasks it will hopefully take me less time, and I will have a better understanding of what I should be charging for the repair.

Thank you kindly for your feedback 🙂 , I appreciate all comments.

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2 hours ago, grsnovi said:

How long have you been working on watches?

It appears that you're a pro.

Thank you for the kind comment.  Many years ago my dad was a watchmaker and showed me the basics, but I followed a different career path.  A couple of years ago I picked it up again and started seriously studying and setting up my bench.  Along with my studies,  I am trying to spend a bit of time on the bench every day to gain experience. There is much to learn!  🙂 

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