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Eta 251.626 Service Walkthrough - The High-End Quartz Chronograph

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ETA 251.626 Service Walkthrough

 

The 251.626 is often found in mid to high-end quartz chronographs on the market today.


 

post-246-0-21774900-1433954377_thumb.jpg

 

It is a fairly complex quartz movement that has 5 motors, 2 with Red Coils, and 3 with Green Coils.

 

post-246-0-14247600-1433954380_thumb.jpg

 

To begin the service we start by removing the 3 Indicator Maintaining Small Plates, and Date Indicator.

A 1.4mm screwdriver is all the is needed for every screw on the movement.

 

post-246-0-09554900-1433954383_thumb.jpg

 

Here's a reference photo of the 3 screws for the Indicator Maintaining Small Plates.

 

post-246-0-36034400-1433954384_thumb.jpg

 

There are no more components to remove from the dial side of the movement.

 

post-246-0-80004400-1433954386_thumb.jpg

 

Once the movement is turned over, remove the 2 screws that hold the Magnetic Screen.

Once the Magnetic Screen is removed all the coils are very exposed, so work around these coils with great care.

 

post-246-0-13135500-1433954389_thumb.jpg

 

Here's a reference photo of the 2 screws for the Magnetic Screen.

 

post-246-0-29249400-1433954390_thumb.jpg

 

Next unscrew the 6 screws holding the Additional Printed Circuit and gently lift it off the movement.

Store the Additional Printed Circuit away separately and safe from the rest of the parts.

 

post-246-0-42061700-1433954393_thumb.jpg

 

Here's a reference photo of the 6 screws for the Additional Printed Circuit.

 

post-246-0-22637900-1433954396_thumb.jpg

 

Next we tackle the 2 trains with the red coils.

Right Side - Minute Counter

Left Side - Hour Counter

 

post-246-0-57264900-1433954399_thumb.jpg

 

The right and left trains contain different size wheels and should be kept separate for ease of assembly.

We shall start with the right side.

Remove the Minute Counter Bridge

 

post-246-0-00752700-1433954417_thumb.jpg

 

Next remove the Gear Train and the Rotor.

 

post-246-0-42856200-1433954420_thumb.jpg

 

Next remove the Coil and Stator.

Store the Coil away separately and safe from the rest of the parts.

 

post-246-0-55128100-1433954422_thumb.jpg

 

Here's a reference photo of the components and their corosponding screws.

Note the 4 spokes on the Minute Counting Wheel.

 

post-246-0-13643400-1433954424_thumb.jpg

 

Remove the Hour Counter Bridge.

 

post-246-0-11602700-1433954427_thumb.jpg

 

Remove the Gear Train and the Rotor.

 

post-246-0-85882700-1433954430_thumb.jpg

 

Remove the Coil and Stator.

Store the Coil away separately and safe from the rest of the parts.

 

post-246-0-24189500-1433954433_thumb.jpg

 


Here's a reference photo of the components.

Note the 3 spokes on the Hour Counting Wheel.

 

post-246-0-22417400-1433954436_thumb.jpg


 

Store these 2 trains in separate sections in your parts tray, and when cleaning store them in sparate parts containers.

 

post-246-0-19966200-1433954438_thumb.jpg

 

Next remove the Chronograph Bridge

 

post-246-0-46726000-1433954442_thumb.jpg

 

Now remove the Chronograph Wheel

 

post-246-0-59133900-1433954460_thumb.jpg

 

Unscrew the Green Coils and remove them.

Store the Coils away separately and safe from the rest of the parts.

 

post-246-0-88505800-1433954463_thumb.jpg

 

Here's a reference photo of the components and their corresponding screws.

 

post-246-0-98828700-1433954465_thumb.jpg

 

Remove the Train Wheel Bridge.

 

post-246-0-07090400-1433954469_thumb.jpg

 

Remove the Wheels of the Train.

 

post-246-0-66960800-1433954471_thumb.jpg

 

This is quite a complex train of wheels.

So to assist you I've cleaned up the rather cluttered schematic supplied by ETA and colour coded each wheel and it's location on the Main Plate.

 

post-246-0-14950200-1433954475_thumb.jpg

 

Here's a reference photo of the top of the wheels, also colour coded to assist you.

 

post-246-0-82163000-1433954477_thumb.jpg

 

And also the underneath of the wheels, also colour coded to assist you.

 

post-246-0-19681100-1433954480_thumb.jpg

 

Remove the Rotors and Stators.

 

post-246-0-49106400-1433954482_thumb.jpg

 

Unscrew the 3 screws that hold the Upper Plate and remove it.

 

post-246-0-72413100-1433954484_thumb.jpg

 

Here's a reference photo of the Upper Plate, Connector, and the corosponding screws.

 

post-246-0-20291200-1433954503_thumb.jpg

 

This now exposes the Electronic Module.

 

post-246-0-09830100-1433954507_thumb.jpg

 

Remove the Stop Lever/Switch

 

post-246-0-67983800-1433954509_thumb.jpg

 

Remove the Cannon Pinion with Driver.

 

post-246-0-16410600-1433954512_thumb.jpg

 

Then remove the Electronic Module.

 

post-246-0-43750900-1433954514_thumb.jpg

 

Pull out the Stem and Sliding Pinion.

Now store the Electronic Module away separately and safe from the rest of the parts.

 

post-246-0-20788400-1433954517_thumb.jpg

 

Remove the Minute Wheel, the Hour Wheel, and Contact Intermediate Wheel.

 

post-246-0-79851500-1433954519_thumb.jpg

 

Before we can remove the Date Indicator Driving Wheel, we need to pull back the Date Jumper.

Gently lift the tab (Yellow Arrow) until it's at plate level and pull it backwards.

This will pull the arm of the Date Jumper back and allow you to remove the wheel.

 

post-246-0-90690800-1433954523_thumb.jpg

post-246-0-98883400-1433954526_thumb.jpg

 

Here's a reference photo of the wheels.

 

post-246-0-95711000-1433954529_thumb.jpg

 

Lastly we need to remove the keyless work.

Unscrew the Setting Lever Spring and then remove the Setting Lever, Yoke, Driving Wheel, Internediate Setting Wheel No.1, and the Setting Wheel

 

post-246-0-99477000-1433954545_thumb.jpg

 

Here's a reference photo of the Keyless Work.

 

post-246-0-67346700-1433954548_thumb.jpg

 

The movement is now completely disassembled.

 

post-246-0-97646300-1433954550_thumb.jpg

 

I hope you've enjoyed this disassembly walkthrough and found it's given you the information and confidence to tackle this tricky but rewarding quartz movement.

I will post the assembly procedures tomorrow, Lord willing :)

 

post-246-0-32007600-1433954553_thumb.jpg

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Lawson, when do you find time to sleep?

I know how long it takes me to put together a walk through and mine have only a fraction of the detail that yours do.

This is yet another excellent publication, many thanks for time and effort that you must put into them.

Your photography and presentation are absolutely of the highest.

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ETA 251.626 Service Walkthrough

Part 2

 

Assembly

 

We begin the assembly with the keyless work.

 

post-246-0-43133600-1433997578_thumb.jpg

 

Fit together the Setting Lever and Setting Lever Jumper.

 

post-246-0-20198200-1433997581_thumb.jpg

 

Then install the Driving Wheel, Intermediate Setting Wheel No.1, and the Setting Wheel

 

post-246-0-86640100-1433997583_thumb.jpg

 

Install the Yoke

 

post-246-0-52776400-1433997586_thumb.jpg

 

Then slide the saddle at the end of the Setting Lever Jumper Arm into the groove in the Intermediate Setting Wheel No.1.

You will have to then lift the Intermediate Setting Wheel No.1 slightly to position the Setting Lever Assembly as shown below.

 

post-246-0-75059400-1433997588_thumb.jpg

 

Then locate the Setting Lever and Jumper onto their respective posts and slots.

Once screwed down engage the position arm of the jumper onto it's post on the Setting Lever.

 

post-246-0-07645900-1433997591_thumb.jpg

 

Next install the Date Indicator Driving Wheel.

Remember that you need to slide back the Date Jumper

 

post-246-0-43849900-1433997594_thumb.jpg

 

Once the Date Jumper is back in position check that the spring arm is once again down in it's correct position.

 

post-246-0-96436400-1433997596_thumb.jpg

 

Install the Contact Intermediate Wheel, the Hour Wheel and then the Minute Wheel.

 

post-246-0-47150000-1433997599_thumb.jpg

 

Replace the Electronic Module, then fit the Sliding Pinion and the Stem.

 

post-246-0-77889800-1433997601_thumb.jpg

 

Install the Cannon Pinion with Driver.

 

post-246-0-53360700-1433997621_thumb.jpg

 

Replace the Stop Lever/Switch.

 

post-246-0-18071500-1433997625_thumb.jpg

 

Then gently place the Upper Plate back on the movement, making sure the Yoke and Setting Lever are positioned correctly, and that you do not disturb any of the other components underneath.

 

post-246-0-89920800-1433997627_thumb.jpg

 

Refit the bank of Stators and Rotors which have the Green Coils.

 

post-246-0-49098400-1433997630_thumb.jpg

 

Now we come to the trickiest part of this service: installing the Main Gear Train.

 

post-246-0-79567800-1433997947_thumb.jpg

 

To assist in the order in which to install the wheels I will give the part numbers, and colour code the text, to match that of the diagram above.

Start with the Third Wheel [210].

 

post-246-0-92505100-1433997632_thumb.jpg

 

Then the Additional Intermediate Wheel [204]

 

post-246-0-33655900-1433999408_thumb.jpg

 

Then the Second Wheel [224]

 

post-246-0-24413700-1433997637_thumb.jpg

 

Then the Intermediate Wheel [203]

 

post-246-0-82581800-1433997639_thumb.jpg

 

Then the Driving Wheel for Second Counter [8059]

 

post-246-0-03672500-1433997642_thumb.jpg

 

Then the Driving Wheel for Chronograph Wheel 60s [8060]

 

post-246-0-62638900-1433997644_thumb.jpg

 

And lastly replace the Counting Wheel for Seconds or Minutes [8027]

 

post-246-0-58565800-1433997666_thumb.jpg

 

Once the train is in place, take some time to tweak the wheels so that are standing up as straight as possible.

 

Remember that you have 10 pivots to align with their respective jewels, so taking some time to position the wheels and rotors now can save you a LOT of frustration fitting the Train Wheel Bridge.

I would go so far as to take a little break, have a drink, relax your muscles and mind before proceeding to the next step.

 

Fit the Train Wheel Bridge and align all the pivots to their jewels, and check the free running of all wheels before tightening down only the 2 rear screws.

 

post-246-0-99966200-1433997669_thumb.jpg

 

Install the Chronograph Wheel.

 

post-246-0-55950800-1433997672_thumb.jpg

 

Next fit the Chronograph Bridge and align the 2 pivot points to their jewels.

This has to be done without the ability to manipulate the wheels directly, so make sure you inspect the jewels with high magnification to be sure the pivots are in their holes.

And again, check the free running of the train.

 

post-246-0-03270800-1433997675_thumb.jpg

 

Replace the Connector

 

post-246-0-33547500-1433997677_thumb.jpg

 


Next we will install the small trains for the Counting Wheel, 1/10s and Hour Counters. 

These are the ones with the Red Coils driving them.

Remember that the wheels are specific for each train and should have always been separated ... DO NOT MIX THEM UP.

We shall begin with the right side.


 

Install the right side Stator and Rotor for the 1/10s Counter.

 

post-246-0-79666700-1433997679_thumb.jpg

 

Next replace the Driving Wheel for Counting 1/10s [8059/1]

 

post-246-0-70192300-1433997682_thumb.jpg

 

Then replace the Counting Wheel, 1/10s [8027/1]

Note this has 4 spokes to the wheel.

 

post-246-0-52406200-1433997686_thumb.jpg

 

Fit the Counting Wheel Bridge, making sure to align the pivots and test the free running before tightening.

 

post-246-0-10900500-1433997689_thumb.jpg

 

We repeat the process for the left side Hour/Minute Counting Train.

Install the right side Stator and Rotor for the Hour/Minute Counter.

 

post-246-0-41837300-1433997692_thumb.jpg

 

Replace the Hour/Minute Counter Driving Wheel [8630/1]

 

post-246-0-43733000-1433997806_thumb.jpg

 

Then replace the Hour/Minute Counting Wheel [8600/1]

Note this has 3 spokes to the wheel.

 

post-246-0-15927300-1433997810_thumb.jpg

 

Fit the Hour/Minute Wheel Bridge, making sure to align the pivots and test the free running before tightening.

 

post-246-0-26151100-1433997813_thumb.jpg

 

Fit the Red Coil to the right side Counting Wheel Assembly and screw down.

 

post-246-0-67566100-1433997815_thumb.jpg

 

Fit the Red Coil to the left side Counting Wheel Assembly and screw down.

 

post-246-0-96435900-1433997818_thumb.jpg

 

At this stage also screw down the 3 Green Coils.

 

post-246-0-17476500-1433997821_thumb.jpg

 

Refit the Additional Printed Circuit.

 

post-246-0-82019300-1433997823_thumb.jpg

 

Replace the Magnetic Screen.

 

post-246-0-68435600-1433997826_thumb.jpg

 

Secure the Battery Clamp.

 

post-246-0-19994900-1433997829_thumb.jpg

 

Then turn over the movement to the dial side.

 

post-246-0-75281300-1433997831_thumb.jpg

 

Fit the Date Indicator.

 

post-246-0-35097700-1433997939_thumb.jpg

 

And secure the Date Indicator with the 3 Indicator Maintaining Small Plates.

 

post-246-0-17748800-1433997943_thumb.jpg

 

Then fit the dial and hands and test all the functions of the movement.

 


 

The service is complete.

 

post-246-0-11005500-1433997946_thumb.jpg

 

As always, I hope this walkthrough was informative and instructive, and gives you the confidence to complete this service on your ETA 251.626

 

 

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Brilliant guide with great pictures and instructions. It might encourage me to have ago at solving a problem that seems to have defeated everyone I have asked so far. Perhaps some of you knowledgeable people can advise what is the problem cause.

My Tissot PR200 had it's  ETA 251.262 movement replaced and all seemed to work ok on initial checking but I did not have time to check all functions carefully.

It sat undisturbed for a couple of weeks and then I checked it more carefully.  I noticed then that the Minute register did not reset correctly after a timing event.

I readjusted it to the zero position as per setup instructions. After another timing  event and then zeroing the minute register it did not reset to Zero but to the 5 minute mark.  After further re-zeroing and timing events it did the same thing consistently. 

I checked it some days later and the problem was slightly different in that after re-zeroing and timing event resets the Minute register did not reset correctly and seemed to overshoot the zero reset point by a variable amount of between 3 and 12 seconds.

All the other functions seem ok.

Any ideas most welcome as I have no clue as to what produce these symptoms.  Many thanks

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      Unscrew (0.8 Driver) the Jumper Maintaining Plate and remove it.
       


       
      Do the same for the Date Indicator Maintaining Plate
       


       
      Carefully remove the Jumpers Spring, holding it with a piece of pegwood so it doesn't ping away.
       

       
      Next remove the jumpers for the day and date.
       


       
      The jumpers differ from one another, so here is a reference photo so you can see the difference.
       

       
      Remove the Date Indicator and place it in a safe place where it won't be damaged.
       

       
      The last piece to remove on the Date Platform is the Double Corrector
       

       
      Now unscrew (1.4 Driver) the Date Platform and gentle pry it from the movement.
       


       
      Be careful when removing this plate, as there is a fine spring pressed into the plate that can be easily damaged.
       


       
      Here is a reference photo of the screws that hold the Date Platform.
       

       
      Remove the Hour Hammer Spring, once again using the pegwood to hold the spring while removing the tension.
       

       
      Here is a reference photo of the correct orientation of the spring.
       

       
      Remove the Hour Counter Lock.
       

       
      Remove the Hour Hammer Operating Lever.
       

       
      Next is the Hour Hammer, be careful when removing this item so as not to damage the Hour-Counting Wheel.
       

       
      Now remove the Hour-Counting Wheel.
       

       
      Remove the Date Indicator Driving Wheel
       

       
      Remove the Day Star Driving Wheel
       

       
      Then remove the Intermediate Calendar Driving Wheel
       

       
      Remove the Hour Wheel
       

       
      Then the Minute Wheel
       

       
      Remove the Cannon Pinion, which does not require a puller.
       

       
      The last component to be removed on this side of the Main Plate is the Driver Cannon Pinion.
       

       
      To lift the Driver Cannon Pinion I used what Mark used, a set of hand lifter from Horotec (MSA05.007); but
      you can also use a Presto Tool (30636-1) which will also work well.
       

       
      The dial side of the movement is now complete disassembled.
      Flip the movement over and unscrew (1.5 Driver) the Oscillating Weight.
       


       
      To remove the Hammer Spring lift it up gently over the automatic work and move it inwards.
      This will move the tail of the spring in a clockwise motion to the opening in the slots, which will free the spring.
       

       
      Slide out the Clutch Spring.
       

       
      Here is a reference photo of this spring, and it's orientation.
       

       
      Remove the screws (1.4 Driver) for the Automatic Device Bridge, and gently pry it loose.
       


       
      Here is a reference photo of these screws for the bridge.
       

       
      Once the Automatic Bridge has been removed, the two wheels for the automatic work are able to be removed.
      Below is a reference photo of how the sit inside the bridge.
       

       
      We now begin to disassemble the chronograph section of this movement.
      Begin with removing the Hammer, 2 Functions.
       

       
      Next remove the Clutch 60s, 2 Functions.
       

       
      Then remove the Minute-counting Wheel, 30min.
       

       
      Remove the Chronograph Wheel 60s, 30min.
       

       
      Gently lift out the Oscillating Pinion, 60s.
       

       
      Here is a reference photo of the orientation of this pinion.
       

       
      Unscrew (1.4 Driver) the Chronograph Bridge and gently pry it off the Train Wheel Bridge.
       


       
      Remove the Ratchet Driving Wheel.
       

       
      Remove the Chronograph Wheel Fiction.
       

       
      Unscrew (1.4 Driver) the Operating Lever, 2 Functions.
       


       
      Unscrew (1.4 Driver) the Lock, 2 Functions.
       


       
      Next remove the Minute-counter Driving Wheel, 30min.
       

       
      Slide out the Operating Lever Spring, 2 Functions.
       

       
      This spring can be fitting in both directions; but only 1 way is correct.
      Here is a reference photo of it's correct orientation.
       

       
      Remove the Switch.
       

       
      Here I digress from the order the SwissLab document illustrates the order of removal.
      They show to remove the Chronograph Cam before removing the Hammer Cam Jumper.
      This in my opinion is not the best way, as all the force from the jumper is pressing on the cam whilst your trying to remove it, and could lead to damage.
      Instead I move the Chronograph Cam until it reaches the notch as shown in the photo below.
       

       
      Then lift the Hammer Cam Jumper up to the top of the Chronograph Cam, which will release it's tension.
      Then, just as you removed the previous hammer, rotate the jumper to the opening in the slots, which will free the spring.
       

       
      Now you can unscrew (1.4 Driver) and remove the Chronograph Cam safely without tension on it.
       


       
      RELEASE THE MAINSPRING TENSION
       

       
      Once the tension has been released, unscrew (1.4 Driver) and remove the Balance Cock.
       


       
      Then unscrew (1.4 Driver) the Pallet Bridge and remove the bridge and Pallets.
       



       
      Unscrew (1.2 Driver) and remove the Ratchet Wheel.
       


       
      Then remove the Crown Wheel.
       



       
      Unscrew (1.4 Driver) the Train Wheel Bridge and gently pry it off the Main Plate.
       


       
      Note that one of the screws is under the Operating Lever.  This needs to be moved out of the way to access this screw.
       

       
      The last level of this movement contains the train.
      Here is a reference photo of the wheel locations.
       

       
      Remove the Stop Lever.
       

       
      Remove the Great Wheel.
       

       
      Here is a reference photo of the underneath of this wheel.
       

       
      Remove the Third Wheel.
       

       
      Here is a reference photo of the underneath of this wheel.
       

       
      Remove the Second Wheel.
       

       
      Here is a reference photo of the underneath of this wheel.
      Note this has the long lower pivot.
       

       
      Remove the Escape Wheel.
       

       
      Here is a reference photo of the underneath of this wheel.
       

       
      Then remove the Barrel.
       

       
      This completes the removal of the train.
      Flip the movement over so we can complete the disassembly by removing the keyless work.
       

       
      Firstly, release the tension from the Setting Lever Jumper.
       

       
      Then unscrew (1.2 Driver) and remove the Setting Lever Jumper.
       


       
      These are unique screws with pointed ends, and below is a reference photo of them.
       

       
      This will also remove the Intermediate Setting Wheel.
       

       
      Next remove the Setting Wheel
       

       
      Then remove the Yoke.
       

       
      Remove the Setting Lever.
       

       
      Remove the Rocking Bar.
       

       
      Now pull out the Stem.
       

       
      Once the Stem is removed the Winding and Sliding Pinion should fall out of the movement onto your work mat.
       

       
      Disassembly of the 7750 is now complete
       

       
      If you've come this far, congratulation on completing the disassembly.
      Make sure you pegwood all the jewels and reinstall the Balance back onto the movement for cleaning.
       

       
      Assembly of the movement will be posted as soon as I complete the write-up.
       
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