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The Valjoux 7750 Overhaul.

The Valjoux 7750 was first introduced in 1974 and is an automatic chronograph with hour recorder and date. Being relatively cheap to produce and extremely reliable, this movement has become widely adopted in various guises by many of the major watch manufacturers.

The 'Overhaul' of a 7750 'movement'.

Stage 1 - the 'Strip Down'.
Here the movement is stripped down to it's 75 constituent parts. Each part is then cleaned, check for wear and replaced if necessary. The parts are then laid out in preparation for re-assembly.

Parts of the 'movement' that are most commonly replaced, due to wear:

1. The Barrel.

2. The Rotor Bearing.

3. 3rd Wheel.

4. 4th Wheel.

5. The Minute & Hour Recording Wheel.

6. The Seconds Recording Wheel.

The 7750 stripped down to it's 75 constituent parts.

Stage 2 - the 'Going Side' assembly.
The movement has been assembled up to the 'going side'. The 'going side' is a watchmakers term for the watch movement assembly before the 'complications' (i.e. chronograph, automatic, moonphase etc.) are added.
This is a crucial stage of the overhaul because unless these adjustments are accurately completed the movement will not successfully drive the 'complications'.

All the endshakes of the train wheels must be adjusted and the escapement checked and lubricated. Most importantly, the balance hairspring must be adjusted to breath flat in the horizontal plane and breath evenly on expansion and contraction in the vertical. It must be set to beat evenly between the curb pins and when at rest it must sit equidistant between them.

The movement is now ready to be placed on the 'timing machine'.

KEY:

1. Movement assembled to 'going side' in the Movement holder.

2. Remaining parts:
Chronograph work;
Automatic work;
Date work.

Stage 3 - the Assembly of the Chronograph mechanism and the automatic work.
Once the movement has been checked and timed to within tolerance, the automatic and chronograph mechanisms are assembled.

On the 7750, the automatic and chronograph work is layered between two 'bridges'. Accordingly both mechanisms are assembled simultaneously.

It is important at this stage to ensure that the chronograph 'hammer' is seated squarely and evenly on both 'heart shaped cams', enabling the return to zero function to be even and accurate.

1. Movement with 'minutes & seconds' chronograph and automatic work assembled.

2. Remaining Parts.
Motion work
Date work
Hour recording and hour re-set mechanism

Stage 4 - The complete movement before 'dialling-up'.
The date work, motion work and hour recording mechanism have now been assembled and the date plate attached. The date ring is then placed in position.

This is facilitated by using the Valjoux movement holder, specifically designed for this calibre.

1. Valjoux Movement holder.

2. Remaining Parts.
Automatic weight;
Case clamps and screws

Stage 5 - 'Dialled Up'.
The overhaul is now complete.

The dial and hands are replaced and all chronograph recoring hands set to zero. The movement is now ready to be placed back into the case.

Once in the case the watch undergoes a four day test period for timekeeping, in accordance with the manufacturers specification.

The completed Valjoux 7750 overhaul.

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