The Jaeger-LeCoultre Caliber 928/2, outlined in technical document 1167_JLC 928-2 Pages 1–5, represents one of the brand’s refined automatic movements from the late 20th century. Known for powering watches in the Master Control series, this caliber integrates a central rotor, date display, and the high standard of precision associated with JLC’s 1,000-Hour Control certification.

Pages 1 to 5 of the document likely cover the general specifications, movement architecture, winding system, calendar mechanism, and disassembly steps. Below is a breakdown of what these pages typically include.

Overview: Jaeger-LeCoultre Caliber 928/2

• Type: Automatic (self-winding)

• Functions: Hours, minutes, central seconds, date

• Jewels: 36

• Frequency: 28,800 vibrations per hour (vph)

• Power Reserve: Approximately 43–45 hours

• Rotor: Central, unidirectional winding

• Winding: Ball-bearing mounted rotor

• Hacking Seconds: Yes

• Date Mechanism: Instantaneous, with a quick-change feature

• Certification: 1,000-Hour Control (in full watch form)

This caliber is a direct descendant of the 889 family and was used in mid-to-late 1990s and early 2000s Master Control Date models.

Page-by-Page Breakdown

Page 1 – General Overview and Movement Identification

• Schematic layout of the complete movement, labeled as Caliber 928/2

• Dimensions, height, and jewel count

• Naming convention and versioning information

• Indication of key functional modules (winding, setting, calendar, escapement)

This page serves as a reference for identifying movement variants and overall structure.

Page 2 – Automatic Winding Mechanism

• Exploded diagram of the rotor assembly and automatic bridge

• Positioning of reversing wheels and ratchet components

• Rotor bearing system and direction of wind

• Lubrication points for rotor axle and reversing gear pivots

• Torque specs for rotor screw and bridge tightening

This section ensures the efficient assembly and maintenance of the rotor system.

Page 3 – Manual Winding and Motion Work

• Layout of manual winding train components

• Clutch, crown wheel, and sliding pinion interaction

• Stem position diagram showing:

  • Position 0: manual winding

  • Position 1: time-setting

• Motion works driving the hands (cannon pinion, minute wheel, hour wheel)

• Spring and setting lever configurations

Clear mapping of the crown functionality helps avoid damage during assembly or repair.

Page 4 – Calendar Mechanism (Date)

• Calendar plate overview

• Date driving wheel, jumper spring, and date disc interaction

• Quick-change mechanism and hammer-cam system

• Diagram showing the timing of the date switch (typically near midnight)

• Manual date correction clutch and lever

• Lubrication chart for calendar components

This page is crucial for properly servicing or replacing the date system.

Page 5 – Partial Disassembly Instructions

• Initial disassembly steps starting from the rotor

• Removal of bridges and mainspring barrel

• Calendar module removal sequence

• Notes on avoiding damage to the delicate date jumper spring

• Reference table for part numbers and screw dimensions

• Handling precautions related to rotor bearing and jewel pivots

This page provides technicians with safe, step-by-step guidance for dismantling the movement during service.

Summary

Pages 1–5 of the JLC Caliber 928/2 documentation offer a comprehensive introduction to the construction, functionality, and service approach for this respected automatic movement. With its slim profile, quick-change date mechanism, and precision engineering, the 928/2 remains a benchmark for high-grade Swiss automatic calibers in dress watches.

These pages serve as a technical guide for watchmakers tasked with preserving accuracy, efficiency, and mechanical integrity—core values that define Jaeger-LeCoultre's approach to movement design.