Jaeger-LeCoultre Caliber 916 – Technical Insights from Document 1161_JLC (Pages 3–4)

Pages 3 and 4 of the Jaeger-LeCoultre technical document 1161_JLC continue the in-depth breakdown of the Caliber 916, focusing on the automatic winding system, the alarm mechanism layout, and detailed part identification. This section is vital for watchmakers servicing or restoring a Memovox equipped with this historic high-beat alarm caliber.

Page 3 – Automatic Winding Mechanism

This page features an exploded diagram of the automatic module, illustrating:

• Rotor assembly: Mounted on a ball bearing, ensuring durability and quiet operation. The rotor is bidirectional, winding the main timekeeping barrel.

• Reduction gear train: This gear train connects the oscillating weight to the barrel ratchet wheel.

• Click and ratchet system: Prevents backspin and ensures proper torque delivery during wrist movement.

Important details include:

• Rotor axle lubrication point

• Reverser gear assembly—critical for bidirectional winding

• Bridges and screws clearly numbered, with part references used in later repair documentation

This layout allows for precise service steps, including removal order, reassembly torque control, and proper oiling.

Page 4 – Alarm Mechanism Components

Page 4 shifts focus to the alarm complication, highlighting:

• Alarm barrel and ratchet wheel (separate from the timekeeping barrel)

• Alarm hammer and spring: The hammer strikes a pin or resonance plate, producing the mechanical chime

• Alarm setting disc: Controlled by the secondary crown; it rotates a disc beneath the dial to select the activation time

• Trigger lever and on/off mechanism: Controls the coupling of the alarm gear train to the barrel

This section identifies the specific components involved in:

• Alarm winding

• Activation sequence

• Energy release when the alarm time is reached

Particularly important is the correct alignment of the alarm hammer and lever—improper positioning leads to weak or non-functioning alarms.

Key Technical Points from Pages 3–4

• The automatic winding system drives only the timekeeping barrel. The alarm barrel must be wound manually via the second crown.

• Alarm release is mechanically timed by the hour wheel’s finger interacting with the alarm disc.

• Servicing tip: Always test the hammer strike with the case back on, as resonance may vary without it.

• Lubrication caution: Minimal or no lubrication is applied to the alarm hammer pivot to avoid dampening the sound.

Summary

Pages 3 and 4 of document 1161_JLC provide crucial exploded diagrams and servicing insights for the two most complex sections of Caliber 916—the automatic winding system and the mechanical alarm module. These pages are indispensable for correct disassembly, cleaning, lubrication, and reassembly. Watchmakers must work precisely, especially around the alarm trigger components and winding gears, to preserve the unique sound and reliability of this iconic Jaeger-LeCoultre automatic alarm movement.