Seiko 6105B Technical Guide

Overview

The Seiko 6105B is an evolution of the renowned 6105A automatic movement, introduced in the early 1970s. It powered some of Seiko’s iconic dive watches, including the famous 6105-8110 and 6105-8119 models. The 6105B retained the robustness and reliability of its predecessor while incorporating refinements for improved durability and performance, making it a favorite among divers and collectors.

Specifications

• Caliber: 6105B

• Movement Type: Automatic mechanical with manual winding

• Jewels: 17 synthetic rubies

• Frequency: 21,600 vibrations per hour (3 Hz)

• Power Reserve: Approximately 44 hours

• Functions: Hours, minutes, central seconds, date complication

• Diameter: Approximately 27.4 mm

• Thickness: Approximately 5.5 mm

Movement Architecture and Components

Mainspring and Barrel

The mainspring stores energy either through manual winding or the automatic rotor, providing about 44 hours of power reserve.

Automatic Winding System

Features Seiko’s efficient bidirectional “Magic Lever” winding mechanism, allowing the rotor to wind the mainspring regardless of rotation direction.

Gear Train

Transmits energy from the mainspring barrel to the escapement and hands with precision and minimal friction.

Escapement

The Swiss lever escapement regulates energy release, maintaining steady timing accuracy.

Balance Wheel and Hairspring

Oscillates at 21,600 vibrations per hour, offering smooth hand movement and precise timekeeping.

Calendar Module

Includes a date complication, with manual adjustment via the crown.

Operation

The rotor, moved by wrist motion, winds the mainspring automatically. Energy flows through the gear train to the escapement and balance wheel, which oscillates to regulate timing. The date mechanism advances daily and can be manually adjusted as needed.

Servicing and Maintenance

• Lubrication: Proper application of oils and greases is essential at the mainspring barrel, gear pivots, escapement jewels, and rotor bearings.

• Common Issues: Wear of rotor bearings, mainspring fatigue, and possible wear on the calendar mechanism can impact performance.

• Maintenance Schedule: Regular servicing every 3 to 5 years is recommended, including cleaning, lubrication, and timing adjustment.

Summary

The Seiko 6105B is a rugged, reliable automatic movement that improved upon the successful 6105A. Its reputation for durability and precision has made it a sought-after caliber, especially for vintage dive watch collectors. With proper maintenance, the 6105B continues to offer accurate and robust performance.