Seiko 3423A – Technical Guide

The Seiko 3423A is a vintage manual-winding mechanical movement, purpose-built for ladies’ wristwatches. Part of Seiko’s compact 34xx caliber family, the 3423A offers precise timekeeping in a minimal, two-hand layout. Its small dimensions and traditional mechanical architecture make it suitable for elegant dress watches that prioritize thinness and simplicity.

This guide provides detailed information on the technical specifications, movement layout, servicing, and common troubleshooting for the Seiko 3423A.

Movement Overview

• Caliber Number: Seiko 3423A

• Type: Mechanical, manual-winding

• Functions: Hours and minutes (no seconds, no date)

• Size: 6¾ × 8 lignes (≈15.3 mm × 17.8 mm)

• Height: Approx. 3.15 mm

• Jewels: 17

• Beat Rate: 21,600 vibrations per hour (6 beats per second)

• Power Reserve: ~40 hours

• Hacking Feature: No

• Calendar Function: None

This movement was commonly used in Seiko’s women's dress watches during the 1970s, known for their reliability and longevity.

Mechanical Layout and Features

Though compact, the Seiko 3423A includes all the core components of a traditional mechanical caliber:

Main Components:

• Mainspring Barrel: Stores energy from manual winding.

• Gear Train (Center, Third, Fourth Wheels): Transfers energy to the escapement.

• Escapement (Pallet Fork & Escape Wheel): Controls energy release to the balance wheel.

• Balance Wheel with Hairspring: Oscillates to regulate timekeeping.

• Shock Protection: Usually fitted on the balance staff (e.g., Seiko Diashock).

• Bridges and Plates: Made of nickel-plated brass, precision-machined for tight tolerances.

Its simplified two-hand design minimizes moving parts and allows for a thinner, more durable structure.

Service and Maintenance

Regular servicing is essential to ensure the Seiko 3423A continues to function reliably, especially as these movements are now several decades old.

Service Interval:

• Every 3–5 years (recommended)

Service Steps:

1. Disassemble: Carefully take apart the dial side, gear train, escapement, and mainspring.

2. Clean: Ultrasonic clean all metal parts (except balance and pallet fork – clean by hand).

3. Inspect: Examine pivots, jewels, and mainspring for wear or damage.

4. Lubricate: Use modern oils (e.g., Moebius) at pivots, escapement, and mainspring contact points.

5. Reassemble: Refit components precisely, ensuring minimal friction.

6. Regulate: Adjust beat rate and amplitude using a timing machine.