Seiko 5M23A – Technical Guide

Overview

The Seiko 5M23A is a Kinetic quartz movement introduced by Seiko in the mid-1990s. It is a member of the 5M Kinetic family and a direct successor to the 5M22A. The 5M23A continues Seiko’s innovation in hybrid timekeeping, combining the mechanical energy generation of an automatic watch with the accuracy and stability of quartz regulation. This movement was widely used in mid-range Seiko sport and dress watches and was designed for durability, serviceability, and practical day-to-day use.

Technical Specifications

Functional Details

Kinetic Charging System

The 5M23A features Seiko’s well-known rotor-driven power generation system. Wrist movement spins a rotor connected to a micro-generator, which charges a storage unit. This energy powers the quartz circuit and step motor.

• Capacitor-based models require replacement after 5–10 years.

• Modern upgrade to the MT920 lithium-ion cell is highly recommended for longer reserve and better stability.

Power Reserve Indicator (PRI)

• The 5M23A includes a PRI function, activated via a button at 2 o’clock.

• The seconds hand jumps ahead to indicate reserve:

  • 5–10 seconds → 1 day

  • 20 seconds → ~7 days

  • 30 seconds → ~1 month

  • 40+ seconds → full charge (~6 months)

Weak or no response = low charge or failed capacitor.

Quickset Calendar

• Pull crown to position 1 and rotate clockwise to adjust the date.

• No day-of-week function is included.

• Calendar rolls over automatically at midnight.

⚠️ Do not use quickset between 9:00 PM and 3:00 AM to avoid gear damage.

Reset Procedure (After Battery or Capacitor Change)

After replacing the energy storage unit:

1. Install the new MT920 cell or capacitor securely.

2. Use non-metallic tweezers to short the AC (All Clear) contact to the positive terminal of the cell for 2–3 seconds.

3. The movement will reset, allowing the step motor to resume normal operation.

Service & Maintenance Notes

• Capacitor Failure is common in older models. MT920 rechargeable cell is the preferred upgrade.

• Ensure correct polarity during installation; reverse polarity may damage the IC.

• Use anti-static tools when working near the integrated circuit and reset contact.

• Do not lubricate rotor or coil system unless instructed by Seiko-specific manuals.

• Always inspect gaskets and perform a pressure test after servicing.

Common Issues & Diagnostics

Watches Featuring the 5M23A

The 5M23A was used in a wide range of Seiko Kinetic 100M watches during the mid-to-late 1990s and early 2000s. Key identifiers:

• Case references: 5M23-6A09, 5M23-6B19, 5M23-6D00, etc.

• Branded with "Kinetic" on the dial and "5M23" on the case back.

• Typically stainless steel or titanium models with screw-down casebacks and sporty dress styling.

Summary Table

Conclusion

The Seiko 5M23A is a robust and practical Kinetic movement that merges mechanical innovation with quartz accuracy. It offers a long-lasting and sustainable timekeeping solution, especially when upgraded with a modern rechargeable cell. For collectors and wearers alike, a properly serviced 5M23A provides reliable, self-sustaining performance for years.