Seiko 1E50A – Technical Guide (High Quality)

The Seiko 1E50A is an ultra-thin quartz movement designed for ladies’ watches, specifically optimized for two-hand analog display (hour and minute only). It is part of Seiko’s 1Exx movement family, which was engineered to support minimalist, elegant designs requiring extremely slim watch cases. The 1E50A delivers high-accuracy timekeeping in a form factor that supports sleek styling with no compromise on reliability.

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1. Technical Specifications

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2. Key Features

• Time-only movement (hour and minute)

• No seconds hand = reduced battery drain and simpler construction

• Ultra-thin construction (~1.15 mm) – ideal for slim or bracelet-style cases

• No date or day complication

• Reliable quartz performance with minimal moving parts

• Designed for fashion watches, dress watches, and delicate case designs

• Very low maintenance

The 1E50A was developed to meet the demand for ultra-flat watches with pure simplicity and elegance.

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3. Time Setting Instructions

• Pull the crown out to the time-setting position

• Rotate the crown to adjust the hour and minute hands

• Push crown back in to resume timekeeping

Note: There is no stop-seconds function since the movement does not have a seconds hand.

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4. Movement Architecture

Main Components:

• Quartz oscillator (32,768 Hz crystal)

• Integrated circuit (IC) – divides frequency and drives step motor

• Step motor – emits one impulse per minute to rotate hands

• Motion works – cannon pinion, hour and minute wheels

• Crown setting mechanism – includes clutch, sliding pinion, and stem

• No calendar section – simplifies structure and minimizes thickness

This ultra-compact construction allows full functionality with maximum design freedom.

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5. Battery Replacement

Battery Change Procedure:

1. Open case back carefully (usually press-fit type)

2. Use plastic tweezers to remove old battery

3. Inspect and clean battery contact points

4. Insert a new SR521SW battery (+ side up)

5. Wait 10–15 seconds for hand movement to resume

6. Reset time and seal case (replace gasket if needed)

⚠️ Always use ESD-safe tools when handling the movement to avoid circuit damage.

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6. Common Issues & Solutions

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7. Applications

The 1E50A was primarily used in:

• Seiko ladies' bangle and jewelry-style watches

• Ultra-slim dress watches with minimalist dials

• No-date, no-second hand designs

• Watches with small, narrow case sizes (often under 20 mm wide)

These timepieces often included elegant elements such as:

• Gold-tone or silver bracelets

• Gem-set bezels

• Pearl or gloss finish dials

• Designer or Seiko Dolce/Lukia line models

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8. Service Notes

• No lubrication required – the movement is fully dry-running

• Handle carefully – ultra-thin baseplate and circuit are delicate

• Always replace the caseback gasket during battery service

• Avoid magnetic fields and static discharge during handling

• Movement replacement is often the most cost-effective repair method

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9. Conclusion

The Seiko 1E50A is a fine example of Seiko’s micro-quartz engineering for the fashion watch segment. With its thin profile, clean functionality, and dependable quartz performance, this movement enables elegant time-only watches that remain lightweight, stylish, and durable. While not service-intensive, with regular battery care, the 1E50A will continue to power delicate vintage Seiko designs with understated precision.

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