Seiko 2409A - Parts List
Seiko 2409A – Technical Guide
The Seiko 2409A is a mechanical, hand-wound movement with a date function, developed by Seiko in the mid to late 1960s. It belongs to the 24xx series of calibers, known for their reliability, simplicity, and affordability. The 2409A is a robust and serviceable movement, designed primarily for everyday manual-wind watches within the Seiko 5 and Sportsmatic lines. Though overshadowed by its automatic siblings like the 2406A, the 2409A remains a fine example of Seiko’s practical watchmaking.
1. Technical Specifications
| Feature | Details |
|---|---|
| Caliber | Seiko 2409A |
| Movement Type | Mechanical – Manual winding only |
| Functions | Hours, Minutes, Central Seconds, Date |
| Jewels | 17 |
| Beat Rate | 18,000 vibrations per hour (5 beats/sec) |
| Power Reserve | ~42 hours |
| Hacking Seconds | No |
| Calendar | Date (non-quickset) |
| Winding | Manual only – no automatic rotor |
| Diameter | ~27.6 mm |
| Thickness | ~4.5 mm |
2. Key Features
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Manual winding only, ideal for slim case designs.
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Durable gear train supported by 17 functional jewels.
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Simple date mechanism, set by advancing the time.
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No quickset, which increases mechanical reliability over time.
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Mid-beat movement (18,000 bph) for solid accuracy with lower wear.
The 2409A was especially suited for watches in which cost, simplicity, and reliability were top priorities.
3. Calendar Operation
Since the 2409A lacks a quickset date, setting the date requires rotating the hands through full 24-hour cycles.
Date Setting Instructions:
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Pull the crown to the time-setting position.
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Advance the hands past midnight to change the date.
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Repeat the 24-hour cycle until the desired date is shown.
⚠️ Avoid turning the hands backward across midnight. This can strain or damage the calendar driving finger or jumper.
4. Movement Architecture
Dial Side:
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Cannon pinion, hour and minute wheels, and calendar drive wheel
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Date wheel and calendar jumper (spring-loaded)
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Setting mechanism linked to stem and clutch
Back Side:
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Manual winding system with crown gear, ratchet wheel, and click spring
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Barrel and mainspring
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Gear train (center, third, fourth, and escape wheels)
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Pallet fork and balance wheel with hairspring
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Balance bridge and shock protection (usually Diashock)
5. Servicing Guidelines
Recommended Service Interval:
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Every 4–5 years
Service Steps:
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Disassemble dial, hands, and setting works
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Remove the gear train, barrel, and balance
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Clean parts in ultrasonic cleaner or manually (for hairspring)
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Inspect pivots, jewels, mainspring condition
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Lubricate barrel arbor, pivots, escapement, and calendar parts
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Reassemble and regulate using a timing machine
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Aim for ±20–30 seconds/day post-regulation
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