Introduction to the Seiko 7F38A
The Seiko 7F38A is a rare and technically advanced high-accuracy quartz (HAQ) chronograph movement introduced in the early 1990s. A member of the elite 7F-series, the 7F38A was designed to provide exceptional timekeeping precision with ±20 seconds per year accuracy while incorporating chronograph functionality in a fully analog display.
Unlike many quartz chronographs of its time, the 7F38A features thermocompensation, metal gear construction, and a fully jeweled geartrain, making it highly durable and serviceable. Today, it is considered a collector-grade movement due to its precision engineering and low production volume.
Technical Specifications
| Feature | Description |
|---|---|
| Caliber Number | 7F38A |
| Movement Type | Quartz (thermocompensated, analog) |
| Jewels | 4 |
| Battery | SR927W (1.55V silver oxide) |
| Battery Life | Approximately 5 years |
| Accuracy | ±20 seconds per year |
| Display | Analog chronograph |
| Chronograph Function | 60-minute counter, center seconds hand |
| Calendar | Date (quickset, non-perpetual) |
| Hacking Seconds | Yes |
| EOL (End of Life Indicator) | Yes (2-second hand jump) |
The 7F38A was developed for users who demanded precision timing and reliable chronograph functions in a classically styled analog watch, without sacrificing long-term accuracy.
Chronograph Functions
The 7F38A offers a basic yet practical chronograph system, ideal for timing events up to one hour.
Chronograph Layout:
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Central chronograph seconds hand
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60-minute totalizer subdial, typically positioned at 9 or 12 o’clock
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Standard central timekeeping hands
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Date window, often located at 3 o’clock
Operation:
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Start/Stop: Press upper right pusher (Button A)
-
Reset: Press lower right pusher (Button B) after stopping
The chronograph hand moves in 1-second increments, typical for most analog quartz movements. Despite this simplicity, the movement is designed for long-term durability and serviceability, unlike many mass-produced quartz chronographs.
Time and Calendar Setting
Crown Functions:
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Position 0 (pushed in) – Normal timekeeping
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Position 1 (first click) – Quickset date adjustment
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Position 2 (second click) – Time setting (hacks second hand)
Avoid setting the date between 9 PM and 4 AM, as the date change mechanism may be engaged and susceptible to damage.
The calendar is not perpetual and will require manual correction for months with fewer than 31 days.
Battery Replacement and Reset Procedure
Battery Type:
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SR927W
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Expected life: Approximately 5 years
Low Battery Warning:
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Seconds hand jumps in 2-second intervals, signaling the end of battery life (EOL indicator)
Battery Replacement Steps:
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Remove the case back with the appropriate tool
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Extract the depleted battery using non-metallic tweezers
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Insert a fresh SR927W battery with correct polarity
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Reset the movement by shorting the AC contact to the battery’s positive terminal for 1–2 seconds using metal tweezers
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Confirm correct function of timekeeping and chronograph
After battery change, always inspect and replace the gasket as needed to preserve water resistance.
Servicing and Durability
The 7F38A is built for longevity, unlike many modern quartz chronograph movements that are designed for disposal rather than repair.
Serviceable Features:
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No plastic parts in the geartrain
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4 synthetic jewels placed in key locations
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Chronograph module can be accessed and lubricated
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Stepper motor is isolated for protection from dust and shock
Service Interval Recommendation:
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Every 8–10 years, or sooner if timekeeping drifts or chronograph function weakens
During service, the following steps should be performed:
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Inspect and clean chronograph reset levers and cams
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Lubricate pivot points and geartrain
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Clean and recalibrate calendar mechanism
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Test the stepper motor and oscillator output
Troubleshooting Guide
| Issue | Possible Cause | Solution |
|---|---|---|
| Chronograph doesn’t reset | Reset cam or pusher fault | Clean/lubricate or inspect reset system |
| Seconds hand jumps 2 seconds | Low battery | Replace battery |
| Watch stops after battery change | Circuit not reset | Perform AC reset |
| Date misalignment | Quickset error during restricted hours | Reset outside 9 PM–4 AM |
| Chronograph won’t start | Pusher or contact issue | Inspect case-side pushers and switches |
Final Thoughts
The Seiko 7F38A is a precision-engineered quartz chronograph that offers:
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±20 seconds per year accuracy
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Mechanical-grade construction with metal gears
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Chronograph functionality for up to 60 minutes
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Quickset calendar and hacking seconds
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5-year battery life with EOL warning
It represents Seiko’s commitment to quality quartz movements during a time when most manufacturers were shifting toward lower-cost, disposable designs. For those seeking a high-accuracy analog chronograph with exceptional build quality and ease of service, the 7F38A remains a rare and outstanding choice.
