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This is a genuine circuit board assembly (coil block) for the MIYOTA 5Y30 quartz movement. The 5Y30 is a classic 3‑hand (hours, minutes, seconds) quartz movement commonly found in various ladies‘ watches and fashion timepieces. This circuit board assembly serves as the “brain” of the movement, consisting of a quartz crystal oscillator and an integrated circuit, responsible for generating a precise time base signal and driving the stepper motor.
It is ideal for repairing movements that have failed due to water ingress, battery leakage, or aging electronic components.
| Parameter | Specification |
|---|---|
| Compatible Movement | MIYOTA 5Y30 (3 hands: hours, minutes, seconds) |
| Movement Size | 5 ½‴ × 6 ¾‴ (approx. 15.75 × 13 mm) |
| Movement Height | 2.54 mm |
| Accuracy | ±20 seconds per month |
| Battery Life | Approx. 2 years |
| Battery | SR521SW / 379 (1.55 V) |
| Hacking Function | Yes (seconds hand stops when crown is pulled out) |
| Main Applications | Small ladies‘ watches, fashion accessory watches |
| Origin | Made in Japan |
Time Base：Built‑in quartz crystal oscillator + IC divider, generating a stable 32,768 Hz reference signal.
Stepper Motor Drive：The IC generates precise pulses to directly drive the stepper motor, powering the gear train.
Hacking Function：When the crown is pulled out, the IC logic locks the electronic pulse, instantly stopping the seconds hand for precise time synchronization.
EOL (Low‑Battery Indicator)：When battery voltage drops, the seconds hand jumps every 4 seconds, indicating battery replacement is needed.
Low Power Consumption：Battery life is approximately 2 years, with minimal power consumption.
Remove the hands, dial, and the defective movement to access the circuit board side.
Disconnect the old circuit board‘s contact springs from the battery contacts.
Clean the circuit board mounting slot and stator contact points – remove old oil and corrosion.
Place the new circuit board assembly into the mounting slot, ensuring precise alignment of the contact springs with the stator.
Secure the circuit board with its retaining screw, and verify that the rotor rotates freely and the coil/stator contacts are properly seated.
Install a new SR521SW / 379 battery and confirm correct polarity.
Reinstall the train bridge, dial, and hands.
Pull the crown to the time‑setting position and verify that the seconds hand stops (hacking function).
Important Note：Proper alignment of the contact springs with the stator is essential for hacking function. Incorrect alignment will prevent the motor from starting or disable the stop‑seconds feature. It is recommended to use a loupe to check contact alignment before tightening the retaining screw.
Q1: How can I tell if my 5Y30 circuit board is defective?
After installing a new battery, if the seconds hand still does not move or jumps every 4 seconds, and the battery contacts and gear train are normal, the circuit board assembly is likely defective. Use a multimeter to check coil resistance (normal range approx. 1.8 kΩ‑2.6 kΩ). An abnormal reading confirms the need for replacement.
Q2: Is this a genuine Miyota part?
Yes. This is a genuine MIYOTA factory part, made in Japan. All genuine parts carry the manufacturer’s mark and “Japan” origin marking. Purchase through authorized channels.
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