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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteThe Grand Seiko Caliber 9RA5 is an automatic Spring Drive movement: a mainspring supplies its power, while a quartz oscillator and electronic circuit regulate its timekeeping. Grand Seiko specifies an average accuracy of ±10 seconds per month and approximately 120 hours of power reserve. The SLGA015 is one complete watch built around the caliber.
What is the Grand Seiko Caliber 9RA5?
Introduced in 2020 for Grand Seiko’s 60th anniversary, the 9RA5 is an automatic Spring Drive caliber with manual winding. It is not a battery-powered quartz movement. A mainspring drives the gear train; a rotor connected to that train generates a small electrical charge for the quartz oscillator and electronic circuit that regulate the movement. Grand Seiko summarizes Spring Drive’s power source this way: “Its sole power source is a mainspring, which drives a series of gears.” Grand Seiko’s Spring Drive overview explains the system.
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The result is a seconds hand that moves in a continuous glide rather than ticking in discrete steps. The 9RA5 has a date display, a power-reserve indicator on the dial at 10 o’clock, and 38 jewels. Its crystal oscillator frequency is 32,768 Hz. These are caliber features; a finished watch’s size, water resistance, and other specifications depend on the model.
What do the 9RA5’s accuracy and five-day reserve mean?
Published accuracy: ±10 seconds per month
Grand Seiko’s current 9RA5 instructions specify average accuracy of ±10 seconds per month, equivalent to ±0.5 second per day. The estimate applies when the watch is worn on the wrist within a temperature range of 5°C to 35°C. It is a manufacturer specification, not an independent test result or a guarantee that every watch will show exactly that rate in every condition. See the 9RA5 movement instructions for the qualification.
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- Three-fold clasp with push button release
- Dual-curved sapphire crystal
- Power reserve display on the back
- Power resrve Approx. 72 hours(3 days)
Power reserve: approximately 120 hours
Grand Seiko specifies approximately 120 hours of power reserve—about five days—when fully wound. That gives the watch several days of operation off the wrist, but it is not a promise of identical running time in every situation: the instructions note that continuous operating time can be shorter depending on use. The dial indicator at 10 o’clock lets the wearer check the remaining reserve.
How does the 9RA5 regulate time?
In Spring Drive, the mainspring drives the mechanical gear train, while the Tri-Synchro Regulator controls its release using a rotor-generated electrical charge, a quartz oscillator, and an integrated circuit. The regulator’s precise control is what allows the seconds hand to glide. Grand Seiko describes the 9RA5’s high-precision package as combining a selected crystal oscillator, aged for three months, with an IC powered by a very small electric current.
Grand Seiko says a temperature sensor in the silicon-on-insulator IC takes 540 temperature readings per day and compensates for temperature-related variation in oscillator performance. This mechanism description and performance rationale come from the manufacturer’s Caliber 9RA5 movement page; the published accuracy figure remains a specification rather than an independent measurement.
What design features distinguish the 9RA5?
Offset Magic Lever
Grand Seiko says the Offset Magic Lever relocates the winding mechanism to reduce movement thickness while retaining winding efficiency. The arrangement contributes to the caliber’s slimmer design, rather than changing the way the wearer reads the time.
Two barrels and a revised gear train
The 9RA5 uses two barrels of different sizes. Grand Seiko attributes the approximately 120-hour reserve, while maintaining torque, to those barrels working with a revised gear-train ratio.
Rank #2
- STUNNING BLUE DIAL: this automatic men's watch features a deep blue, pressed pattern and gloss finish surrounded by a stainless steel watch case
- AUTOMATIC: these self-winding, automatic men's watches are powered by your movement, with a power reserve of 41 hours
- STAINLESS STEEL: features a durable stainless steel watch case and bracelet with see through caseback
- WATER-RESISTANT: these men's wrist watches are water-resistant down to 50 meters
- 4R35 CALIBER: equipped with the reliable caliber 4R35 automatic movement, this accurate men's watch keeps precise time
One-piece center bridge
Grand Seiko says the one-piece center bridge supports strength, durability, and shock resistance. These are design claims about the movement, not a substitute for a particular watch’s case construction or stated water resistance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How does the 9RA5 compare with the 9RA2?
The related 9RA2 followed in 2021. Grand Seiko describes both as automatic movements with a 120-hour reserve and ±10 seconds per month stated accuracy. Their most readily visible difference is the reserve indicator’s location.
| Movement | Power reserve | Stated accuracy | Power-reserve indicator |
|---|---|---|---|
| 9RA5 | Approximately 120 hours; Grand Seiko specification | ±10 seconds per month; Grand Seiko average-rate estimate | Dial, at 10 o’clock |
| 9RA2 | 120 hours; Grand Seiko description | ±10 seconds per month; Grand Seiko description | Case back |
Grand Seiko’s technical history of Spring Drive covers the release sequence and comparison. The movement comparison does not establish how any two finished watches wear: case dimensions, dial layout, and intended use must be checked model by model.
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Which watch uses the 9RA5?
Grand Seiko SLGA015
The SLGA015 is a concrete example: Grand Seiko identifies it as a Spring Drive diver’s watch powered by Caliber 9RA5. The manufacturer lists a 43.8 mm case diameter, 51.5 mm lug-to-lug length, 13.8 mm thickness, high-intensity titanium exterior, 200 m / 660 ft water resistance, and approximately 120 hours of reserve. The dimensions and water resistance describe the SLGA015, not the 9RA5 caliber in isolation. Consult the SLGA015 model page for its listed specifications, and check the relevant regional page for local details and current availability.
For a marketplace search, “Grand Seiko SLGA015 watch” is a specific product phrase. A marketplace result by itself does not establish that the seller is authorized or that the price, stock, or offer is current; verify those details with the seller and Grand Seiko’s regional information.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
