--- description: Genuine Ronda 775 / 785 movement coil block. Normtech series. Essential for repairing quartz movements after leakage or corrosion. Swiss made. title: Ronda 775/785 Coil Block - Sofly image: https://www.soflypart.com/wp-content/uploads/2019/05/785CO.jpg --- [Skip to content](#content) * [ Home ](https://www.soflypart.com "Home") * [Products](https://www.soflypart.com/shop/ "Products") * [Watch Circuit & Coil](https://www.soflypart.com/product-category/watch-parts/circuit-and-coil/ "Watch Circuit & Coil") * [Watch Parts](https://www.soflypart.com/product-category/watch-parts/ "Watch Parts") * **Ronda 775/785 Coil Block** [![Ronda 775/785 Coil Block](https://www.soflypart.com/wp-content/uploads/2019/05/785CO.jpg.webp)](https://www.soflypart.com/wp-content/uploads/2019/05/785CO.jpg) [![Ronda 775/785 Coil Block - Image 2](https://www.soflypart.com/wp-content/uploads/2019/05/785COB.jpg.webp)](https://www.soflypart.com/wp-content/uploads/2019/05/785COB.jpg) # Ronda 775/785 Coil Block $3.00 You Saved | Brand | Choose an optionRonda![Ronda](https://www.soflypart.com/wp-content/uploads/2023/06/41.jpg)[Clear](#) | | ----- | ---------------------------------------------------------------------------------------------------- | ### Discount | Quantity | Discount (%) | Price | | -------- | ------------ | ----- | | 1 - 4 | — | $3.00 | | 5 - 9 | 5 % | $2.85 | | 10+ | 10 % | $2.70 | ### Discount | Quantity | Discount (%) | Price | | -------- | ------------ | ----- | | 1 - 4 | — | $3.00 | | 5 - 9 | 5 % | $2.85 | | 10+ | 10 % | $2.70 | Ronda 775/785 Coil Block quantity Add to cart x [ Checkout ](https://www.soflypart.com/checkout/) * repair Covers 99% of Repair Needs * Wholesale Discounts * Fast Global Shipping * 24/7 Customer Support ## Product Description The coil is the **core electromagnetic component** of the circuit assembly in Ronda 775 / 785 quartz movements. It precisely converts electronic pulses generated by the IC into magnetic energy to drive the stepper motor rotor, thereby moving the gear train and the hands. This is a **genuine Ronda part**, designed for movements where the original coil has failed due to moisture ingress, battery leakage, corrosion, or mechanical damage causing an open or short circuit. ## Technical Specifications | Specification | Ronda 775 | Ronda 785 | | ---------------------------- | ----------------------------------------- | ----------------------------------------- | | Compatible Movement | Ronda 775 series (Normtech) | Ronda 785 series (Normtech) | | Movement Size | 7 ¾‴ (approx. 17.2×17.2 mm) | 8 ¾‴ (approx. 20.0×20.0 mm) | | Fitting Diameter | 17.20 mm | 19.40 mm | | Overall Height | 2.50 mm | 2.50 mm | | Jewels Options | Swiss Made 5 jewels / Swiss Parts 1 jewel | Swiss Made 5 jewels / Swiss Parts 1 jewel | | Stepper Motor | Single‑phase bipolar | Single‑phase bipolar | | Fault Detection | EOL (seconds hand jumps every 4s) | EOL (seconds hand jumps every 4s) | | Typical Battery | 364 / SR621SW | 362 / SR721SW | | Max Theoretical Battery Life | Approx. 7‑10 years | Approx. 7‑10 years | | Anti‑magnetic Shielding | 18.8 Oe | 18.8 Oe | | Origin | Swiss Ronda factory | Swiss Ronda factory | ## Installation Instructions 1 Work on an ESD‑protected bench. Remove the movement, dial, and hands. 2 Unscrew the bridge that secures the coil and circuit block, and remove the bridge. 3 Gently disengage the old coil block, separating its contact points from the PCB. 4 Use a dust blower and isopropyl alcohol to clean the coil recess and PCB contacts. 5 Align the new coil with the positioning pins and press it gently into the recess; verify that its contacts mate securely with the PCB pads. 6 Measure the coil resistance with a multimeter (typical 1.8‑2.6 kΩ). An abnormal reading indicates a poor connection or defective coil. 7 Reinstall the bridge and screws. Insert a fresh battery (correct polarity) and verify that the seconds hand runs. 8 Reassemble the hands and dial, check for proper hand clearance, and perform a full water‑resistance test. ## Maintenance & Service Guide * **Failure Diagnosis**：If the seconds hand does not move after a new battery is inserted, measure the coil resistance (typical range 1.8–2.6 kΩ). An open circuit (∞) or a short circuit (very low resistance) indicates a defective coil. * **Emergency Repair of Broken Coils**：The broken conductor is impossible to locate without micro‑precision tools. Do not attempt to solder or “bypass” the coil; this will almost certainly melt the insulation and destroy the component. * **Intermittent Stoppage**：If the watch runs for a while and then stops, but restarts after tapping it or reinstalling the battery, the coil solder joint may have a cold joint. Replace the coil and re‑clean the contacts. * **Preventive Replacement**：Ronda does not specify a fixed replacement interval for coils. However, after a battery leakage incident, water damage, or heavy use beyond \~10 years, it‘s wise to inspect the coil and replace it preventively. ## FAQ **Q1: Is the Ronda 775 coil compatible with the Ronda 785 movement?** **A:No**. Although both belong to the Normtech family, the Ronda 775 and 785 calibers require different coil blocks. Their dimensions and stator configurations are not the same. Always purchase the coil that matches your specific movement. **Q2: How do I test whether the coil is broken?** **A:**Remove the battery and use a multimeter (resistance mode) to measure between the two coil contacts. A healthy coil typically reads 1.8 kΩ to 2.6 kΩ. An “OL” (open circuit) or a very low reading (short circuit) indicates a defective coil. **Q3: Can I solder a broken coil wire to repair it?** **A:Not recommended**. The extremely fine enameled wire used in Ronda coils cannot be reliably soldered by hand. The heat of the soldering iron will also melt the insulation on adjacent turns, ruining the entire coil. The only safe repair is to replace the whole coil block with a new genuine part. **Q4: If the coil is damaged, should I replace the whole movement or just the coil?** **A:Replace the whole movement is often the better choice.** A brand‑new Ronda 775 / 785 movement is quite affordable and comes fully assembled, guaranteeing factory accuracy and water‑tightness. A coil‑only replacement requires a high level of precision and does not eliminate the risk of a partially corroded PCB. ## Why Choose SOFLY Watch Parts? * Fast worldwide shipping within 3 business days. * Competitive pricing on Seiko/Hattori calibers. * 3,000+ watch movements and parts in stock. * Trusted by watchmakers worldwide. * Personalized sourcing support via **info@soflypart.com** or WhatsApp **+86 18620212114**. ##### Our Popular Items [ ![Zenith El Primero 18.0240.4021 Crystal](https://www.soflypart.com/wp-content/uploads/2022/07/DSC09824.jpg) ](https://www.soflypart.com/product/generic-zenith-el-primero-chronomaster-02-0310-400-sapphire-crystal-29-85mm/) ### [Generic Zenith El Primero Chronomaster 02.0310.400 Sapphire Crystal 29.85mm ](https://www.soflypart.com/product/generic-zenith-el-primero-chronomaster-02-0310-400-sapphire-crystal-29-85mm/) [ ![Breguet Classique 8067 Sapphire Crystal](https://www.soflypart.com/wp-content/uploads/2022/04/DSC09612.jpg) ](https://www.soflypart.com/product/generic-breguet-classique-5920-5907-sapphire-crystal-30-5mm/) ### [Generic Breguet Classique 5920/5907 Sapphire Crystal 30.5mm ](https://www.soflypart.com/product/generic-breguet-classique-5920-5907-sapphire-crystal-30-5mm/) [ ![Hattori VD54/VD53 Circuit Block Electronic Module](https://www.soflypart.com/wp-content/uploads/2024/03/Hattori-VD53-circuit.jpg) ](https://www.soflypart.com/product/hattori-vd55-vd57-circuit-block-electronic-module/) ### [Hattori VD55/VD57 Circuit Block Electronic Module ](https://www.soflypart.com/product/hattori-vd55-vd57-circuit-block-electronic-module/) [ ![](https://www.soflypart.com/wp-content/uploads/2026/06/ETA-caliber-2000-1471-stop-pinion.jpg) ](https://www.soflypart.com/product/eta-caliber-2000-1471-stop-pinion/) ### [ETA Caliber 2000-1471 Stop Pinion ](https://www.soflypart.com/product/eta-caliber-2000-1471-stop-pinion/) [ ![](https://www.soflypart.com/wp-content/uploads/2026/06/ETA-210.001-circuit.jpg) ](https://www.soflypart.com/product/eta-210-001-4000-circuit-block-electronic-module/) ### [ETA 210.001-4000 Circuit Block Electronic Module ](https://www.soflypart.com/product/eta-210-001-4000-circuit-block-electronic-module/) [ ![](https://www.soflypart.com/wp-content/uploads/2026/06/DSC00416-1.jpg) ](https://www.soflypart.com/product/generic-rolex-spring-bar-kit-90-pcs/) ### [Generic Rolex Spring Bar Kit 90 Pcs ](https://www.soflypart.com/product/generic-rolex-spring-bar-kit-90-pcs/) [ ![](https://www.soflypart.com/wp-content/uploads/2026/06/Cartier-caliber-1847-rotor.jpg) ](https://www.soflypart.com/product/cartier-caliber-1847-oscillating-weight-rotor/) ### [Cartier Caliber 1847 Oscillating Weight Rotor (return broken part) ](https://www.soflypart.com/product/cartier-caliber-1847-oscillating-weight-rotor/) [ ![](https://www.soflypart.com/wp-content/uploads/2026/06/Cartier-caliber-175N-circuit.jpg) ](https://www.soflypart.com/product/cartier-circuit-block-for-caliber-175n/) ### [Cartier Circuit Block For Caliber 175N ](https://www.soflypart.com/product/cartier-circuit-block-for-caliber-175n/) [ ![TAG Heuer Carrera Sapphire Crystal 34.5mm](https://www.soflypart.com/wp-content/uploads/2023/09/DSC01806.jpg) ](https://www.soflypart.com/product/generic-tag-heuer-link-cjf2114-sapphire-crystal-34-5mm/) ### [Generic TAG Heuer Link CJF2114 Sapphire Crystal 34.5mm ](https://www.soflypart.com/product/generic-tag-heuer-link-cjf2114-sapphire-crystal-34-5mm/) [ ![Omega 215.30.46 Crystal](https://www.soflypart.com/wp-content/uploads/2023/09/DSC01995.jpg) ](https://www.soflypart.com/product/generic-omega-seamaster-aqua-terra-22-13-41-sapphire-crystal-34-5mm/) ### [Generic Omega Seamaster Aqua Terra 220.13.41 Sapphire Crystal 34.5mm ](https://www.soflypart.com/product/generic-omega-seamaster-aqua-terra-22-13-41-sapphire-crystal-34-5mm/) * [![Panerai Radiomir 8 Days PAM00268 Crystal](https://www.soflypart.com/wp-content/uploads/2022/07/DSC09943.jpg)](https://www.soflypart.com/product/generic-panerai-radiomir-8-days-pam00268-sapphire-crystal-36-5mm/) Quick View [Add to Cart](https://www.soflypart.com/product/generic-panerai-radiomir-8-days-pam00268-sapphire-crystal-36-5mm/) Watch Parts [Generic Panerai Radiomir 8 Days PAM00268 Sapphire Crystal 36.5mm](https://www.soflypart.com/product/generic-panerai-radiomir-8-days-pam00268-sapphire-crystal-36-5mm/) $105.00 You Saved * [![Rolex Milgauss 116400 Crystal Gasket](https://www.soflypart.com/wp-content/uploads/2024/03/Rolex-crystal-gasket.jpg)](https://www.soflypart.com/product/generic-rolex-oyster-perpetual-31-177200-crystal-gasket/) Quick View [Add to Cart](https://www.soflypart.com/product/generic-rolex-oyster-perpetual-31-177200-crystal-gasket/) Watch Parts [Generic Rolex Oyster Perpetual 31 177200 Crystal Gasket](https://www.soflypart.com/product/generic-rolex-oyster-perpetual-31-177200-crystal-gasket/) $8.00 You Saved * [![Ronda 785 Cannon Pinion](https://www.soflypart.com/wp-content/uploads/2019/05/785M.jpg.webp)](https://www.soflypart.com/product/ronda-785-movement-cannon-pinion/) Quick View [Add to Cart](https://www.soflypart.com/product/ronda-785-movement-cannon-pinion/) Watch Movement Parts [Ronda 785 Cannon Pinion](https://www.soflypart.com/product/ronda-785-movement-cannon-pinion/) $1.30 You Saved * [![Rolex 3186-657 Jumping Hour Click](https://www.soflypart.com/wp-content/uploads/2021/03/DSC06801.jpg.webp)](https://www.soflypart.com/product/generic-rolex-3186-657-jumping-hour-click/) Quick View [Add to Cart](https://www.soflypart.com/product/generic-rolex-3186-657-jumping-hour-click/) Watch Parts [Generic Rolex 3186-657 Jumping Hour Click](https://www.soflypart.com/product/generic-rolex-3186-657-jumping-hour-click/) $18.00 You Saved * [![ETA 2824/2834/2836-705 Escape Wheel](https://www.soflypart.com/wp-content/uploads/2019/06/28escape.jpg.webp)](https://www.soflypart.com/product/eta-2824-2-2834-2-2836-2-movement-escape-wheel/) Quick View [Add to Cart](https://www.soflypart.com/product/eta-2824-2-2834-2-2836-2-movement-escape-wheel/) Watch Movement Parts [ETA 2824/2834/2836-705 Escape Wheel](https://www.soflypart.com/product/eta-2824-2-2834-2-2836-2-movement-escape-wheel/) $16.00 You Saved * [![Chinese Screw-On Quartz Clock Movement](https://www.soflypart.com/wp-content/uploads/2019/07/gclstm1.jpg.webp)](https://www.soflypart.com/product/chinese-screw-on-quartz-clock-movement/) Quick View [Add to Cart](https://www.soflypart.com/product/chinese-screw-on-quartz-clock-movement/) Watch Parts [Chinese Screw-On Quartz Clock Movement](https://www.soflypart.com/product/chinese-screw-on-quartz-clock-movement/) $5.50 You Saved * [![TAG Heuer WAZ2011 Crown Screw Down](https://www.soflypart.com/wp-content/uploads/2023/05/DSC01154.jpg)](https://www.soflypart.com/product/generic-tag-heuer-formula-1-calibre-5-waz2011-crown-screw-down-7-8mm/) Quick View [Add to Cart](https://www.soflypart.com/product/generic-tag-heuer-formula-1-calibre-5-waz2011-crown-screw-down-7-8mm/) Watch Parts [Generic TAG Heuer Formula 1 Calibre 5 WAZ2011 Crown Screw Down 7.8mm](https://www.soflypart.com/product/generic-tag-heuer-formula-1-calibre-5-waz2011-crown-screw-down-7-8mm/) $30.00 You Saved * [![Girard Perregaux Vintage 1945 25820 Crystal](https://www.soflypart.com/wp-content/uploads/2024/03/DSC09678.jpg)](https://www.soflypart.com/product/generic-girard-perregaux-vintage-1945-25820-sapphire-crystal-26-9mm/) Quick View [Add to Cart](https://www.soflypart.com/product/generic-girard-perregaux-vintage-1945-25820-sapphire-crystal-26-9mm/) Watch Parts [Generic Girard Perregaux Vintage 1945 25820 Sapphire Crystal 26.9mm](https://www.soflypart.com/product/generic-girard-perregaux-vintage-1945-25820-sapphire-crystal-26-9mm/) $70.00 You Saved * [![Rado Integral 538.0592.3 Crystal](https://www.soflypart.com/wp-content/uploads/2022/11/DSC00529.jpg)](https://www.soflypart.com/product/generic-rado-integral-538-0592-3-crystal-36mm/) Quick View [Add to Cart](https://www.soflypart.com/product/generic-rado-integral-538-0592-3-crystal-36mm/) Watch Parts [Generic Rado Integral 538.0592.3 Sapphire Crystal 36mm](https://www.soflypart.com/product/generic-rado-integral-538-0592-3-crystal-36mm/) $80.00 You Saved * [![Omega 3303/3313 Movement Wheel 72233033501005](https://www.soflypart.com/wp-content/uploads/2019/06/3303jsml.jpg.webp)](https://www.soflypart.com/product/omega-3303-3313-movement-chronograph-wheel/) Quick View [Add to Cart](https://www.soflypart.com/product/omega-3303-3313-movement-chronograph-wheel/) Watch Parts [Omega 3303/3313 Movement Chronograph Wheel 72233033501005](https://www.soflypart.com/product/omega-3303-3313-movement-chronograph-wheel/) $135.00 You Saved ```json {"@context":"https://schema.org","@graph":[{"@type":["Store","Organization"],"@id":"https://www.soflypart.com/#organization","name":"Sofly","url":"https://www.soflypart.com","logo":{"@type":"ImageObject","@id":"https://www.soflypart.com/#logo","url":"https://www.soflypart.com/wp-content/uploads/2019/12/Sofly-logo.png","contentUrl":"https://www.soflypart.com/wp-content/uploads/2019/12/Sofly-logo.png","caption":"Soflypart","inLanguage":"en-US","width":"180","height":"62"},"openingHours":["Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday 09:00-17:00"],"image":{"@id":"https://www.soflypart.com/#logo"}},{"@type":"WebSite","@id":"https://www.soflypart.com/#website","url":"https://www.soflypart.com","name":"Soflypart","publisher":{"@id":"https://www.soflypart.com/#organization"},"inLanguage":"en-US"},{"@type":"ImageObject","@id":"https://www.soflypart.com/wp-content/uploads/2019/05/785CO.jpg","url":"https://www.soflypart.com/wp-content/uploads/2019/05/785CO.jpg","width":"580","height":"580","caption":"Ronda 775/785 Coil Block","inLanguage":"en-US"},{"@type":"BreadcrumbList","@id":"https://www.soflypart.com/product/ronda-785-movement-coil-block/#breadcrumb","itemListElement":[{"@type":"ListItem","position":"1","item":{"@id":"https://www.soflypart.com","name":"Home"}},{"@type":"ListItem","position":"2","item":{"@id":"https://www.soflypart.com/product/ronda-785-movement-coil-block/","name":"Ronda 775/785 Coil Block"}}]},{"@type":"WebPage","@id":"https://www.soflypart.com/product/ronda-785-movement-coil-block/#webpage","url":"https://www.soflypart.com/product/ronda-785-movement-coil-block/","name":"Ronda 775/785 Coil Block - Sofly","datePublished":"2019-05-15T09:47:01+08:00","dateModified":"2026-05-24T13:46:30+08:00","isPartOf":{"@id":"https://www.soflypart.com/#website"},"primaryImageOfPage":{"@id":"https://www.soflypart.com/wp-content/uploads/2019/05/785CO.jpg"},"inLanguage":"en-US","breadcrumb":{"@id":"https://www.soflypart.com/product/ronda-785-movement-coil-block/#breadcrumb"}},{"@type":"ProductGroup","name":"Ronda 775/785 Coil Block - Sofly","description":"Genuine Ronda 775 / 785 movement coil block. Normtech series. Essential for repairing quartz movements after leakage or corrosion. Swiss made.","sku":"1103028","category":"Watch Parts > Watch Circuit & Coil","mainEntityOfPage":{"@id":"https://www.soflypart.com/product/ronda-785-movement-coil-block/#webpage"},"image":[{"@type":"ImageObject","url":"https://www.soflypart.com/wp-content/uploads/2019/05/785CO.jpg","height":"580","width":"580"},{"@type":"ImageObject","url":"https://www.soflypart.com/wp-content/uploads/2019/05/785COB.jpg","height":"580","width":"580"}],"url":"https://www.soflypart.com/product/ronda-785-movement-coil-block/","productGroupID":"1103028","hasVariant":[{"@type":"Product","sku":"1103028","name":"Ronda 775/785 Coil Block - Ronda","description":"Product Description The coil is the\u00a0core electromagnetic component\u00a0of the circuit assembly in Ronda 775 / 785 quartz movements. It precisely converts electronic pulses generated by the IC into magnetic energy to drive the stepper motor rotor, thereby moving the gear train and the hands. This is a\u00a0genuine Ronda part, designed for movements where the original coil has failed due to moisture ingress, battery leakage, corrosion, or mechanical damage causing an open or short circuit. Technical Specifications Specification Ronda 775 Ronda 785 Compatible Movement Ronda 775 series (Normtech) Ronda 785 series (Normtech) Movement Size 7 \u00be\u2034 (approx. 17.2\u00d717.2 mm) 8 \u00be\u2034 (approx. 20.0\u00d720.0 mm) Fitting Diameter 17.20 mm 19.40 mm Overall Height 2.50 mm 2.50 mm Jewels Options Swiss Made 5 jewels / Swiss Parts 1 jewel Swiss Made 5 jewels / Swiss Parts 1 jewel Stepper Motor Single\u2011phase bipolar Single\u2011phase bipolar Fault Detection EOL (seconds hand jumps every 4s) EOL (seconds hand jumps every 4s) Typical Battery 364 / SR621SW 362 / SR721SW Max Theoretical Battery Life Approx. 7\u201110 years Approx. 7\u201110 years Anti\u2011magnetic Shielding 18.8 Oe 18.8 Oe Origin Swiss Ronda factory Swiss Ronda factory Installation Instructions 1 Work on an ESD\u2011protected bench. Remove the movement, dial, and hands. 2 Unscrew the bridge that secures the coil and circuit block, and remove the bridge. 3 Gently disengage the old coil block, separating its contact points from the PCB. 4 Use a dust blower and isopropyl alcohol to clean the coil recess and PCB contacts. 5 Align the new coil with the positioning pins and press it gently into the recess; verify that its contacts mate securely with the PCB pads. 6 Measure the coil resistance with a multimeter (typical 1.8\u20112.6 k\u03a9). An abnormal reading indicates a poor connection or defective coil. 7 Reinstall the bridge and screws. Insert a fresh battery (correct polarity) and verify that the seconds hand runs. 8 Reassemble the hands and dial, check for proper hand clearance, and perform a full water\u2011resistance test. Maintenance & Service Guide Failure Diagnosis\uff1aIf the seconds hand does not move after a new battery is inserted, measure the coil resistance (typical range 1.8\u20132.6 k\u03a9). An open circuit (\u221e) or a short circuit (very low resistance) indicates a defective coil. Emergency Repair of Broken Coils\uff1aThe broken conductor is impossible to locate without micro\u2011precision tools. Do not attempt to solder or \u201cbypass\u201d the coil; this will almost certainly melt the insulation and destroy the component. Intermittent Stoppage\uff1aIf the watch runs for a while and then stops, but restarts after tapping it or reinstalling the battery, the coil solder joint may have a cold joint. Replace the coil and re\u2011clean the contacts. Preventive Replacement\uff1aRonda does not specify a fixed replacement interval for coils. However, after a battery leakage incident, water damage, or heavy use beyond ~10 years, it\u2018s wise to inspect the coil and replace it preventively. FAQ Q1: Is the Ronda 775 coil compatible with the Ronda 785 movement? A:No. Although both belong to the Normtech family, the Ronda 775 and 785 calibers require different coil blocks. Their dimensions and stator configurations are not the same. Always purchase the coil that matches your specific movement. Q2: How do I test whether the coil is broken? A:Remove the battery and use a multimeter (resistance mode) to measure between the two coil contacts. A healthy coil typically reads 1.8 k\u03a9 to 2.6 k\u03a9. An \u201cOL\u201d (open circuit) or a very low reading (short circuit) indicates a defective coil. Q3: Can I solder a broken coil wire to repair it? A:Not recommended. The extremely fine enameled wire used in Ronda coils cannot be reliably soldered by hand. The heat of the soldering iron will also melt the insulation on adjacent turns, ruining the entire coil. The only safe repair is to replace the whole coil block with a new genuine part. Q4: If the coil is damaged, should I replace the whole movement or just the coil? A:Replace the whole movement is often the better choice.\u00a0A brand\u2011new Ronda 775 / 785 movement is quite affordable and comes fully assembled, guaranteeing factory accuracy and water\u2011tightness. A coil\u2011only replacement requires a high level of precision and does not eliminate the risk of a partially corroded PCB. Why Choose SOFLY Watch Parts? Fast worldwide shipping within 3 business days. Competitive pricing on Seiko/Hattori calibers. 3,000+ watch movements and parts in stock. Trusted by watchmakers worldwide. Personalized sourcing support via\u00a0info@soflypart.com\u00a0or WhatsApp\u00a0+86 18620212114.","image":"https://www.soflypart.com/wp-content/uploads/2019/05/785CO-150x150.jpg","offers":{"@type":"Offer","description":"Product Description The coil is the\u00a0core electromagnetic component\u00a0of the circuit assembly in Ronda 775 / 785 quartz movements. It precisely converts electronic pulses generated by the IC into magnetic energy to drive the stepper motor rotor, thereby moving the gear train and the hands. This is a\u00a0genuine Ronda part, designed for movements where the original coil has failed due to moisture ingress, battery leakage, corrosion, or mechanical damage causing an open or short circuit. Technical Specifications Specification Ronda 775 Ronda 785 Compatible Movement Ronda 775 series (Normtech) Ronda 785 series (Normtech) Movement Size 7 \u00be\u2034 (approx. 17.2\u00d717.2 mm) 8 \u00be\u2034 (approx. 20.0\u00d720.0 mm) Fitting Diameter 17.20 mm 19.40 mm Overall Height 2.50 mm 2.50 mm Jewels Options Swiss Made 5 jewels / Swiss Parts 1 jewel Swiss Made 5 jewels / Swiss Parts 1 jewel Stepper Motor Single\u2011phase bipolar Single\u2011phase bipolar Fault Detection EOL (seconds hand jumps every 4s) EOL (seconds hand jumps every 4s) Typical Battery 364 / SR621SW 362 / SR721SW Max Theoretical Battery Life Approx. 7\u201110 years Approx. 7\u201110 years Anti\u2011magnetic Shielding 18.8 Oe 18.8 Oe Origin Swiss Ronda factory Swiss Ronda factory Installation Instructions 1 Work on an ESD\u2011protected bench. Remove the movement, dial, and hands. 2 Unscrew the bridge that secures the coil and circuit block, and remove the bridge. 3 Gently disengage the old coil block, separating its contact points from the PCB. 4 Use a dust blower and isopropyl alcohol to clean the coil recess and PCB contacts. 5 Align the new coil with the positioning pins and press it gently into the recess; verify that its contacts mate securely with the PCB pads. 6 Measure the coil resistance with a multimeter (typical 1.8\u20112.6 k\u03a9). An abnormal reading indicates a poor connection or defective coil. 7 Reinstall the bridge and screws. Insert a fresh battery (correct polarity) and verify that the seconds hand runs. 8 Reassemble the hands and dial, check for proper hand clearance, and perform a full water\u2011resistance test. Maintenance & Service Guide Failure Diagnosis\uff1aIf the seconds hand does not move after a new battery is inserted, measure the coil resistance (typical range 1.8\u20132.6 k\u03a9). An open circuit (\u221e) or a short circuit (very low resistance) indicates a defective coil. Emergency Repair of Broken Coils\uff1aThe broken conductor is impossible to locate without micro\u2011precision tools. Do not attempt to solder or \u201cbypass\u201d the coil; this will almost certainly melt the insulation and destroy the component. Intermittent Stoppage\uff1aIf the watch runs for a while and then stops, but restarts after tapping it or reinstalling the battery, the coil solder joint may have a cold joint. Replace the coil and re\u2011clean the contacts. Preventive Replacement\uff1aRonda does not specify a fixed replacement interval for coils. However, after a battery leakage incident, water damage, or heavy use beyond ~10 years, it\u2018s wise to inspect the coil and replace it preventively. FAQ Q1: Is the Ronda 775 coil compatible with the Ronda 785 movement? A:No. Although both belong to the Normtech family, the Ronda 775 and 785 calibers require different coil blocks. Their dimensions and stator configurations are not the same. Always purchase the coil that matches your specific movement. Q2: How do I test whether the coil is broken? A:Remove the battery and use a multimeter (resistance mode) to measure between the two coil contacts. A healthy coil typically reads 1.8 k\u03a9 to 2.6 k\u03a9. An \u201cOL\u201d (open circuit) or a very low reading (short circuit) indicates a defective coil. Q3: Can I solder a broken coil wire to repair it? A:Not recommended. The extremely fine enameled wire used in Ronda coils cannot be reliably soldered by hand. The heat of the soldering iron will also melt the insulation on adjacent turns, ruining the entire coil. The only safe repair is to replace the whole coil block with a new genuine part. Q4: If the coil is damaged, should I replace the whole movement or just the coil? A:Replace the whole movement is often the better choice.\u00a0A brand\u2011new Ronda 775 / 785 movement is quite affordable and comes fully assembled, guaranteeing factory accuracy and water\u2011tightness. A coil\u2011only replacement requires a high level of precision and does not eliminate the risk of a partially corroded PCB. Why Choose SOFLY Watch Parts? Fast worldwide shipping within 3 business days. Competitive pricing on Seiko/Hattori calibers. 3,000+ watch movements and parts in stock. Trusted by watchmakers worldwide. Personalized sourcing support via\u00a0info@soflypart.com\u00a0or WhatsApp\u00a0+86 18620212114.","price":"3","priceCurrency":"USD","availability":"http://schema.org/InStock","itemCondition":"NewCondition","priceValidUntil":"2027-12-31","url":"https://www.soflypart.com/product/ronda-785-movement-coil-block/?attribute_pa_brand=ronda"}}],"@id":"https://www.soflypart.com/product/ronda-785-movement-coil-block/#richSnippet"}]} ```