Seiko Cal. 4M21A Supplement Vol. 2 - Power Resource Change

Seiko Cal. 4M21A Supplement Vol. 2 – Power Resource Change is a technical guide documenting the transition from original capacitor units to Seiko's new rechargeable battery technology for kinetic watches. This supplement clarifies the engineering shift affecting service and repair work on these movements. The guide compares the discontinued capacitor units (3029 114 and 3029 116) against the replacement rechargeable battery unit (3027 29R), presenting performance data including charge duration and swing counts so technicians understand the behavioral differences between old and new power resources. A detailed parts list with visual diagrams identifies the capacitor clamp and rechargeable battery clamp assembly (4225 552), showing how component markings distinguish between the two versions. Compatibility notes and mandatory replacement procedures ensure correct installation during service, preventing mismatches that could compromise movement function. Essential for watch repair professionals servicing 4M21A kinetic watches and troubleshooting power-related issues.