The ETA 9158, originally an ESA Dynotron movement later produced by ETA, represents a transitional electronic caliber from the 1970s. Introduced around 1975, it features an electronically controlled balance motor with a sweep second hand for smooth operation. This third-generation Dynotron measures 13 lignes (29mm diameter) and offers reliable accuracy at 28,800 A/h beat rate.
Key Specifications
Type: Electronic tuning fork/balance wheel hybrid, battery-powered quartz alternative.
Size: 29mm diameter, 6.2mm height, 7 jewels.
Functions: Hours, minutes, sweep seconds, day-date at 3 o’clock (often gold or blue disks).
Features: Electrical hacking for precise setting, shock-resistant elements.
Historical Context
Developed by Ebauches SA (ESA), the Dynotron family began with Cal. 9150 in 1967, evolving through 9154 to the 9158 by 1975. ETA continued production post-ESA merger, using it in watches like Jaz Divers and Hamilton models. It bridged mechanical and full quartz eras with minimal jewels for cost efficiency.
Technical Highlights
The movement employs a prominent balance wheel and compact electronics, including resistors and transistors. Troubleshooting involves checking current consumption and train friction, as noted in 1970s service bulletins. Spare parts remain available for vintage repairs, including wheels and pinions.
Modern Relevance
Today, ETA 9158 appeals to horology enthusiasts restoring 1970s divers or dress watches. Its hi-beat electronic design offers accuracy without stepping motors, preserving sweep motion. Collectors value it for rarity in brands like Jaz.
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Watch Parts Enquiry
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Stem, Crown, Hands & Spares might be available for this movement.
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