Automatic Triple Calendar (Calibre 7751)
This Omega Speedmaster Triple Calendar, powered by the automatic calibre 7751 — a highly regarded and technically complex movement combining a chronograph, date, day, month, and moonphase — arrived at our Geneva workshop for a full service.
The owner reported several malfunctions, including unstable pushers, issues with the automatic winding system, excessive play in various components, and multiple anomalies within the calendar mechanism.
To ensure complete transparency, we detail below the diagnostic findings, the interventions performed, and the results obtained during this Omega restoration.
Diagnostic Upon Reception
Based on the tests carried out in our workshop and the observations noted in the handwritten report, several major defects were identified on this Omega Speedmaster Triple Calendar calibre 7751.
Mechanical Wear and Damaged Components
- Advanced mechanical wear on multiple parts of the movement
- Damaged pushers requiring full replacement
- Worn crown tube causing loss of water resistance
- Oxidized or worn oscillating mass bearing
- Corroded bridges and screws compromising overall stability
Chronograph and Calendar Malfunctions
Several issues affected the chronograph, the triple calendar system, and the automatic winding mechanism:
Excessive play identified in:
- Automatic winding transmission
- Reverser
- Chronograph center wheel
- Pallet fork
- Escapement
- Balance bridge
Additional defects:
- Pallet fork replaced due to insufficient lock and short resting angles
- Hour wheel deformed, with three bent teeth
- Minute wheel incomplete, missing its specific 7751 washer
Lubrication Problems and Reduced Performance
- Power reserve measured at only 50 hours with chronograph engaged, indicating a weakened mainspring
- Oils completely dry throughout the calibre
- Excessive friction at the oscillating mass bearing
These flaws made a full overhaul indispensable.
Interventions Performed in Our Certified Workshop
✔ Replacement of Defective Components
The following parts were replaced:
- Pushers (new, sealed with Loctite + Araldite)
- Crown tube
- Oscillating weight (7750–7751 — old one rusted; new one incompatible with original screw → full replacement)
- Corroded bridges
- Complete pallet fork
- Bent and oxidized balance stop lever
- Hour wheel (3 bent teeth)
- Cannon pinion
- Minute wheel with specific 7751 pinion
- Additional screws (3 damaged screws replaced)
- Various automatic train and rotor components
➡️ All replaced parts are visible in the provided bag (photo included).
Mechanical Adjustments
Multiple adjustments were carried out to restore proper engagement:
- Reduced play in the automatic device → ratchet wheel
- Increased play at the reverser (lower bridge)
- Adjusted play on the chronograph center wheel
- Fine adjustments of the balance, pallet fork, escapement and plates
- Corrected barrel hole and bridge to eliminate excessive side-shake
- Deburred the oxidized horn tube
✔ Complete Ultrasonic Cleaning
All components were fully disassembled, cleaned, deoxidized, and inspected.
✔ Lubrication According to ETA 7751 Standards
Each lubrication point received the correct oil or grease.
✔ Final Adjustment and Testing
After reassembly:
- Chronograph fully functional
- Triple calendar (date–day–month) operates correctly
- Power reserve restored
- Stable and healthy amplitude
- Water resistance improved thanks to new pushers and crown tube
Probable Causes of the Issues Encountered
The defects likely resulted from:
- Natural wear of a complex movement requiring regular servicing
- Internal oxidation (pushers, tube, bridges)
- Impacts causing bent teeth and deformed parts
- Completely dry oils → friction + amplitude loss
- Abnormal rubbing of the oscillating mass
- Incorrect engagement in the escapement and pallet fork
The calibre 7751 is robust but demanding: without proper maintenance, internal damage develops quickly.
Final Result
After a full restoration, this Omega Speedmaster Automatic Triple Calendar now functions with:
- stable and reliable accuracy
- healthy amplitude
- a perfectly operating calendar
- a smooth, responsive chronograph
- a clean, lubricated, and precisely regulated movement
A crucial intervention for such a complex and refined calibre.
