7750 Test

[bjd1020]

I was wondering if anyone had a formal process to test a 7750 before tearing down.  I have a friends watch here an he says its not running properly, he thinks the main spring is broken as the watch doesn't hold the power reserve it used to.  I have let the watch power all the way down.  Before tearing the watch down I was wondering if there is a recommended procedure on evaluating the watch before putting it on the time machine.

AND BEFORE THAT GUY WHO SITS AN WAITS FOR QUESTIONS TO BE ASKED SO HE CAN REPLY...."USE THE SEARCH FUNCTION"  I HAVE ALREADY DONE THAT.

[Nucejoe]

Hi, Turn off all complications. Wear the watch for a day, bench test for power reserve, make a note of how long it runs.

If low power reserve, try winding manually through ratchet wheel, listen close for the sound of sudden power discharge.make a note of how long it ran.

If you gain access to the barrel, suppy power by pushing the barrel ( by hand or a polymer stick) reverse direction to observe how freely the power train responds.

If it came down to movement strip down. In addition to diagrams/datasheet take a snap shot at each stage of strip down, actual pictures come of use for  diagnostic help.

Mark ratchet wheel with majic marker, manual wind through rotor, observe winder mech, the fault may be in selfwinder mech and easily found. 

Post the results for discussion. Good luck

[Nucejoe]

Hi, , Referring to eternaltools.com to see ETA parts illustrated with names correspondingly. Helps common language. Surely you know ETA 7750 is no ordinary movement, if your first attempt, providing complications are avoided attack can be recommedable.

If the watch runs like 30 min on bench following a normal day on wrist.chances of faulty spring-barrell are high, weak or broken MS, or  MS may dislodge from barrel notch prematurely.  

If the watch runs like 8 hrs chances of weak or faulty winder is likely to be the issue.

Well video or photoed stripdown is of high importance.

Did you see" Assembly of a valjoux 7734" by delgetti?  

Regards joe