Guest Sql_pl Posted January 6, 2009 Report Share Posted January 6, 2009 A friend of mine got really into reps. He bought around 7 pieces in last couple of weeks, all from Joshua and is amazed by quality etc. But one of the watches started to act weird. It is an a7750 powered watch and it runs, small sec hand rotates, chronograph works perfectly but main hour and minute hands (showing time) are dead. I can set them easily with crown but they just stay stopped when the crown is pushed in. Do you know what might have caused this or what might be the solution? Any help would be appreciated. Thanks Maciek Link to comment Share on other sites More sharing options...
Francisco Posted January 6, 2009 Report Share Posted January 6, 2009 One of the possible causes is the cannon pinion... there is no friction... Anyway...Just send it back... the watch is in guarantee. Francisco. Link to comment Share on other sites More sharing options...
RWG Technical Posted January 6, 2009 Report Share Posted January 6, 2009 Francisco is right. The cannon pin gear has no friction, no friction means no movement of the hour or minute hands. Common problem on the A7750, one of the many I fix when I do the servicing. RG Link to comment Share on other sites More sharing options...
Shundi Posted January 6, 2009 Report Share Posted January 6, 2009 Interesting...so you can still set the time and stuff if the cannon pin gear has no friction? Is setting the time controlled by a separate lever or gearing system or does it "catch" when you're setting from the crown? Pardon my ignorance but movements fascinate me... Link to comment Share on other sites More sharing options...
Guest Sql_pl Posted January 6, 2009 Report Share Posted January 6, 2009 Thanks guys! So new a7750 canon pinion will be needed. I wonder if it is easier to get a spare a7750 canon pinion to replace the one here or just ship it back to Josh. I assume eta 7750 cannon pinion won't work as I remember that a7750 designed hands do not work with gen 7750 as well... Link to comment Share on other sites More sharing options...
RWG Technical Posted January 7, 2009 Report Share Posted January 7, 2009 ETA cannon pins don't always fit on the A7750's for some reason, some do, many don't... The cannon pinion is the gear that separates the running part of the movement from the display part. Since the escape wheel effectively locks the movement as the balance swings, and lets out only one tooth each tic or toc, there would be no way to set the time, as those gears would be locked as well. The cannon pin/gear on any watch is the clutch between the going train and the display train, it allows the gears on top to move while the gears below keep running. When you move the crown to set the time, all the gears on the top of the movement turn, as does 1/2 of the cannon gear. You could only move the gears below if the pallet fork was removed. RG Link to comment Share on other sites More sharing options...
Shundi Posted January 8, 2009 Report Share Posted January 8, 2009 ETA cannon pins don't always fit on the A7750's for some reason, some do, many don't... The cannon pinion is the gear that separates the running part of the movement from the display part. Since the escape wheel effectively locks the movement as the balance swings, and lets out only one tooth each tic or toc, there would be no way to set the time, as those gears would be locked as well. The cannon pin/gear on any watch is the clutch between the going train and the display train, it allows the gears on top to move while the gears below keep running. When you move the crown to set the time, all the gears on the top of the movement turn, as does 1/2 of the cannon gear. You could only move the gears below if the pallet fork was removed. RG Ah I see that makes sense now that I think about it... thanks for the clear and prompt explanation The Zigmeister! Link to comment Share on other sites More sharing options...
Toadtorrent Posted January 8, 2009 Report Share Posted January 8, 2009 ETA cannon pins don't always fit on the A7750's for some reason, some do, many don't... Is this an issue because of the many variances of A7750s you have come across, manufacturing QC variances affecting fit, or micro-variances on the ETA parts themselves?? I guess the real question is, is this something you have to sort through a batch of gen ETA cannon pins and hope you find one that fits (making the cost of the pins high because of the failure of fit)... ...or is this a scenario where if you get a movement where one doesn't fit you have to do something to the movement itself? Link to comment Share on other sites More sharing options...
RWG Technical Posted January 8, 2009 Report Share Posted January 8, 2009 Is this an issue because of the many variances of A7750s you have come across, manufacturing QC variances affecting fit, or micro-variances on the ETA parts themselves?? I guess the real question is, is this something you have to sort through a batch of gen ETA cannon pins and hope you find one that fits (making the cost of the pins high because of the failure of fit)... ...or is this a scenario where if you get a movement where one doesn't fit you have to do something to the movement itself? Since this has been a common problem on the A7750, I have devised a fix for the original cannon gear. If the gear is beyond repair, I do have spare A7750 ones I can use, or in some cases I will install a ETA one. The common problem seems to always be the post on the great wheel that the cannon gear presses onto, it's usually slightly too small, and the gear slips on the post. I would say the ETA parts tolearance are correct, the variance is the A7750 parts. RG Link to comment Share on other sites More sharing options...
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