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Starting Chrono Stops the Balance on ETA 7750 Clone


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After removing/replacing the auto-wind module (for cleaning) on an ETA 7750 clone in my Daytona, the balance (watch) stops as soon as I start the chrono.

 

The oscillating pinion IS running when the chrono is OFF & it DOES move into contact with the center (chrono) 30-minute counting wheel (center wheel that drives the chrono seconds hand) when the chrono start pusher is pressed. So I know that much is working. The problem is that as soon as the (running) oscillating pinion comes into contact with the 30-minute counting wheel, the balance stops. If I press the chrono start pusher again (to stop the chrono (which moves the oscillating pinion AWAY from the 30-minute counting wheel), the balance starts right up. But if I restart the chrono, the balance stops. I cannot figure out why the oscillating pinion is stopping the balance?? Can any of you watchsmiths spot the problem?

 

I am in process of relocating & have alot of clutter all over & space is very limited my workspace, so I do not want to do a full disassembly (too much risk of parts getting lost). Since the chrono was working fine prior to my r&r'ing the auto-wind module, I think I must have disturbed something related to the chrono that is directly beneath the auto-wind module. I have had the automatic device bridge off at least a dozen times looking for a chrono pinion, clutch, wheel or hammer that is not properly installed &/or aligning with a jewel in the bridge, but everything appears correct.

oscillating pinion.jpg

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  • 3 weeks later...

Question -- How to affix a wheel to a pinion that is too small for the hole in the wheel?



Background -- After being unable to figure out the cause of the locked pusher, I just ended up doing a complete overhaul. During disassembly, I found the pinion of the chrono minute wheel was broken, but I cannot see how that would cause the pusher to get locked?

 

I also found the wheel referenced above that was supposed to be press-fit onto that chrono minute wheel pinion had the broken bit of that pinion stuck in it. Fortunately, I was able to get the broken pinion piece out of the wheel without damaging it. I ordered a new ETA chrono minute wheel.

 

Anyway, it turned out that the clone's chrono minute wheel pinion is about twice the diameter of the pinion of the gen ETA part. This I did not realize when I installed the new ETA minute wheel & reassembled the movement. So, now, the hole in the wheel that is supposed to be press-fit onto that ETA chrono minute wheel pinion is too large, so the (press-fit) wheel is just spinning free & unable to move the chrono minute hand on the dial.

I tried staking the hole smaller, but my smallest concave staking bit only partially closed the hole, so it keeps sliding down the pinion & out of position to mesh with the adjacent wheel.

 

The pics below show the wheel that WAS press-fit onto the chrono minute wheel (which is located on the other side of the movement) & a comparison of the diameter of the clone chrono minute wheel's pinion (thicker) to that of the ETA chrono minute wheel (which is installed in the movement).

I was thinking of dabbing a bit of epoxy onto the top of the wheel which I think might work, but I am worried it might migrate down below the wheel & cement it in place. Or, worse, it might migrate into the movement & kill the entire thing.

Any of you watchmakers know of a safe & effective way to lock that wheel (circled in the 1st pic) onto that pinion (sticking up through the wheel)?

Hour wheel pinion & driving wheel 2.jpg

Hour wheel pinion & driving wheel.jpg

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