7750 chrono pusher doesn't engage cam

[sneed12]

I bought a beautiful TAG chrono from another member. When it arrived, the chrono was running and the start/stop button would not work.

I took the back off and after some digging I think I have diagnosed the problem. The little toothed part that engages the chrono cam doesn't engage it normally, and in fact I think it's installed backwards. If I push it into the correct position with a tweezers then it will engage the cam one time, but won't reset properly.

Here is a movie showing the problem. Before the movie start I pushed the piece into position then gave a bit of pressure with my finger on the pusher. When I push it the first time it engages the cam correctly and starts/stops the chrono, but when I push it again it is out of place and won't engage the cam.

http://diablo.phys.northwestern.edu/~devildog/a7750/IMG_0579.MOV

Looking at the parts diagrams from ETA it really looks to me like it's installed backwards/upside down, ie the side facing the caseback should be facing the dial. How hard is it to remove this piece? Can I just pull it off with a hands puller, and if so how would I reinstall it? If not, can I just remove the screw holding that lever down and pull the whole thing off? I'm hoping this is a fairly easy fix...

[14060 or 16610?]

From my RepGeek post:

I can't play the movie, my media player wouldn't recognize the .mov extension. I think I need iTunes or QuickTime to view it and don't have that on this PC.

Anyway, let me comment without seeing the movie. It appears you are pointing to the L-shaped lever. That lever has a hinge in it and actuates the heart-shaped chrono piece in 2 different positions to start and stop the chrono function. I don't think I've ever seen that piece installed backwards, and I don't think that's possible. What I have seen is misalignment of this piece and/or misalignment between it and the heart-shaped chrono piece.

You can remove the screw holding the piece on, and remove the piece with no problem, but then what? You can't install it any other way. Also, you may have trouble realigning the spring for the 30-minute actuator keeper.

[Bike Mike]

I know exactly what you are talking about as I have seen this on a couple watches that I recently serviced. One issues seems to be the piece that engages the cam can be too short on the Asian movements. The other issue I have seen is relative to the pivot points.

I just finished a Pam Ferrari a few weeks back because it would not run. The "fork" piece that engages the cam had busted off and lodged itself into the balances assembly. I replaced the 2-Funtion Lever with 3 different Asian spare levers I had from part. 2 of the levers did not work properly. Would engage the cam to start the chrono, but would not engage to stop the chrono. The 3rd lever worked, but barely and felt terrible. So I Installed a Swiss ETA 2-Function Lever (~$30) and the issue when away and the chronos started & stopped flawlessly. Worked much, much smoother then the Asia pieces too! Did some measurements and found some pretty big differences between the Asian and ETA pieces. The more I wok on these Asian movements, the more I find how superior the Swiss movements are.

I was going to do a write-up about this, but I have not had the time lately.

[jcrry2]

this happened to my topgun. it have yet to get it fixed. but it still runs fine the chrono just wont stop.

[14060 or 16610?]

Yes, there is no comparison obviously between the Swiss and Asian parts. But the fact that the piece was installed upside down completely baffles me. I hadn't seen one like that yet.

[Bike Mike]

I see what he is saying is installed backwards