7733 chrono engagement problem

[watchfellow]

Hi everyone, I have a Valjoux 7733 that I cleaned and assembled, but am having trouble with the chrono engagement. I don't have a problem moving the hammer manually and switching the chrono function on/off, however when I placed the movement inside the case I found that the pusher won't engage the chronograph. The operating lever slides as it should but it doesn't seem capable of moving the hammer to engage the chrono. It can however turn the chrono off if I first engage it manually with the hammer, but again it won't move the hammer to the on position whether from the stop or reset position (the reset function works fine). I'm not sure if the issue is with the operating lever? I replaced it thinking that was it, but it still won't work.

Hoping someone might have an idea of where to look. I've attached two photos, one with the chrono on, one with it off.

[nickelsilver]

The mechanism looks OK, this could be as simple as a lubrication issue. The jumper for the cam (hammer) and the finger of the operating lever and the faces it touches really need to be greased. If they are dry there's a good chance it just won't work.

[rodabod]

While it's cased, can you engage the chronograph by pressing the operating lever where the pusher actually presses against it? Just trying to rule out the pusher action itself.

[rodabod]

Also, you have not installed the movement tabs in the photo which secure the movement to the ring. Lateral play can affect the action.

[watchfellow]

Thank you nickelsilver and rodabod for your help.

I re-lubricated the hammer and the operating lever again just in case, as well as tried working the chrono after locking in the movement with the case back, but still no luck. 

On closer observation, I can see that the operating lever just doesn't have enough movement to push on the tabs of the hammer. It only seems to have enough "length" to hit the tab when the chrono is in the on position and it needs the least amount of length to travel. Once the hammer/chrono is in the off position or reset position, the arm of the operating lever just doesn't reach enough to hit the hammer tabs. 

It's also definitely not the pusher, as the lever travels the same distance if I engage it manually. I took a photo of it activated, without the hammer attached. Anyone have an idea if the length of travel looks correct?

I also took a photo of both the original hammer (underneath so the tabs are visible) and the one that I replaced it with, thinking maybe the issue lies with them. Interestingly, they seems to be a little bit different from each other!

[Delgetti]

Are you sure the operating lever is assembled correctly?

From my point of view it lies quite too much to the center of the movement.

 

Please have a look at my 7734 walkthrough to the pictures 19, 20 and 21.

The layering of the lever is tricky, there is a part of the bridge lying between two parts of the lever.

 

 

[watchfellow]

On 8/7/2021 at 4:21 AM, Delgetti said:

Are you sure the operating lever is assembled correctly?

From my point of view it lies quite too much to the center of the movement.

 

Please have a look at my 7734 walkthrough to the pictures 19, 20 and 21.

The layering of the lever is tricky, there is a part of the bridge lying between two parts of the lever.

 

 

Thank you Delgetti, that's exactly what it was. The lever was not assembled correctly. I re-assembled it and it clicked into place and now works correctly.