Valjoux 72 sliding gear adjustment

[watchfellow]

Hi everyone,

I have a Valjoux 72 where I can't seem to adjust the sliding gear properly. If I bring it too close to the chronograph runner, the runner hits the gear twice in one turn (as shown in the photos). I have tried to adjust the eccentric screw slightly but as soon as I bring it a little further away then the runner doesn't hit the gear at all. To complicate matters the runner and gear don't seem to hit each other consistently at the same angle, almost as if the gear moves around. I checked the sliding gear spring however and it seems tight and doing its job.  Any suggestions?

[nickelsilver]

The wheel on the sliding gear should have a tooth pointing directly at the center of the chrono runner when the chrono is engaged. As it is you have a tooth space pointing at the center. To adjust this you move the minute counter jumper, most later 72s have an eccentric for this adjustment. Then you adjust the depth of the sliding gear so that the finger on the chrono runner engages the tooth pointing at it, jumps the minute counter, then it can just touch the following tooth but shouldn't engage it enough to lift the minute counter on its jumper.

 

It can be a bit of a balancing act to adjust, as when you adjust the depth of the sliding gear its wheel is turning around the minute counter wheel, changing its position (how the tooth is pointing at the chrono runner). You might have to go back and forth a little bit. Also, depending on how the eccentric for the minute jumper is positioned you can increase or decrease the tension on the jumper enough to either not have enough tension to jump, or so much it stops the watch; this is adjusted by bending the jumper spring.

 

Finally check that with the hammer engaged, it's making full contact with the chrono runner cam, and there is a little play at the minute counter cam, but not enough that a tooth can go over the jumper in either direction.

[HSL]

I assume you been turning on the ES – 3. This excentre Is used to adjust the depthing of the intermediate wheel with the seconds wheel tooth dart. When gently moving this in different directions will adjust the depth the intermediate wheel will go into the minute wheel and the depth of the seconds tooth dart.

This has to be adjusted to perfection, usually the ratio of the depth is the intermediate wheel tooth goes in 2/3 of the depth. This is sometimes hard to see so the most puts it in ½ of the depth or just below.

The seconds wheel tooth dart when att correct depth it just touches the intermediate wheel.

One really don’t turn these excentres once they been put in the correct position. You for sure don’t try to lift them of since then you remove the wax they have been locked into position with, they then will just freely rotate around in the hole.

If your minute hand moves in an erratic way the culprit most of the times are the minute wheel jumper. It might not be correctly aligned in the middle of the teeth or it is not there at all.

Hope this might help-

.