Adjustment of screw(s) on cal.285

It may be the resolution of the photo, but if you zoom in on the chronograph runner there appear to be several areas with worn/damaged teeth.

enjoying following along with this thread!

I think that once I realised what that shouldered screw does and I tightened it properly, as you say, this problem became much easier! It is all in the adjustment of ES-2 (a) so that when I press the button, the gap at c disappears and the small wheel starts driving the centre wheel. [I don't think there is wear on any teeth]

Which it basically did. But ES-2 is quite difficult to turn and only needed a quarter of a turn before the wheels started engaging and everything started to work! And no hunting!

The only problem I now have is that in order to engage properly, (notice how I bandy that word around as if I know what it means) I think it needs a sixteenth of a turn more, - and either I need to sharpen the screwdriver, or I cant get ES-2 to turn any further.

Keep trying? Or am I at the end of the travel and s there a coarse and fine adjustment

I think I may have identified at least something.

Should the driving wheel bridge connecting the ES1 screw (including that lollipop shaped piece) with the crown wheel be extremely loose? If I barely touch it, the driving wheel starts touching the centre wheel.

There is no play to the driving wheel but is there adjustment to the spring just to the left of and below the ES1 screw?

You seem to have a lot of issues and, I would send it back as you run the risk of damaging something.

I'll call the piece outlined in red, "the coupling yoke". It pivots about ES-1 and the spring outlined in green is always trying to push the coupling yoke so that the little wheel contacts the central chronograph runner.


When the chronograph is in the off position, the coupling yoke can't move across because the "prong" on the end of it contacts one of the pillars. From your picture and circled in green. Note that the coupling yoke is not touching ES-2, which is correct.


When you start the chronograph, the "prong" on the coupling yoke drops into one of the gaps between the pillars as the pillar wheel has turned half a tooth around. You can see that in my picture above and you can also see that the coupling yoke is touching ES-2.

The only thing that stops the green spring pushing the coupling yoke over until the "prong" bottoms in the gap between the pillars is ES-2. You adjust that so that the coupling yoke can't move further than you want for the correct depthing to the chronograph central seconds runner.

The spring doesn't have any simple adjustment and, you should not be able to push the coupling yoke towards the centre of the movement as it is stopped by ES-2 and the spring should have pushed it over to ES-2. In the first picture you showed, the spring looks to be engaged, has that been disturbed? It does sound like it needs a more in depth analysis and everything should be checked. Even if you resolve this, would you be happy that there are no other issues?

Best regards, Chris

Everything seems to me to be working correctly except for that spring. Even the most minuscule touch to that spring gets the seconds wheel moving.

The clutch coupling is not fixed. It should be free to move. It pivots on es1. The is a spring (circled with numbers 1 and 2) that pushes clutch coupling (and driving wheel) towards the second runner or second wheel. It could be that the eccentric is damaged or the spring is either not fitted correctly or damaged (does not exert enough tension of clutch coupling). The spring is held down by a screw. It also has a guide which aligns the spring correctly so it exerts pressure on the coupling (8080) ...

Yes, that's exactly what I had identified, though I call it a spring and you point out that it is a clutch coupling. It doesn't seem to exert enough pressure on the yolk under the ES-1 screw. It doesnt seem to adjust. How is it tightened? Is there some procedure for bending it a bit so that it exerts more pressure where it touches? Or is it not possible to bend it a bit because the pressure IS correct and that lack of pressure is indicative of some other problem?

You can see that the coupling yoke is not touching ES-2 in this view even though it should be as the prong is between the pillars (see my comment above). If it did, the depthing (gear engagement) with the central chronograph runner would be far too great as ES-2 has been adjusted too far. You should adjust ES-2 now until it is almost touching the coupling yoke in this view or you risk damage to the gear teeth when it eventually swings over:


This is what the spring looks like on the underside.


You can see a little dowel there that goes into a hole in the plate and then a screw is placed through the hole in the spring - this means its position is fixed. It has a little lip over the top of the coupling yoke and looks to be correctly fitted in your picture.

You're saying that the coupling yoke is completely free and you can just nudge it over with no effort? If that is the case, then the spring is not exerting sufficient force and you need a new 285 part #2580 (you should check the part number but that's the only similar spring i see in the parts list). The thing is that springs don't suddenly lose their stiffness and I am concerned that there is some other issue. Remember the black arrowed shouldered screw? With that completely loose, does the coupling yoke swing over under the spring pressure? If so, that may be the wrong screw and the shoulder is insufficient for the yoke to move in. There are other shouldered screws in this calibre and it may be mixed up... Or it may be that ES-1 is damaged and the coupling yoke is not swinging because it is stiff in that eccentric.

It is getting complicated so, ff the watchmaker you're using is still willing to take it back, I'd send it to them.

Cheers, Chris

I have to agree with on that ...

Ye, if the ES-2 yoke is supposed to be touching the eccentric screw, I really must have messed something up. (Whether or not I can easily get the seconds hand to start by touching the coupling clutch)

They are nowhere near each other. And the yoke is exceptionally loose for some reason I cant see.