Patek Philippe - 240 Q movement question

240 Q movement question

Jan 12, 2020,12:07 PM

I bought a 3940 (2006 vintage) in November, and I'm having an accuracy issue that is more interesting than it is troubling. The watch is accurate over the long term (say, after a month) and never more than a minute off. But if I check it in any given moment, the minutes hand is often a minute or fast slow... then corrects over the next few hours. Sometimes if the minutes hand is a minute slow, I have seen it *speed up* to catch up with the true time. Sometimes if it is a minute fast, I have seen it *stop* for a minute, as though to let the time catch up with it. Also, the deviations cannot be truly random, or else they would not completely cancel out over the long term; the watch would become (for example) five minutes fast or slow over a few weeks, not always within a minute of the true time.

This is not a typical accuracy problem. My hypothesis is that the movement itself is spot on, but that there's "play in the joints" between it and the minutes hand, which is thus free to wander forward or back -- but only with a tolerance of one minute of the true time, which the movement accurately tracks. Btw, the watch is not magnetized, and it is always fully wound because I wear it every day. Has anyone else had this issue? Again, I'm not troubled so much as I am interested in what's going on.

(Btw, apologies to those of you who saw this post earlier with only the opening sentence; there's an issue with the "edit" function in the app, which deleted my entire entry except for the first sentence when I tried to fix a typo.)

Yes.

By: baufoam : January 12th, 2020-13:16

I wore a 3940 nearly every day for about 10 years. It behaves in exactly the way that you are describing. It speeds up and slows down but ends up back on time or very close to it. My 3940 is probably accurate to within about 3 minutes per month. I have ha...

thanks --

By: Chromatic Fugue : January 12th, 2020-17:33

happy to hear mine is not the only one. The variation here is not a problem for me as long as it stays within its current bounds.

3min per month is

By: Rapwatch : January 22nd, 2020-12:40

Pretty average to poor. Especially if you are cogniscent enough of your positional performance to rest overnight in suitable position to gain or lose against real time. You should achieve close to 0 PPs are supposed to run -3 2 s/d according to their own ...

Thanks, but

By: Chromatic Fugue : January 22nd, 2020-13:34

I now realize, for the reasons discussed here, that problem isn’t with the movement. The problem is with the play in the joints between the movement and the minute hand. Because of the nature of the issue, the minute hand can “gain” or “lose” a minute a d...

A quite common problem is to little friction in the minute tube.

By: xyz123abc : January 12th, 2020-13:27

Can be fixed, but it requires some skills and experience (and a dismantling of the movement). So your theory is most likely correct.

thanks for the insight!

By: Chromatic Fugue : January 12th, 2020-17:34

I'm OK with the status quo and in no hurry to have anyone open the case, so I think I'll do nothing until the next service interval.

Such a high fluctuation is very poor. You may have a bent pivot

By: Rapwatch : January 22nd, 2020-12:33

I suggest you attend to it soon.

Thank you for the explanation.

By: W72 : January 12th, 2020-22:00

I also have several watches, including a 240 PP movement exhibiting the same. In addition to the friction in the minute tube, can it also be attributed to the placement of the dial. Ideally, the dial centre is also the exact centre of the hour/minute hand...