Omega Speedmaster - loses ~30 seconds on time set

[jimboski93]

I have an Omega Speedmaster chronograph (ref 324.33.38.40.06.001) that I've had for a bit more than 10 years.  It has the Omega 3304 / ETA 7750 movement.

I'm not sure I'd ever paid close enough attention to this, but here's the problem I'm having:

I set the time against time.gov to align the seconds at :00 and the minute hand pointing exactly at the minute.  If I watch closely, the minute hand doesn't move for ~30 seconds (and almost looks like it moves backwards for ~15 seconds very faintly, then starts to move forward).

I've tried setting the time when the seconds are at :15 or :30 or :45 as the minute track has marks in between each minute at this point, but I get the same result -- the seconds will remain tracking time well, but the minute hand won't be synched up (i.e., when the second reach :00, the minute hand is halfway through the minute).

 

The solution for me has been to set the minute hand to be 30 seconds ahead, then everything will synch up.  (For example, set minutes to reflect 9:22:30 when the time is actually 9:22:00 and press in the crown.  By 9:23:00 the second hand will be pointing to :00 and the minute hand will be pointing to 9:23:00 and everything will be synched up).

But my question here is really:  am I crazy?  How can a minute hand not move for ~30 seconds when the crown is pushed in?  If there was something critically wrong with the watch, I'd assume I'd be losing 30 seconds each minute, but this only happens when I set the time.

[mbwatch]

Hi there. Your 7750 may be experiencing an issue with its friction driving mechanism. Mechanical watches have a connection between the balance and train of wheels on the back of the movement to the motion works on the dial side of the movement, in the form of a pinion or wheel that slips like a clutch when setting the hands, but grabs with friction and should not slip when the watch is running.

As that part wears, it may lose sufficient friction and that has the effect of the minute and hour hand losing time even though the watch may be running normally otherwise. Sometimes it is extreme, like losing 15-20 minutes suddenly but it can also be just seconds before the minute hand "catches" and begins to turn. The 7750 has a driving wheel that should supply friction (this part in this disassembly video) and it may need to be replaced or tightened. Do you also notice that it feels easier or a little sloppy to set the time than before, like the hand setting moves too freely?

In any case, if you've been using this watch for 10 years it is time to have it serviced by a professional watchmaker. When you take it in, make a note that it seems to lose a little time immediately after setting.

[nevenbekriev]

I am not the one to say if You are crazy, but what You describe is common for the movements with indirect driving of minute hand pinion and 7750 is one of them. The simple explanation is that there is a free play between teeth of wheel that drive the pinion and the pinion leaves (the mesh between wheels) and this free play measured by the hand moving is about 30 sec. This is due to the construction of the movement and is fully normal. To avoid what You describe, set the time finally by moving the hand back, not forward. Wat I mean is if You need to set 12:00, then set to 12:01 and carefully turn back to :00, thus the hand will start moving immediately after pushing the crown in.