I recently acquired a Seamaster 166.032 Cal 750 or 752 (not sure) from my retired father as he doesn't wear a watch any more. I have noticed while wearing it that the second hand seems to skip and jump occasionally. Sometimes ill even see it stop for a second and jump to catch up. I'm not sure how often this happens as it is keeping perfect time. It seems that I can almost make it skip by rolling my wrist quickly. My dad cant pinpoint exactly how long its been since it was serviced but he figures about 6 to 7 years. It has been dormant for about 4 of those years until I asked to have it. Also in my research of the watch I learned that it can wind with the crown. My father never did this, he would just swing it lightly for a minute or so and than set it. The crown appears to be working perfect as I no trouble setting the time or date when it stops. However if I try to spin the crown away from me to wind it in as I have read, it wont turn even a 1/4 of the way. I'm not really sure what to do as this is my first automatic watch and as I said it keeps great time and easily lasts on the mantle overnight.

Sorry for the long post, any advice is greatly appreciated.

 

Hey Keys,

Pics are always appreciated, especially on an hierloom.

As for the issue, sounds like the watch is due for a service. I'd imagine a competent watchmaker could sort you out. The 75x is a good little movement and should be able to be returned to full function.

Cheers,

 

The movement uses an indirectly driven sweep seconds pinion, and this design can be a bit jumpy if the friction spring is not adjusted properly or is damaged.

This is a simple adjustment for any competent watchmaker to make, but only if the watch has had a fairly recent service. If it hasn't been serviced in several years, it's probably worth getting that done, and the friction spring will be addressed as part of that service.

Cheers, Al

 

Mine says hi

 

Thank you all for the responses, I currently live in Kentucky is there anyone or any place that you can recommend for me to take it or send it to for service? I looked up the omega site and $700 is quite steep. Any advice on why I cant wind it with the crown?

 

You say that when you try to wind the watch manually, "the crown won't turn 1/4 of the way"! Two possibilities. You are too timid when trying to turn the crown, OR there is actually something wrong. The crown on an automatic wind watch that is fully wound from having been worn will be harder to turn than the crown on an automatic wind watch that is totally run down. And some Omega crowns aren't "knurled" the way most generic replacement crowns are, thereby being a bit harder to grip. Off hand, I am unable to discern a possible cause for a crown that will only turn 1/4 of a turn, then seize. But if you are really concerned, maybe have it checked by a watchmaker.

 

Canuck after reading your post I put some effort into turning the crown and it does indeed turn with a little more force than I would have thought necessary. However it seems to make a small grinding sound that I can feel in my fingers through the crown. Is this normal? By knurled I assume you mean all the grooves in the crown which would make it easier to hold on to. If so, the crown is knurled.

 

I suspect the "grinding" you think you are hearing is actually the "whirring" of the reverser gear. You are also listening to the click on the ratchet wheel. This reverser gear accomplishes the winding of the watch regardless of which way the rotor is turning. If you have been wearing the watch, there is a chance it is fully wound when you wind it manually. That makes a difference as to how hard the crown would be to turn during manual winding. It is hard to speak with absolute authority as to whether there is actually something wrong with your watch without having had the chance to evaluate it. If you are still in doubt, have it looked at.

 

Hi @Archer, can you tell me if I well understand the concept of indirectly driver sweep second:
Indirectly driven means the second hand does not have his own pinion, but use friction with other hands pinion, which means it can « jump » or at least not be perfectly regular?
While a directly driven sweep second would have his own pinion, directly driven by the movement of the watch?

am i well understanding?
Thanks for your help!
(Ps: yes, I’m in a « second hand » period due to may last servicing, so I’m trying to educate myself on how does it works )

 

The indirectly driven sweep (center) seconds started out as a modification to the traditional configuration of the sub-seconds dial. Here is an example of how earlier watches were done:



There is a large wheel on the upper right side of the movement, above the wheel train bridge. It has been pressed onto an extended post of the third wheel. This large driving wheel drives the sweep seconds pinion that is in the middle of the movement - can't really see that as it's covered by a bridge.

In your watch, the configuration is the same as the 550 and 560 calibers. Here's a 565 - you can see that the sweep seconds pinion is located at the red arrow. It goes through the center wheel of the movement:



It is also driven by the third wheel of the movement, but the layout has been changed such that they don't press on a separate wheel on these movement. This sweep seconds pinion just drops in - as you see it there it is just sitting loose. The only other thing added is a friction spring, so here is a photo with that installed:



The spring is what takes up the backlash between the teeth of the third wheel and the sweep seconds pinion, while the watch is running. This prevents the hand from running in a jittery fashion as it moves around the dial. The first photo I showed has a spring also, but it's under that bridge.

So in all the various indirect systems, the seconds pinion is a separate part, and isn't a part of the main wheel train. This means that the movement can run without it installed.

Here's an ETA 2824-2:



This is a directly driven sweep seconds movement. This means that the post that the seconds hand is installed on, is part of the wheel train. Here's a photo with the bridges removed:



The seconds wheel is right in the middle of the movement. Unlike an indirectly driven sweep seconds, you can't remove this wheel and still have the movement work. It actually drives the escape wheel, so if you take this wheel out, the movement is not functional. There is no friction spring as there is on the indirectly driven designs.

Hope this helps.

Cheers, Al

 

Thanks @Archer it helps a lot!

If I’m understanding well, if the spring on the pinion is not tight enough, the second hand may skip some ticking or jump some second, so then the watch may lose some second, even if the mouvement is regulated to gain few second a day?

 

It won't "lose" time because the teeth do not disengage from each other, but the display of timekeeping will be erratic.

 

The only thing I don’t get is, what make the pinion of the second hand catch up when skipping a ticking... because in my mind it would lead to loosing as many seconds a day as it skips due to the lack of friction, but I guess I’m missing a point. Anyway, thanks again for your help

 

There's slack in that train. The friction arm is supposed to keep constant tension but sometimes it can't. That means the second hand jumps ahead until the slack is taken up and then whenever friction is lost, the second hand will jump ahead again. As Al said, the gears are always engaged, so all you're seeing is the slack in that train.

You can illustrate this to yourself by making a three-gear train with LEGO, hold one end steady and note that you can wiggle the other end quite a bit because of clearances.

 

Well, my mistake... I though that the second hand was only moving by friction on the jewel, I did not understand well!
Thanks for your help, i try to figure out how the watch run, not an easy task

 

Here's the sweep seconds pinion under the friction spring, and the third wheel driving it. Note the gap at the arrows - this is the backlash in the gear teeth:



The hand is always being driven in one direction when the watch is running normally. so unless something causes the hand to be forced the other way, it will stay meshed with no play. If the spring is not tight enough for example, the weight of the hand may come into play. If a watch has this problem, with the watch is positioned with the dial vertical and the 12 at the top, often if the hand is going "uphill" (the hand is going from 6 up to the 12) the weight of the hand will keep the sweep seconds pinion engaged and it runs fine. But when the hand is going downhill (from 12 back to the 6) the weight of the hand may cause the hand to fall slightly due to the backlash, the teeth of the third wheel stop driving, the hand stops momentarily, until the teeth of the third wheel "catch up" and starting driving it gain.

But all this time, the watch is ticking along normally, and when the teeth catch up the time will be where it should be. So perhaps if you happen to measure the time precisely when one of these stutters happens, you might not get the exact timing by a few seconds, but again this is just an issue with the way the time is displayed by the hand, not the timing of the watch itself.

I'm sure if you give this some serious thought, it will be pretty obvious.

Cheers, Al

 

@Archer now that’s crystal clear! Your pictures are amazing and helps a lot, thanks a lot for that.

In my mind, one dent of the wheel was 1 ticking, but I know understand (hope I’m right) that it is a more continuous mouvement of wheel and pinion that leads to the sweep second

 

@Archer when my watchmaker was finishing up my KO 2627 with cal 355, he remarked on the friction spring needing tuning. My response was to buy a new one. Life's too short sometimes to fine-tune those things.

 

Even new ones often need fine tuning. It only takes a few seconds to adjust, so would take more time for me to sit down and order one...

 

My sense was that it was worn out; this watchmaker is a pretty talented young guy, and if he was having issues with it, screw it, get a new one.

He is reluctant to spend other people's money, which is one of the good things about him.