New to the forum, opening request for assistance on cal 751

Greetings all, I'm very new to the forum, and delighted with the amount of solid information that's been built up by passionate collectors and officiandos. I'm particularly interested in vintage Seamasters, and have a question for those far more experienced than myself.

I have a 1968 Seamaster dual date chrono with cal 751 movement, keeping good time between -10/+4 depending on wearing angle, good amplitude >200, and the date plunger is working very well. The problem, or perhaps issue, I'm experiencing is the calendar day advances intuitively around the midnight mark, but the calendar date doesn't advance until 6:30am or so. I'd like to know if there's a subtle operation I can do with the crown to get the day and date to advance reasonably close to one another, instead of the 6 hour offset I'm seeing now. Or is this just something I'll need to live with until its next service? Could this problem degrade further as I let the watch wind all the way down from time to time?

Fortunately I don't really check the date until 9am or so when the work day is in full swing, but it does drive me a little crazy anyway. I just took this photo while writing this, so THU is in the middle of advancing to FRI - 16 will advance to 17 at about 6:30am.


Thanks everyone for reading!

Nice sparkle dial Seamaster chrono. I think this is one of those things that needs to be done by a watchmaker. What's it's service history (I'm secretly betting you don't know at which point I can sagely recommend a service now anyway)?

I hate to do this, but there is a detailed answer on WUS
http://forums.watchuseek.com/f20/da...al-914102.html#/forumsite/20758/topics/914102

Thanks to both of you, sound advice on both fronts. Service history is unknown, but I did have my watchmaker have a quick look when I picked it up to test regulation and amplitude. I didn't point out calendar issue at the time, and now that I know what's going on, I'll sit on it until the next service. I've spent my service budget for the next while on a couple of other watches.

Very, very occasionally! 😎

Thanks for the awesome info! Do you see this calendar drift issue as a chronic issue on the 751's? Is there something I can do to help prevent it from happening, or at least minimize it?

Thanks again everyone who's replied to this thread!

I haven't owned the watch long enough to observe drifting effect, perhaps I used an inaccurate term. From what you're saying, I would interpret that the existing behaviour of the date rolling over at 6:30am is an artifact of a previous service, whereby the watchmaker assembled the movement back without adjusting the date function carefully.

Service history is unknown. My watchmaker's bulk of business is with vintage Omega, and I trust his opinion - though I have not scrutinized his setup, I have faith that his instrumentation was well aligned with this movement. His comment was "amplitude is well above 200", I did not ask about the state of wind at the time, again trusting his expert opinion.

In the end though, you have settled my nerves about the state of affairs with the date function. I was primarily concerned that I may have been incurring additional wear by letting the watch run out of optimal adjustment.

On the one I serviced, the day change operation takes two hours to complete its operation. I set mine to complete both the day and date to finish changing at midnight.