Chrono hour counter problem on Omega

[johnmacky]

Hello Mark, hello folks,

My first time post here and I hope you can help with my small issue, I have an Omega day/date with 1151 movement. It is working perfectly in general, until I noticed something is out of order with the chrono hour counter, the subdial at 6 o'clock. If I stop and reset the chrono to zero, it looks fine, but that small  hour hand seems to keep on turning, although very very slowly, for example, in the picture here, you can see it moved  30 degrees in about 48 hours, now pointing to 1. I was wondering what might be the problem here and if this is a small fix that can be performed by a regular watchmaker, as I don't want to send it to Omega for their pricey "full service" which they always try to convince you is needed.

Thank you.

 

[wls1971]

With the chronograph stopped, if you press reset does the hour hand jump back to zero, I only ask as it could be something as simple as the hand is lose on the pivot.

[johnmacky]

Hi wls1971,

You know, the hand being loose was my first thought but it seemed to be advancing kind of regularly.

I just pressed reset and it went back to 0 (12).

 

 

 

[clockboy]

It could be as suggested a loose fitting hand. However it will need looking at by a qualified watch repairer. Chronographs are more complex than a normal watch so require a lot of time to strip inspect & repair. If it is the hand maybe a easy repair but I have my doubts.  

[wls1971]

Apparently this is know as "hour hand creep", and is a know problem with the 7750 based Omega chronographs

This is a explenation from the chronomaddoxx site

http://chronomaddox.com/tzof_faq.html#Chrono_Hour_creep

[sstakoff]

Have a  look at this video. At time 2:20, Mark assembles the hour counting wheel mechanism. The way the hour counting works on this watch is that the wheel is attached directly to the mainspring barrel via a clutch mechanism. When you reset to zero, the hour hammer spins the wheel back to zero and the plastic lock engages the edge of the wheel, preventing it from turning - and activating the clutch. I suspect that plastic part is worn. All in, it's a simple repair, but it must be done by someone that knows what they are doing!

 

[sstakoff]

5 minutes ago, wls1971 said:

Apparently this is know as "hour hand creep", and is a know problem with the 7750 based Omega chronographs

This is a explenation from the chronomaddoxx site

http://chronomaddox.com/tzof_faq.html#Chrono_Hour_creep

Also a very plausible explanation. Once the hour hammer resets the wheel, the hammer spring (which Mark is shown fitting)  is what keeps the tension of the hour counter lock (plastic part) against the hour counter wheel. If this spring tension is off, it would have the result previously described. Too bad they use plastic for this part. I suspect they do so to minimize the wear on the counting wheel itself.

[johnmacky]

Thank you guys, these were the answers I was looking for, I watched that video yesterday but didn't know what exactly I should be looking at.

 

 

 

 

 

 

[SSTEEL]

The hour brake is only plastic, and often wears, so replace this for new, and your good to go.

[johnmacky]

59 minutes ago, SSTEEL said:

The hour brake is only plastic, and often wears, so replace this for new, and your good to go.

Ah, if only "I" could do it

Just to know for myself, in Mark's video assembling the calendar, is this the plastic stopper we're talking about ?

 

[sstakoff]

11 minutes ago, johnmacky said:

Ah, if only "I" could do it

Just to know for myself, in Mark's video assembling the calendar, is this the plastic stopper we're talking about ?

 

That's it!

[clockboy]

So thats what it is for. When I service a 7750 I always did wonder what its purpose was.  If correct a very easy fix once the hands & dial are removed that is. 

[SSTEEL]

Yes thats the kidney, its mostly a plastic component, but on some other calibers it can be metal, seen these on some Omega's.

Edited March 15, 2017 by SSTEEL

[johnmacky]

Yep, I also learned that Omega has updated it in later versions of the movement, which they might install in case it's brought to them for service.

Anyway, it has been more than 36 hours since I last reset the chrono, and this time the hour hand has 'creeped' only very very little, perhaps half a millimeter, here is a pic of it, it might seem that it moved more than that, but the hand doesn't exactly reset right in the middle, but more like near the edge of the white dot, so apparently it  moves at its own whim :