GMT (1675) Two Technical Questions

[StanGMT]

Hi,

Are there any Rolex technicians out there who can advise me, please?

My GMT was recently serviced and you know what it's like - when you get your watch back from servicing you really examine it for defects or anything that needs attention. Although my watch seems to be working fine there are two things I've noticed that I don't know whether to send it back for attention:

1. As you will be aware, adjustment of the second hand is achieved by applying a gentle reverse pressure on the crown (when it is pulled-out to the hands-adjust position). This stops the second hand until the correct second-point is reached. Releasing the crown then allows the second hand to move again. What I am finding since servicing is that the usual gentle reverse pressure on the crown doesn't stop the second hand. It is really difficult to get it to stop at all and that is only after carefully 'teasing' the crown, virtually to the point of winding the hands backwards, in order to stop the second hand. Sometimes I do reach the point of reverse-winding the hands and the second still doesn't stop. Any idea what is going on here and what should I do about it?

2. The date change occurs at 2-3 minutes before midnight. Nothing much wrong with that, but I've just noticed that, at the instant the date 'clicks' over, the red 24 hour hand jumps very, very, slightly clockwise. It is as if the release of sprung energy that moves the date ring is somehow linked to the 24 hour hand movement (which seems logical). This movement of the 24 hour hand really is only very tiny and it might always have been there - it's just that I've only noticed it now following this service. My question here is: Is this slight movement of the 24 hour hand when the date changes normal, or is it some sign of old age with my watch, that I need to attend to?

Any information and/or advice on this would be much appreciated.

Stan.

[Dan Pierce]

Sorry Stan, I don't have any answers for ya'. But Mike will be along soon with all the info you'll need.

Questions though, who did the service? Any issues about the age of your GMT?

Thanks,
dP

[abigsecret]

Issue # 2 is not an issue at all....

#1 at the other hand, should be corrected I think. Looks like the balance stop spring is defective.

Good luck!

[mike]

Well, I guess this is one of the strange things about watches.

I have two 1675s,

My gilt dial can be hacked in the manner you describe-slight back pressure on the crown. The watch was serviced less than a year ago by Chicago (the Independent)

My white will not hack. It's circa 1968. This one was serviced one year ago by RSCNY.---go figure.

I've not noticed any movement in the 24 hr. hand. Date changes a couple minutes past 12 on both and both start running within 5 to 6 turns upon winding.

[StanGMT]

Thanks, folks.

Dan - The recent service was done by the technician I have used for the previous three services (that must be about 15 years). I've never had any problems with him. He's Rolex approved and his updated certificate from Rolex is hanging on the wall of his workshop, so I reckon he's probably sound. As for age, there are no age-related issues that I'm aware of, only that I'm a bit slower these days!

Regarding your comments, Mike, my watch has always hacked nicely - it's only following this service that I've had a problem. Come to think of it, the watch was working perfectly right up to the service, so it probably is NOT an age issue.

Mireyna - can you expand on your comment that #2 isn't an issue, please? Are you saying that this 'twitching' of the 24 hour hand when the date clicks over is common? Is it that you would expect the mechanical arrangement of the 1675 movement to produce this effect?

Thanks again,
Stan.

[Tools]

Stan,

I would take what Miyrena says to the bank..

If you are concerned with the non-stopping ability, armed with Miyrenas comment, take the watch back to your watchmaker and ask about replacement of the balance stop spring..

As far as your hand twitching, there is quite a bit of action going on at date change.

Here is a pic of a 3135 date wheel. Behind it is a spring loaded lever that, at midnight, slips into a detent releasing the spring and lever to engage the datewheel and "snap" over one day. That's a lot of metal and action to not give everything, including a long skinny hand, a bit of a bang.

[StanGMT]

Many thanks, Larry - I will get on to this after New Year.

Stan.

[marshallr47]

I have a circa '67 OP that requires back twisting of the crown to use the hacking feature however on all my modern Rolexes, the second hand stops when I pull the crown all the way to the out position.

I had the OP serviced a little over a year ago and the watchmaker didn't reconnect or adjust the hacking mechanism and it wasn't hacking when I got it back. I brought it back to him and he made an adjustment and now it works.

I would just take it back and have them look at it. Good luck and keep us posted.

[StanGMT]

Thanks, Ron - I will let you know what happens.

Stan.

[SPACE-DWELLER]

About the "hacking": I experienced the same thing on the Zenith SS Daytonas that I have owned. They also did not have the hacking second's function.

[Lol-x]

That's some very interesting information.
I've noticed on one of my watches a while back that the slight reverse pressure on the crown only stopped the second hand in certain positions.
I was not aware and am still not sure whether the second hand should in fact 'hack' so to speak on a vintage watch when the crown is reversed and whether this is an intended design feature of earlier vintage model Rolex prior to the introduction of the pull out crown hack feature. I wish I knew for sure
From what Mireyna says it seems like it is an intended feature for the earlier 'non-hacking' models. It does make sense too, as it allows one to set the second hand to the precise second, otherwise one could not do so, but this is the first time I really gave it more thought.

[abigsecret]

Originally Posted by StanGMT

Mireyna - can you expand on your comment that #2 isn't an issue, please? Are you saying that this 'twitching' of the 24 hour hand when the date clicks over is common? Is it that you would expect the mechanical arrangement of the 1675 movement to produce this effect?

Thanks again,
Stan.

Hi Stan, before I say (type) more, I'm going to do some more research on this particular movement (1575)...

I love this technical stuff, so I'll get back to you!

Have a good night!

Mireyna

[StanGMT]

Thanks Mireyna - I'll be interested to hear what you find out. (By the way - it is the 1675 movement you're going to research, isn't it? I don't know if there is a 1575 movement).

Cheers,
Stan.

[Ironstark]

Hi Stan,
The issue with the 24 hr hand is normal and a characteristic of the watch and it`s design and construction.
The issue with the hand setting is something you may have to have corrected.
On the 1675 GMT`s, the older movements do not have a balance stop lever.
ie; when pulled into handset a lever moves and physically blocks the balance wheel and stops the watch, allowing you to set the time to the second.
On the older movements (like yours by the sounds of it) stopping the seconds hand is achieved by countering the driving force of the mainspring in order to stop the watch. This is done by turning the hands (or to be a little more technical, the cannon pinion which carries the minute hand) backwards. If the friction on the cannon pinion is not sufficently strong enough it will not be able to overcome the mainspring force and you will not be able to stop the centre seconds hand.
To have it corrected it will have to go back to the service centre to have the cannon pinion friction increased.
Hope this helps.

[StanGMT]

Thanks very much, Ironstark.

Actually, I adjusted the watch this morning and the 'hacking' situation seems to be improving - I was able to 'hold' the second hand fairly easily I've only had to adjust the watch three times in the two weeks since I got it back - this morning was the fourth time - and the hacking seems to be getting progressivley better. I have always found that the movement needs about a month of constant use to really settle down after a service, so I'll see how it develops over the next two weeks or so before I decide whether to take it back.

Yours and Mirenya's comments about the 24 hour hand moving in time with the date change are interesting. As I said in my first thread, the movement is so slight it could have been going on a long time - I have only noticed it recently. It would be interesting to know if any other GMT owners have noticed this.

Thanks again,
Stan.

[abigsecret]

The movement number is 1565 GMT or 1575 GMT (1675 is the model number of the watch).
I think all stainless GMT came with 1575, two-tone and all gold came with 1565.
Now if you have a 1565, there is no balance stop lever to stop the second hand when the crown is pulled out. If you have the 1575 movement in yours, there should be a balance stop spring.
It might need to be bent to be effective again.

About the movement of the 24h hand: the date wheel is connected to the 12h wheel (which has the post were the hour hand sits on). The 24h wheel sits over the post of the 12 hour wheel. Because this 24h wheel doesn't connect to a significant power wheel, and moves very freely, the impact of the jumping date wheel can cause this 24h wheel to slightly move.

I hope that makes sense...

Mireyna

[Lol-x]

Thanks very much everyone for all the great technical information, outstanding

[problmchylde]

Originally Posted by Dan Pierce

Sorry Stan, I don't have any answers for ya'. But Mike will be along soon with all the info you'll need.

Questions though, who did the service? Any issues about the age of your GMT?

Thanks,
dP

Agreed.Mike's the man.He loves GMTs......

[East Bay Rider]

Originally Posted by abigsecret

The movement number is 1565 GMT or 1575 GMT (1675 is the model number of the watch).
I think all stainless GMT came with 1575, two-tone and all gold came with 1565.
Now if you have a 1565, there is no balance stop lever to stop the second hand when the crown is pulled out. If you have the 1575 movement in yours, there should be a balance stop spring.
It might need to be bent to be effective again.

About the movement of the 24h hand: the date wheel is connected to the 12h wheel (which has the post were the hour hand sits on). The 24h wheel sits over the post of the 12 hour wheel. Because this 24h wheel doesn't connect to a significant power wheel, and moves very freely, the impact of the jumping date wheel can cause this 24h wheel to slightly move.

I hope that makes sense...

Mireyna

Where were you able to research this information from?

I learn a lot here but must admit that often times I have no idea what you all are talking about.
(yet)

[StanGMT]

Brilliant - thanks Mireyna. And thanks again to you all for enlightening me. As I said yesterday, the 'hacking' problem actually does seem to be sorting itself out and, as the watch was serviced only very recently, I will give it few more weeks to see how it develops before I do anything.

Happy New Year!!!!

[JJ Irani]

Originally Posted by abigsecret

Issue # 2 is not an issue at all....

#1 at the other hand, should be corrected I think. Looks like the balance stop spring is defective.

Good luck!

Hey Mireyna,

Does your beauty and brains go hand in glove?