Why the CHS GMT movements are failing

[2fake4u]

I have a 2893, sitting in my toolbox. I had two watchmakers give up on making it work in my bp 116713. do you know how to install it without getting new hands? also, my guy couldn't source a green gmt hand, it was red.

if you get the ICHS model, you can use those hands. otherwise, you will have to buy new hands. ebay has everything youll need.

 

[2fake4u]

do these issues apply to all REP GMT, or just the Rolex Master II? I just ordered a Breitling Navitimer World and am curious if I may encounter the same problems.

if it has hour, 24hr, minute, second hand stack, it will have these issues.

if it has 24hr, hour, minute, second hand stack, it will still have issues, but they arent as common as this one.

There are only so many GMT movements out there

 

[2470f2.8ii]

if you get the ICHS model, you can use those hands. otherwise, you will have to buy new hands. ebay has everything youll need.

I wish man but my guy said they wouldn't fit...?

we ended up just keeping the 2836 ichs.

I have a wyler 2893-2 gmt

do you think you can install it?

 

[d4m.test]

if it has hour, 24hr, minute, second hand stack, it will have these issues.

if it has 24hr, hour, minute, second hand stack, it will still have issues, but they arent as common as this one.

There are only so many GMT movements out there

Looking at the pics, it's the later., so I guess that's good.

 

[ffuhcu]

Looking at the pics, it's the later., so I guess that's good.

The Navitimer World is an A7750 (A7754?) so a different movement to those used in the Rolex GMT reps. I don't remember reading GMT-specific issues with that movement, although general A7750 guidance would apply.

 

[JackJ1980]

Thanks Craig !

 

[d4m.test]

The Navitimer World is an A7750 (A7754?) so a different movement to those used in the Rolex GMT reps. I don't remember reading GMT-specific issues with that movement, although general A7750 guidance would apply.

The TD has the movement listed as: Asia 7750 Valjoux Working Chronograph Movement + GMT Movement, 28800bph, Insignia Rotor

when you mention "general A7750 guidance would apply" I assume you're referring to the finicky chronograph??
Thanks for the info!

 

[Eagl3]

The TD has the movement listed as: Asia 7750 Valjoux Working Chronograph Movement + GMT Movement, 28800bph, Insignia Rotor

when you mention "general A7750 guidance would apply" I assume you're referring to the finicky chronograph??
Thanks for the info!

The 7750 natively supports the GMT module. You won't have issues with it.

And the general guidelines for the 7750 are:
1. Wind very carefully. The gearing is quite high and you can strip it if you wind too fast.
2. Don't change the date between 10pm-2am
3. Don't reset the Chrono when the seconds hand ISN'T between 10 and 2 on the dial (heart cams will slam and these aren't as strong as the swiss ones)
4. Don't reset the Chrono while it's running. Stop it first (there's a cam to stop this, but it's made of chinesium)
5. Don't set the time backwards (rule of thumb for most watches).

 

[d4m.test]

The 7750 natively supports the GMT module. You won't have issues with it.

And the general guidelines for the 7750 are:
1. Wind very carefully. The gearing is quite high and you can strip it if you wind too fast.
2. Don't change the date between 10pm-2am
3. Don't reset the Chrono when the seconds hand ISN'T between 10 and 2 on the dial (heart cams will slam and these aren't as strong as the swiss ones)
4. Don't reset the Chrono while it's running. Stop it first (there's a cam to stop this, but it's made of chinesium)
5. Don't set the time backwards (rule of thumb for most watches).

awesome information - thanks!

 

[Nur-Uhr]

Very informative thread about the A3186 movement of the GMT.
The Yuki transformed version sounds good but also expensive.
Would a GEN 3186 movement fit in the Noob case?

Best solution is actually to avoid the 2nd position of the crown and not to set the date with jumping hour.
Ok something what is possible but not so comfortable at all.

Very good summary of the A3186 fault.

 

[Youdno]

Thanks for the insight!

 

[knol]

seems a lot of the newer 3187 movements arent having issues. ive yet to tear one down to see if they beefed up the spring or what they did, but so far, ive had a half dozen come through that didnt have issues, and they were all purchased in the last couple months.

did you find our if they made and modifications to the movement to make it more reliable ?

 

[Dr Fun Socks]

Hey gang. I finally had a chance to dig into a CHS GMT Master II with a "broken" jumping hour hand. Thought I'd share what I found since I've hand several members reach out with issues.

So props to the rep factories for trying to engineer a solution to get the hand stack correct. Unfortunately, it fails in execution. In short, the parts are so thin and frail that I imagine this will continue happening until it's fixed.

The Jumping Hour is made up of 2 gears which sandwich a spring. Here is a gen 3185/86 version from my watch:

A strong, thick spring holds those massive fingers against the grooves. Now compared to the Asian solution:

And with the top on:

The spring has to be strong enough to move the top and bottom gears together when the watch is running but have enough give to let them jump independently when adjusting the hour hand. Unfortunately that spring is not up to the task.

As these are custom pieces there are no replacement parts. The only things that can be done are to A.) just live with whatever state the watch is in when broken or B.) glue the top and bottom gears together and reset the hands. This will insure that they don't become out of sync but you will not be able to adjust the hour/GMT hand independently.

Sorry for the bad news guys. Maybe the factory will engineer a better solution but I'd either never adjust the jumping hours or steer clear!

-TickleShoes

So im a bit late to the party here but ive just opened up a chs movement i just received, and using a 25x loop im guessing the spring is snapped as in your post Tickleshoes it is meant to be a solid wavey loop spring and not have the break in it? Im going to try gluing the wheels together and sacking off the independent gmt hour function, using epoxy. Ill write back if it works but im guessing by this point people have kind of given up on chs movements! Honeslty if the bloody wheels didnt slip and i could change the date whilst winding i wouldnt of even bothered opening it up but man this thing is a paint in the ass!

 

[Dr Fun Socks]

Broken at almost the exact same spot!

 

[Dr Fun Socks]

Small update, the epoxy worked well! Let it cure for 24 hours and stuck it in this afternoon. Date now changes great, wound it through 20 date flips (who ever invented the quick date change, i owe a pint to because winding is long!). Seems to be holding up well, again ill report back if it breaks. I know tickleshoes one didnt last long and hes an actual watch maker not a goon with some tools so we’ll see how it goes!

 

[RollieFingerz]

So glad I found this thread! thank you guys! super informative..and I will purchase the ICHS models which does not seem like a big difference to me as long as I can adjust the GMT hand.

 

[KJ2020]

Small update, the epoxy worked well! Let it cure for 24 hours and stuck it in this afternoon. Date now changes great, wound it through 20 date flips (who ever invented the quick date change, i owe a pint to because winding is long!). Seems to be holding up well, again ill report back if it breaks. I know tickleshoes one didnt last long and hes an actual watch maker not a goon with some tools so we’ll see how it goes!

Did you reset all the hands? I think the issue he mentioned was the hands wouldn't stay aligned. And I guess we could set the GMT hand to GMT time and salvage some functionality. Or match it to local and effectively have a 4 digit or GMT Master I movement.

 

[Dr Fun Socks]

Did you reset all the hands? I think the issue he mentioned was the hands wouldn't stay aligned. And I guess we could set the GMT hand to GMT time and salvage some functionality. Or match it to local and effectively have a 4 digit or GMT Master I movement.

Well i live in england so set gmt to normal time! Reset all the hands though. Something strange happened over night, the gmt hand stayed at the right time but i lost about 3 hours on the hour hand... all still winds well though which was the problem before, the gmt spring slipped near date change hence the glue. I kept it on a winder so shouldn’t be a power issue. Strange, ill keep monitoring it! Also yes the gear train is looser than a wizards sleeve so the alignment is ok at best...

 

[Dr Fun Socks]

Ok so it seems the hour wheel must have an issue. I havent taken it apart yet, im off on holiday for a couple of weeks so it will have to wait, but the time setting function is fine, but when running only the hour hand stops. I find this very weird because im pretty sure the gmt hand runs from the hour hand (at least in the setting mode it does) so no idea whats happening! The guy I bought the watch from tried to glue the stem back in because of the keyless issue.... probably related!

 

[Duckguy]

Another one bites the dust. Really not sure what I'm going to do to try and fix this, but what a pain. I'm half considering fabricating a new spring from higher quality metal. Should be interesting and blinding to try.