Early Eta GMT/EXII 24 Hour Hand Modification

[automatico]

I recently had the 'pleasure' of working on a "1655" that I bought new 4 or 5 years ago because I finally decided to repair it...the date had been hanging up half way in the window since new.

This Asian (not Eta factory) 24 hour modification was used on earlier models that have the 24 hour hand geared directly to the 12 hour time and the 24 hour hand is not adjustable at all other than removing the hands and remounting them.

Hand stack from dial up:

24 hour hand

12 hour hand

minute hand

second hand

The new gearset drives the date jumper as usual with a gear added on top to drive the 24 hour wheel. It sounds simple and it is.

They usually do not give any trouble at all...as long as everything is correct to start with. Mine was not.

The usual problem with this modification is hands rubbing or hanging up because they are just too close together. They stuffed 4 hands in a 3 hand space.

The first thing I did was cement the rolexfont datewheel back on the Eta datewheel because it was loose (not uncommon). I stuck it on with two part slow set epoxy being careful to line the date up inside the date window and making sure the datewheel was not mounted off center. This part was easy.

Next, I swapped the entire (genuine) Eta 2824 (28800 bph) that came in the watch for a slower beat genuine Eta 2846 (21600 bph) to mimic the rolex (19800 bph).

First off, the datewheel was rubbing the dial a tiny bit and the date did not flip! quickly so I put some dial dot strips between the calendar spacer and dial to give a little extra clearance. Nothing to it but after putting it all back together, I still had the trouble with the date flipping half way in the window or not at all. I was not surprised.

I have had to space the dial away from the calendar spacer ring a few times in the past so it was not out of the ordinary. This did not fix any problem other than the datewheel lightly rubbing the dial.

The date was still hanging up half way in the window.

Here is where the trouble was:

When they add a extra gear to drive the 24 hour wheel to the movement, the new gear sometimes rubs the plate that screws down over the date wheel jumper spring. Let's call the plate that goes over the date jumper spring the 'date jumper spring guard'. You can not usually tell the wheel is dragging on the date jumper spring guard until the 12 and 24 hour hands start getting out of correspondence over and over for no apparent reason. Take the movement out, mount the hands in correspondence and blooey!, they are out of whack in a few hours because the double gearset slips where it is pressed together when it drags on the date jumper guard...while the watch still runs and keeps 12 hour time as usual (depending on how tight the double gear is pressed together).

I said WTF! over and over because I never suspected the double gear was slipping where it is pressed together...I had it apart a half dozen times.

What was happening was the date jumper spring guard was rubbing on the lower of the two gears on the modified type gearset and did not show an indication of rubbing until later after everything was back together.

The fix:

Remove the date jumper spring guard and file the contour a little deeper where the plate is cut out to clear the original idler gear. There is never a problem with the guard rubbing the original idler gear, it only rubs when the 24 hour gear is added.

Note:

Be careful not to remove too much material because there is a ledge made on the guard to hold the gear down.

Next...be super careful mounting the date jumper spring and jumper spring guard under the glued on (bigger ID) rolexfont datewheel. Make sure the datewheel is level all around the movement plate because you can no longer see (under the rolexfont datewheel) where the date jumper spring and date jumper guard are seated because the glued on datewheel obstructs the view.

One sure hint of trouble to come is when the screw that holds the date jumper spring guard on top of the date jumper spring does not bottom out solidly when screwed down. If the screw feels like it is not seating...you will have trouble.

After the date works are assembled and before all 4 of the hands are installed, it is a good idea to mount the dial and let the movement run at least 24 hours with only the 24 hour and 12 hour hands mounted.

Why?

1...to make sure the date still flips with both hands pointing to 12 midnight

2...to make sure the 24 hour and 12 hour hands stay in correspondence

3...to make sure the date flips! crisply and does not fail to flip or flip half way because it is dragging on the date jumper spring or guard

4...it is easier to r/r two hands than four

If you are in a hurry...you can cheat by running the hands ahead about 23 1/2 hours and wait only 30 minutes until it flips. The watch needs about a half hour to get all the slack out of the 24 hour hand gears etc so the 24 and 12 hour hand position can be checked at 12 midnight.

Tips:

With the dial mounted and the time somewhere between 6am and 6pm (just to be safe), flip the datewheel around a least 31 days by the quick set to be sure that:

1...all the teeth on the datewheel are Ok and it does not miss a day

2...the datewheel does not drag the dial or movement plate

If when quick setting the date, the date setting feels 'crunchy':

1...the date is trying to change or has just changed (no harm is done because the date jumper is designed for this)

2...the datewheel is dragging the:

a...movement plate

b...date jumper spring (not installed correctly)

c...date jumper spring guard (not installed correctly)

d...screw that holds the shiny plate on the 3 o'clock side of the movement (this plate holds the datewheel in place on the 3 o'clock side and covers the setting parts etc...the screw has a large flanged head and can rub the under side of glued on rolexfont datewheels)

This modified GMT/EXII with glued on rolexfont datewheels and non adjustable 24 hour hand can sometimes have a problem but it's still not anywhere near as bad as the modified Eta GMT/EXII with adjustable 24 hour hand.

Here are some good 2824 pictures and you can see the date parts in the 5th picture from the top:

http://www.chronometrie.com/eta2824/eta2824.html

Looking at the picture, all the trouble is on the left side and you can see the standard idler gear between the cp and date jumper. The GMT/EXII modification has another gear installed on top of the idler gear between the c/p and date jumper and this is where all the trouble starts...and the oversized glued on datewheel just makes matters worse when you have to r/r all this stuff.

The 'big head' screw that might rub add on rolexfont datewheels is to the right of center, holding the shiny plate down. Most of the time it is Ok.

Update 5-20-09:

The watch went back to its old tricks...the 24 hour hand started getting out of whack after repairing the initial problem posted above. What happened this time around was the little tiny gear on the Asian made date jumper idler gearset that drives the 24 hour wheel was slipping on the internal tube it is pressed on. It was just too loose on the internal drive tube because of all the slipping it had endured (during setting etc) when it was rubbing the idler gearset. It did not seem to slip at first but started a few hours later after 'final assembly', probably because of setting the time over and over.

I doubt there is any such thing as 'final assembly' with these things.

The fix was to remove the hands, dial, datewheel etc (for about the 13th time!), remove the idler gearset, and stake the tube that the 24 hour gear is mounted on.

Just set the gearset on a staking tool table and lightly stake the tube using a three point punch.

Note:

The idler gear that drives the 24 hour wheel is pressed on a tiny tube that comes up even with the gear at the top so the tube can be staked to make it tighter inside the gear. Since this part of the tube is above the post it runs on, staking the tube does not matter as far as increased friction etc is concerned.

Staking the tube with a three point punch expands the tube slightly to increase its grip on the 24 hour drive gear. This Asian made idler gear is just hit or miss as far as being tight enough not to slip when new. Most are Ok as long as they do not drag on the date jumper spring guard.

All this taking apart and putting together did not do much visible damage but sometime during one of the take apart sessons, I knocked the hand setting tool over on top of the dial and put a tiny mark on the edge of the dial. Fortunately, the mark is under the case where the dial mounts and does not show. The only other wear and tear that shows is where some of the black paint on the hubs of the hands flaked off. This happened on the first or second take apart and could not be avioded.

Since I had to run the hands around a few dozen times, I oiled the canon pinion at first and it still seems to be Ok. The 2824/36 etc has a fairly rugged c/p setup.

All this bla, bla, bla makes the fix sounds lot harder than it is. Once you get tha parts out and look them over, the fix is fairly easy.

I tried to post this in the technical section but could not. Anyone wants to move it...fine with me.

[freddy333]

Great post, Auto. Hopefully, it will get copied to the appropriate place.

[stilty]

nice post. i have yet to encounter one of these beasts, but if I ever do, I know who to turn to for some advise!

[willieboy123]

Great Post thanks for taking the time!