MINUS4PLUS6

ETA 7750 Watch Assembly

 

I have always been curious to owning a chronograph. Although my daily wearers are Rolex GMT's, I wanted to experience a chronograph, so I decided to build one.

This particular watch was sourced from vendors in Cairo and Germany. Using eBay, the case, face, and hands were ordered as a set from Germany, and the movement, date and Italian day wheel came from Egypt. The two-piece Martac band was sourced from Westcoastime.

After purchasing the parts, I had the watch cased and pretty well regulated, but when I went to fit the winding crown, I made the mistake of removing the stem while the watch was in the hand-setting position, rather than in the winding position. Subsequently, the stem would not fit back into the keyless works. The only way to fix the stem, was to remove the face, hands, and take the watch down to the base plate on the dial-side. With some encouraging words from AWCI member Haris Durakovic at USA Watch Service, I tackeled my first 7750 partial disassembly.

7750 Complete

Click on the photos for a larger images.

An early morning picture of my workspace. I was up early to tackle this job. Being caffiene-free helps.

The parts tray has all the removed pieces. I decided to snap this image only after I disassembled the watch.

bench
This is the parts tray showing the removed rotor, hands, and Italian day wheel. hands-day
Here is the movement in the movement holder with the face, hands, and day wheel removed. date

Using Macromedia clips from ETA showing how to disassemble a 7750 movement (also purchased from eBay), I was able to remove the day-date plate and take the movement down to the base plate. The online version of this CD is posted here.

This view shows some of the plastic parts used in 7750.

Alliance Horlogere has a great video on assembling a 7750 (downloadable), and TimeZone also has a good review. (.pdf here).

baseplate exposed
This is a top view looking down at the keyless works. The lighted area highlights the keyless works portion of the movement. I had to loosen one screw to allow the stem to seat back into the keyless works. Once the stem was seated, I could hear the escapement moving again; it was like I brought the patient back to life hearing the ticking of the escapement. With the balance ticking, I know that I had the stem in the proper position. keyless works

The next challenge is reassembling the movement without having screws or springs fly out of tweezers.

Fortunately, everything went back in place just fine.

date installed
face hands No second hand
The next challenge was reinstalling the hands. Chrono hands are hard to install because they are smaller, and the 30 minute totalizer and the large second hand are on loosely spinning cams. Essentially, the hands had to be placed perfectly prior to pressing down onto the pin. The other hands can be installed and then slightly corrected with peg wood as the pins are tied driectly to geared wheels whereas the 30 minute totalizer and large second hand would just spin in their cams when being adjusted with pegwood.
With the hands and face installed, the movement is installed back into the case. The winding rotor was removed earlier in order for the movement to fit into the movement holder. Open caseback
With the movement seated, and the rotor installed, the caseback is screwed down. caseback
Here is the 7750, along with a 2824 watch I made for my son's 12th birthday. My son's watch case, face, hands is sourced from Otto Frei and the ETA 2824 movement from TimeZone's SalesCorner. 7750 and 2824
This is a view of the casebacks. Look closely and you will see my son's name engraved on the winding rotor. casebacks
This is a better view of the 7750 balance and rotor. This is a 25 jewel movement. You can see the jewel holding the 30 minute totalizer. Older 17 jewel movements do not have as many jewels on high-torque pivots and have more plastic pieces. 7750 Balance

The watch complete. So far, this has been a great watch. It runs a little fast, but slows down when the chrono is running. It is 40mm face and 15mm tall which makes it a little taller than a Submariner. The weight is comparable to wearing a GMT-C. A great project.

My next challenge is refitting the 30 minute totalizing and center second hands, but only after when I have some spare hands ordered.

7750 Complete