Quartz Ronda 751: Direct Handwinding Mechanical Movement Replacement?

[RJC87]

Hi guys! I have a watch that uses a Ronda 751 quartz movement (see pic). For those unfamiliar, it’s a small tonneau shaped movement - usually a woman’s size (5½ x 6¾ linge and 2.5mm thick) with the following specs:

Linge Size: 5½ x 6¾, 2.50mm thick

Hand Size: 120/70

Stem: 401-1237

Cell/Battery/Power Source: 379

Tap Size: 10

 

I’d like to replace it with a mechanical movement: I started off looking for a direct drop in replacement but it’s proved very difficult. I haven’t found any modern movements with the same dimensions (although to be fair I haven’t had much luck finding a comprehensive listing of modern movements available). As far as the vintage movements go, (from here: http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk) the ETA 2480 (http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&ETA_2482) is a good example of the vast majority of what’s available— the right dimensions but 1mm too thick. And for a 2.5mm movement, 1mm is a ton. 

 

The Tissot 530 (http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Tissot_530), and Enicar 672/678 (http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Enicar_672) are the 2 that seem closest but they are still a half mil too thick. And worse, even if it fits, where would I even begin looking for one?

 

Does anyone one have any knowledge of a movement that would work or one I could modify a bit to fit? Or any idea the best place to look??

 

Thanks in advance for the help and I love the forum!!

[rodabod]

Pay attention to the “T” value which is stem height as that is critical that it’s close in value. 

[StuartBaker104]

I would say that this is a problem you are unlikely to solve.

2.5mm mechanical movements do exist, but movements that thin are few and far between. You can check out a few of the manufacturers sites... ETA, Miyota, Ronda, etc and Cousins has brochures of Chinese movements. The only modern movement I saw that thin is the ETA7001, which is round and way too large.

Vintage movements were rarely that thin as you will have found from Ranfft.