Ronda Caliber 4120.B

Manufacturer	Ronda
Caliber Number	4120.B
Movement Type	Quartz
Size	12 1/2”’
Diameter Total	28.60mm
Casing Diameter	28mm
Height	4.4mm
Jewels	7 or 3 (see below)
Frequency	32,768 Hz
Battery Cell Number	395
Claimed Battery Life	50 months
Stem	S401-2025
Hand Count	4
Hand Sizes	1.5mm x .90mm x .20mm
Functions	Central hours; central minutes; small seconds at 3:00; big date at 6:00; alarm at 9:00
Hacking Seconds?	Yes
Country	Swiss made or Swiss parts, assembled in unknown
Known Models	Invicta Russian Diver III (Add your watch to the comments below…)

The Ronda caliber 4120.B is a quartz watch movement with a small seconds subdial at 3:00, a double-digit big-date indicator at 6:00 and subdial at 9:00 with an alarm.

Watches with this caliber will have a button on the case around 4:00 for modifying alarm functions.

Swiss Made Vs Swiss Parts:

According to the Ronda website, there are two versions of this caliber 4120.B quartz movement: a Swiss parts version with 3 jewels and nickel plated finish, and a Swiss Made 7 jewel version with gold plated finish (above).

Battery Info:

The 4120.B take a battery cell number 395. The expected battery life for a fresh cell is about 50 months. This will depend on how often you use the alarm.

If you buy a new battery here, your purchase supports the site.

This movement also has a power saving mechanism with pulled out stem (essentially hacking seconds), which lowers the rate of consumption by approximately 70%. In other words, if you are not going to wear your watch for an extended period of time and want to preserve the battery, you can pull the crown out. Just keep two things in mind: make sure your watch is in a safe place with the crown pulled out. You don’t want it to catch on something and break the stem. Also, don’t keep your watch in storage for too long, otherwise you run the risk of the battery leaking acid into the movement.

When changing the battery, be careful when you unscrew the screw… the wishbone style battery strap becomes a cantilever and will fling the screw across the room if you don’t put something over it. One trick is to hold the strap down with your finger (only when wearing gloves or finger cots) or Rodico, then carefully remove the screw with tweezers.

Alarm:

You may notice that there are two springs sticking out of this caliber.

The springs send current to the Piezo buzzer style alarm indicator on the caseback.

What is a Piezo buzzer?

“Piezo buzzers are simple devices that can generate basic beeps and tones. They work by using a piezo crystal, a special material that changes shape when voltage is applied to it. If the crystal pushes against a diaphragm, like a tiny speaker cone, it can generate a pressure wave which the human ear picks up as sound.” –Source

Replacement Prices:

Ronda states that this is a repairable metal watch movement, however, if you need to replace it the prices online range from $48.95 (Swiss parts) to $66.95 (Swiss made) at the time of this post.

Watches with this movement:

The movement featured on this page was found in this Invicta Russian Diver III Alarm watch. If you have a watch with the Ronda 4120.B, please add it in the comments below…

Additional Resources:

• Official tech sheets (pdf)
• More Ronda movements