Ronda Caliber 3520.D

Brand	Ronda
Caliber Number	Ronda 3520.D
Type	Quartz
Size	10 1/2”’ x 11 1/2”’
Diameter	26.2mm
Thickness	4.9mm
Battery Cell Number	384 (1.5 V)
Claimed Battery Life	54 months
Jewels	4
Hacking	Yes
Hands	1.50mm/0.90mm/0.25mm
Functions	Hours, minutes, central chronograph seconds, 30 minute counter, 12 hour counter, small seconds, date
Country	Switzerland (Swiss parts version also available)
Known Models	Chronologia Aviator Chronograph, CT Scuderia Coda Corta (add yours in the comments)

The Ronda caliber 3520.D is a quartz chronograph from Ronda’s Startech line of watch movements. Official Ronda documentation states that this caliber can have subdials at 6:00, 9:00 and 12:00, but we have only seen it with subdials at 6:00 and 12:00. If you know of a 3520.D powered watch with 3 subdials, please comment below.

Swiss Made VS Swiss Parts:

According to the Ronda website, there are two versions of this movement: a gold plated Swiss Made version and nickel plated Swiss parts version. They both have 4 jewels. Ronda also considers this movement to be repairable.

Power Saving Feature

The battery is claimed to last about 54 months in normal conditions, but if you are not going to wear your watch for a while, the 3520.D has a power saving mechanism when the stem is pulled out stem (aka hacking function). Reduction of battery consumption approximately 70%. It is not advisable to leave the chronograph second hand running because it will drain the battery faster and put more wear and tear on the gears.

Accuracy:

According to Ronda, the caliber 3520.D should keep time within -10/+20 seconds per month with an operating temperature of 0 to 50 degrees Celsius.

How to change the battery:

There are two screws holding the battery cover down. Carefully remove the two screws (don’t lose them!) and lift the battery cover off. Replace the battery with a 384 cell. Put the battery cover back on, do not fully tighten the first screw until the second screw is in. Make sure the orange insulator is in place.

Resetting the Chronograph to Zero:

After changing the battery, your chronograph seconds hand or subdial totalizers may not be not lined up to zero. You can use the following sequence to get everything lined up:

1. Pull the crown out two clicks to time setting position (position III).
2. Press button A (top chrono button) and B (bottom chrono button) together for at least 2 seconds.
3. The chronograph seconds hand will spin around one full turn, this is how to know you’re in correction mode.
4. Press button A to advance the main chrono hand forward until it gets lined up. Long press to make it advance faster, short press for one second intervals.
5. Press button B to go to the next hand.
6. Press button A until the hand is lined up.
7. Press button B to advance to the next hand.
8. Press button A until the hand is lined up.
9. Press the crown back in to position I.

Note: In the unlikely situation that the hands still won’t line up, or if they are moving around, there is a chance the hands are loose and need pressed back on.

Stem Removal

To remove the crown/stem, find the hole with the arrow. While the crown is in position 0, pressing this with your tweezers or other tool will allow the stem be unlocked so you can pull it out. Do not press too hard.

Replacement Price:

At the time of this post, replacement prices were found online for $49.95.

Watches With This Caliber:

The caliber 3520.D below was found in a CT Scuderia Coda Corta Chronograph watch here.

Video:

Additional Resources:

• Official 3520.D datasheet
• Official 3520.D tech sheets