Seiko Caliber Vs42a

Seiko Caliber VS42A

Seiko Caliber Vs42a

Manufacturer Seiko
Caliber Number VS42A (VS42)
Type Solar Powered (quartz)
Lignes 11.5”’
Casing Diameter
28.6mm
Thickness
3.5mm
Total Height
5.7mm
Jewels
2
Frequency
32,768 Hz
Integrated Circuit
C-MOS-IC
Capacitor Number 302324Y
Stem 351177 (tap 11)
Hacking Seconds?
Yes
Hand Sizes 1.10mm / 0.65mm / 0.20mm
Functions Hours, minutes, central seconds, date at 3:00
Country of Manufacture Japan
Known Models AVI-8 Hawker Hunter Solar AV-4039 (add more in the comments below…)

The Seiko caliber VS42 (actually marked VS42A) is a solar-powered movement with a solar cell underneath the dial which converts light energy into electrical energy that gets stored in a capacitor (secondary battery). The dial of the watch must have at least 30% transparency for the light to reach the solar cell.

We were able to locate technical documents for the VS42A from as far back as April 24, 2015. The most recent tech sheets are from January 11, 2019. There were no noticeable differences other than the layout/design of the documents.

The example movement in this post is signed S. Epson Corp. / 2 / Japan / VS42A / Two Jewels / 712

VS42 VS VS42A:

The movement in your timepiece may actually be signed with the caliber number V157A. As with most (if not all) Seiko movements, the trailing letter indicates the evolution or change-log of the movement, starting with A as the first release. Therefore, V157 is the same as V157A. As of this post, there is not a V157B, V157C, and so on.

Accuracy:

Seiko claims that the caliber VS42A will maintain accuracy of +/- 20 seconds per month at normal operating temperatures of about 5C to 50C (41F – 122F).

Battery Change:

The caliber VS42A is a solar powered watch with a manganese titanium-lithium rechargeable capacitor. It is not a normal battery. The number is MT920, or more specifically: 302324Y (or Seiko part number 4020581). Order one here

Seiko Caliber Vs42a 302324y Capacitor

Charging Times:

The chart below shows how long different lights sources can take to fully charge the cell in the VS42A. This ranges from 47 hours to 5 hours of constant light, depending on the light source type.

Seiko Caliber Vs42 Charging Chart

Power Reserve:

When fully charged, the VS42A has an expected running time of around 6 months. When the power is low, the second hand will skip a second and move in 2 second intervals.

Movement Drawings:

Seiko Caliber Vs42a Drawing

What is 712?

While preparing the macro photos for this post, we noticed a very tiny “712” etched into the movement. It was noticed by the naked eye. It’s still unconfirmed what this 712 represents, so please comment below if you know!

Seiko Caliber Vs42a 712

Replacement Prices:

At the time of this post, replacement prices for the VS42A were found in the range of $24.99 to $39.99 USD.

Additional Resources:

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Colin McPherson
Colin McPherson
3 years ago

Also used in Skagen SKW6278 solar powered watch

SpecOps
SpecOps
2 years ago
Reply to  calibercorner

Sangin Instruments uses this movement in their Dark Merlin model

Jim
Jim
3 years ago

Jack Mason also uses this on it’s Solar watch.

Walter Leonhardt
Walter Leonhardt
2 years ago

The Breil TW1755 is using this mvmnt.

Correctionbot
Correctionbot
9 months ago

Movement.

trackback
In Review: Lum-Tec Vortex D5 | Wrist Watch Review
2 years ago

[…] sort that likes to cycle through different watches, you really don’t have to worry about the VS42A movement running down. Let it sit in the sun for a minute, and it’ll run for a day; give it five […]

trackback
Quartz Movement, Its Advantages and Sophistication – Laikrodis
1 year ago

[…] Seiko caliber VS242A solar quartz movement Image from caliber corner […]

Danny
Danny
1 year ago

Lum-Tec Solar Marine 1 & 2 both use this movement.

Mervyn Hosking
Mervyn Hosking
1 year ago
Reply to  Danny

Are they any good , accuracy? And is the VS42 B the same ?

booker
booker
1 year ago

Sangin Merlin uses this

Mark Fiore
Mark Fiore
11 months ago

Momentum Atlas Eclipse is using this movement now.

CS
CS
6 months ago

Fossil defender FS597X models also have this movement (mine is a blue FS5975, 40mm). It’s annoying that they do not state the model number on the watch web page, only the rechargeable battery reference…

Alessandro
Alessandro
1 month ago

how long does it last its Panasonic MT 920 rechargeable battery before its replacement?

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