Seiko 7A

From Watch Wiki: The Best Watches and Watch Brands
Jump to: navigation, search

The Seiko 7A family was the first analog quartz chronograph movement.

History

Introduced in 1982, this was the first analog chronograph movement with quartz timekeeping and power reserve. It used separate stepper motors for each chronograph function and was decorated and built in accordance with high-end movement standards. The Calibre 7A family was very popular, used in Seiko brand watches as well as many others.

The family was begun with Calibre 7A28, which was the world's first analog quartz chronograph. Calibre 7A38 added a day/date window and is the most common movement in this family, and many know the movement by that name only. There is a great deal of similarity and parts interchange between these movements.

These movements were used in many notable watches. The famous Seiko Giugiaro chronographs features in the movie, Aliens used them, as did the UK Ministry of Defense pilots' chronograph, issued between 1984 and 1990. Cartier produced Ferrari Formula-branded chronographs with the 7A38 and 7A48 as well. Other users of this movement include Yema, Loris, Orient (as calibre J39), Puma (as calibre Y19), Junghans, and Jean Lassale.

All versions of the 7A movement family boasted 10 second per month accuracy except the 7A07, which was only rated to 20 seconds/month.

The 7A movement family was phased out in the 1990's in favor of the less-expensive 7T family. High-end Seiko chronographs now use automatic Seiko 6S and Seiko 8R and Spring Drive Seiko 9R movements.

Variants

  • 7A07 - Quartz stopwatch movement with "bullhead" pushers. The only version with 20 second/month accuracy. Central chronograph seconds, 1/10 second counter at 12:00, 30 minute counter at 6:00. Split pusher at 10:30, 0-reset pusher at 12:00, start/stop pusher at 1:30.
  • 7A28 - Hour, minute, chronograph seconds hands, 1/10 seconds, small seconds, 30 minute counter
  • 7A34 (15 jewels) - 7A38 without the day wheel complication and date at 12:00
  • 7A36 - Hour, minute, chronograph seconds hands, day and date, small seconds, 30 minute counter
  • 7A38 - Hour, minute, chronograph seconds hands, 1/10 seconds with day and date, small seconds, 30 minute counters
  • 7A48 - Hour, minute, chronograph seconds hands, 1/10 seconds, small seconds, 30 minute counter, date and moon phase subdial
  • 7A54 - Lassale pocket watch movement, identical to the 7A48 but with a gold-anodized backplate
  • 7A74 - Lassale movement, based on the 7A34 with the date wheel from the 7A38 showing at 4:30 and gold-anodized backplate

External Links

See Also