Seiko 3820A

	Brand:	Seiko, Suwa Seikosha
	Family:	Suwa Seikosha 38 Quartz Stream
	Height:	5.30 mm
	Jewels:	7
	Reserve:	hours
	Frequency:	16,384 Hz, 32,768 Hz
	Winding:	Battery
	Diameter:	25.60 mm (11.5 ligne)
	Complications:	Hacking Seconds
	Hands:	Central Hour Hand, Central Minute Hand, Central Seconds Hand

Cal. 3820A was an early high-end quartz movement. It was produced by Suwa Seikosha from 1972 through the 1970s and was used in high-end Seiko models with the name 38SQ. A similar movement with a calendar complication was Cal. 3823A (38SQW). It was preceded by Cal. 35A, Seiko’s first-ever quartz movement, in 1969 and replaced by the “Grand Quartz” Cal. 4840A in 1974.

This movement was differentiated in the Cal. 38 line by its use of thermocompensation and a fine adjustment mechanism. Unlike the lower-end models, Cal. 3820A included 9 condensers of different capacities attached to the electronics module. This allowed fine adjustment of the movement through the replacement of tiny contact spring pins. Later versions of the module included a conventional screw-type variable condenser, and many examples include this instead.

It was fitted with 7 jewels, a large number for the time and more than most later quartz movements. Early examples used a 16 KHz crystal, but this was upgraded to 32 KHz later in the production run and many examples were retrofitted with this component.

Cal. 3820A was accurate to 5 seconds per month when new, and most watches using it were labeled “V.F.A.” (“Very Fine Adjustment”), Seiko’s second-to-top accuracy rating at the time. It was replaced by the “Grand Quartz” Cal. 48 and can be seen as a predecessor for today’s high-end Grand Seiko Quartz movements.

Cal. 3820A Applications

Cal. 3820A was used in a variety of watches throughout the 1970s. It began in expensive steel-cased models simply labeled “Seiko Quartz” and using the “38SQ” name in catalogs. It was positioned above the rectangular Cal. 39 watches produced by sister company, Daini Seikosha.

By 1975, it was offered in many upscale quartz watches in the “HMC” line, most with the “V.F.A.” label (for “Very Fine Adjustment”) and some with gold cases and bracelets. Here, it fell just below Cal. 3883A and the “Superior” line.

Suwa Seikosha 38 Stream Overview

Seiko’s Cal. 38 series was the first volume-production quartz movement family from Seiko. The architecture and design set the template for all future quartz movements, and it was the premier product that pushed Seiko to the top of the watch industry in the 1970s. Cal. 38 movements were positioned in the mid-range to superior market segments, including the “QT”, “QR”, “SQ VFA”, and “GFA Superior” lines.

Seiko was quietly racing to develop a quartz watch movement in the 1960s, and delivered their first Cal. 35 movement to the Neuchatel Observatory in late 1967, just a few months after the CEH delivered their “Beta” quartz movement prototypes. A product of Suwa Seikosha, Cal. 35A used a 8,192 Hz of 16,384 Hz quartz crystal and an integrated circuit from Intersil in the USA. Seiko offered Cal. 35 SQ for sale in the Seiko Astron watch on Christmas Day, 1969, with 100 examples sold in the first month. Suwa rival Daini Seikosha developed their own movement, Cal. 36, and launched it in 1970, but neither movement was truly produced in volume.

Cal. 380x were the lower-end movements but were still accurate to 2 minutes per year. However these movements lacked any adjustment beyond replacement of the condenser block. Cal. 382x included a thermocompensation circuit and was accurate to 1 minute per year. It could be regulated using a step variable condenser. All basic movements used 7 jewels: Two each on the third wheel, sweep second wheel, and step rotor, and another used on the seconds hand finger.

Suwa Seikosha 38 Stream Technology

Suwa Seikosha developed Cal. 38 as a full-production midrange to high-end quartz movement, and it incorporates many features that now seem commonplace but were groundbreaking at the time. The quartz crystal oscillated at 16,384 Hz and it used a CMOS integrated circuit to reduce battery consumption, though later examples used a 32 KHz crystal. The hands were operated by a stepper motor and a jeweled backlash pin ensured a smooth dead beat seconds hand. The earliest examples were sold as “VFA” (“Very Fine Adjustment”) and were adjusted for temperature and in 6 positions.

Early examples of Cal. 3823 use a large 16 KHz quartz tube and unusual “step variable condenser” regulation system using multiple contacts for variable resistance. The design was evolved over time to use a more integrated quartz module and smaller ICs as technology advanced. The final Cal. 3823A had a small 32 KHz quartz tube and modern screw-type trimmer condenser for adjustment. The circuit block and crystal oscillator were also combined in later examples. These components could be retrofitted to earlier movements, and many were during service. 16 KHz examples are rare today.

These movements were produced in larger volume but were still quite high-end compared to mass-market quartz watches later in the 1970s.

Suwa Seikosha 38 Stream Family

All 38×3 movements were branded “38SQW” or “38QTW” and included day and date. Cal. 38×2 is branded “38QTC” and is date-only. Cal. 38×0 was branded “38SQ” and lacks the calendar function.

One unusual (and rare) version is Cal. 3819A, used in “38DQC” models called Dual-Zone Timer. This was Seiko’s first GMT quartz watch. Even rare is Cal. 3870A, a time-only version used as “38RW” in Seiko’s first quartz railway watch, model QYE010 (3870-0010).

The 38SQ “VFA” line was replaced by the 48GQ “Grand Quartz” and 48SQ “Superior” line. The 38QT “QT” line was replaced by the 08KQ “King Quartz”, 38QR “Lord Quartz”, and 08QT line. The QR line of watches were replaced by the cheaper “Type II” models.