Seiko 4R37A Quick start guide

PARTS LIST /TECHNICAL GUIDE
Movement size
 • Diameter 
Outside: Ø 27.4 mm
   Casing: Ø27.0mm
 • Height:   5.32mm
Automatic Cal. 4R37A
[SPECIFICATIONS]
Item Cal. No.
Loss/Gain
Dailyratewornon
thewristat
temperature range
between5°Cand
35°C)
Between+45and-35seconds
Standardratefor
measurement
Mainspringwind
upstatus Fullywindup After24hours fromfullywindup
Testingpositions Dialupward:
T0(CH) 6o’clockatthetop 9o’clockatthetop Dualupward: T24(CH)
Measurement
(dailyratein
seconds:s/d)
±20s/d ±30s/d ±30s/d
(Isochronism
fault:T24-T0)
±30s/d
Regulation system ETACHRONSystem
Lift angle of the escapement 53°
Power reserve Fromfullywoundtostoppage:Approximately40hours
Number of jewels 24jewels
4R37A
Movement size
Outsidediameter Ø 27.4 mm
Casingdiameter Ø27.0mm
Height 5.32mm
Driving system Automaticwindingwithmanualwindingmechanism
Time indication
• 3hands
(Hour,Minute,andSmallsecondhands)
• Dateindication
•24-hourindicator
Additional function •Datecorrectionfunction
•Secondhandstopfunction
Crown
operation
Normalposition Manualwinding(clockwiseonly)
1stclickposition Datesetting(counterclockwise)
2ndclickposition Timesetting(Hourandminute),Secondhandstop
Vibration per hour 21,600(5beatspersecond)
 • 3hands
  (hour,minuteandsecondhands)
 • Dateindication
 • 24-hourindicator

Cal. 4R37A
PARTS LIST
2/21
SEIKO Automatic Mechanical Cal. 4R37A is based on Cal. 4R35B.
This watch has a small 24-hour clock in the 10 o’clock direction.
FEATURES
CHARACTERISTICS OF A MECHANICAL WATCH
1. This mechanical watch operates using power obtained from a mainspring.
2. While loss/gain of a quartz watch is indicated by a monthly or annual rate, accuracy of a
mechanical watch is normally indicated by a daily rate (loss/gain per day).
3. Normal usage accuracy of a mechanical watch varies according to conditions of use (time
period that the watch is worn on the wrist, temperature environment, hand movement, and
winding state of the mainspring).
4. When the watch is affected by strong magnetism, it temporarily gains or loses time. If the
watch encounters a strong magnetic field, the parts of the watch may be magnetized. In this
case, repairs such as removal of magnetism are required.

Cal. 4R37A
PARTS LIST
3/21
→Please refer to the following pages.

Lubricating: Types of oil Oil quantity
AO-3 (Moebius A) Liberal quantity
SEIKO Watch Oil S-6 Normal quantity
SEIKO Watch Oil S-4
Disassembling procedures Figs. : 153
Reassembling procedures Figs. : 53
1
[CALENDAR MECHANISM 1]
DATE DISK GUARD SCREW
0012 354
DATE DISK GUARD
0808 183
DATE DIAL
DATE JUMPER
0810 183
❷
③
❹
⑤

Cal. 4R37A
PARTS LIST
4/21
→Please refer to the following pages.

Lubricating: Types of oil
AO-3 (Moebius A)
SEIKO Watch Oil S-6
SEIKO Watch Oil S-4
[CALENDAR MECHANISM 2]
INTERMEDIATE WHEEL
FOR DATE SETTING E
0962 025
GUARD FOR DATE
CORRECTOR SETTING
TRANSMISSSION WHEEL
SCREW
0012 485
GUARD FOR DATE
CORRECTOR SETTING
TRANSMISSION WHEEL
0836 183
INTERMEDIATE WHEEL FOR
DATE SETTING C
0962 185
INTERMEDIATE WHEEL FOR
DATE SETTING B
0962 023
DATE SETTING WHEEL
0737 183
DIAL HOLDING SPACER
4408 ***
MINUTE WHEEL AND PINION
0261 183
INTERMEDIATE DATE
DRIVING WHEEL AND PINION
0817 300
24-HOUR WHEEL
0157 182
CANNON PINION
0225 417
⑮
HOUR WHEEL
0273 184
LOWER
SHOCK
ABSORBING
SPRING
LOWER SHOCK
ABSORBING CAP
JEWEL
LOWER HOLE JEWEL FRAME
FOR SHOCK-ABSORBER
⑩
⑫
⑨
⑭
⑯
⑰
24-1
0014 577
0011 220
0014 295
⑬
⑪
24-1
24-1
*1
*1
*2
*2
*3
*3
⑥
❼
⑧

Cal. 4R37A
PARTS LIST
5/21
→Please refer to the following pages.

Lubricating: Types of oil
AO-3 (Moebius A)
SEIKO Watch Oil S-6
SEIKO Watch Oil S-4
[BALANCE AND ESCAPEMENT]
OSCILLATING WEIGHT WITH BALL BEARING
Refer to SEIKO Web Parts Catalogue.
0509 ***
BALANCE BRIDGE SCREW
0012 420
BALANCE COCK
0171 353
BALANCE
COMPLETE WITH
STUD
0310 197
UPPER SHOCK
ABSORBING
SPRING
0014 577
UPPER HOLE JEWEL
FRAME FOR SHOCK-
ABSORBER 0014 295
UPPER SHOCK
ABSORBING CAP
JEWEL
0011 220
AUTOMATIC TRAIN BRIDGE
0191 183
SECOND REDUCTION WHEEL AND
PINION
0514 183
RATCHET WHEEL SCREW
0012 919
RATCHET WEEL
0285 051
PALLET BRIDGE SCREW
0012 354
PALLET BRIDGE
0161 300
PALLET FORK
0301 009
AUTOMATIC TRAIN BRIDGE SCREW
0012 354
󱢾
㉒
❶
㉖
㉕
󱣀
󱣂
㉗
24-2
24-3
24-4
24-1
⑳
⓲
⑲
󱣁
*1
*1
*2
*2
*3
*3

Cal. 4R37A
PARTS LIST
6/21
→Please refer to the following pages.

Lubricating: Types of oil
AO-3 (Moebius A)
SEIKO Watch Oil S-6
SEIKO Watch Oil S-4
[WINDING MECHANISM]
󱣅BARREL AND TRAIN WHEEL
BRIDGE SCREW
0012 420
CAP JEWELLED SPRING
0015 703
CAP JEWEL
0011 221
SLIDING CROWN
WHEEL SPRING
0363 184
BARREL AND TRAIN WHEEL
BRIDGE WITH HOLE JEWEL
FRAME
0114 183
LOWER PLATE FOR BARREL
AND TRAIN WHEEL BRIGDE
0436 164
THIRD WHEEL AND PINION
0231 070
LOWER PLATE FOR BARREL AND
TRAIN WHEEL BRIGDE SCREW
0012 354
CLICK
0381 004
BARREL COMPLETE WITH
MAINSPRING
0201 083
FIRST REDUCTION WHEEL
0511 010
PAWL LEVER
0831 183
REDUCTION WHEEL HOLDER
0836 002
FOURTH WHEEL AND PINION
0144 185
29-1
29-2
*1
*1
󱣆
󱣇
󱣋
󱣌
㊲
㊳
㊴
󱣊
󱣉
󱣈
㊱

Cal. 4R37A
PARTS LIST
7/21
→Please refer to the following pages.

Lubricating: Types of oil
AO-3 (Moebius A)
SEIKO Watch Oil S-6
SEIKO Watch Oil S-4
[SETTING MECHANISM]
CENTER WHEEL BRIDGE SCREW
0012 354
CENTER WHEEL BRIDGE
0122 302
ESCAPE WHEEL AND PINION
0251 300
CENTER WHEEL AND PINION
0224 185
YOKE SPRING SCREW
0012 168
SETTING LEVER JUMPER
0388 177
YOKE
0384 183
SETTING LEVER
0383 183
CLUTCH WHEEL
0282 183
WINDING PINION
0283 020
DATE CORRECTOR
SETTING TRANSMISSION
WHEEL A
0962 183
WINDING STEM
0351 200
BALANCE STEP LEVER
0601 183
Refer to page 11 for oiling spot
MAIN PLATE
0104 182
㊸
󱣕
㊺
㊻
㊼
49
50
51
52
53
*1
*1
*2
*2
*3
*3
*4
*4
㊵
㊶
㊷
󱣙

Cal. 4R37A
PARTS LIST
8/21
REMARKS
●How to find the correct parts, if not determined by 4 digit caliber number
Following parts are determined based on the design of watches, such as hands height, dial color, and
design of cases. Please refer to the SEIKO WATCH PARTS CATALOGUE in order to choose corresponding
parts.
OSCILLATING WEIGHT 0509 ***
The type of OSCILLATING WEIGHT is determined based on the design of cases. Check the case number
and refer to the "SEIKO WATCH PARTS CATALOGUE" to choose corresponding OSCILLATING WEIGHT.
The type of DATE DIAL is determined based on the design of cases. Check the case number and refer to
the "SEIKO WATCH PARTS CATALOGUE" to choose corresponding DATE DIAL.
The type of WINDING STEM is determined based on the design of cases. Check the case number and
refer to the "SEIKO WATCH PARTS CATALOGUE" to choose corresponding WINDING STEM.
DATE DIAL 0878 ***
WINDING STEM 0351 ***
④
①
DIAL HOLDING SPACER 4408 ***
The type of DIAL HOLDING SPACER is determined based on the design of cases. Check the case number
and refer to the "SEIKO WATCH PARTS CATALOGUE" to choose corresponding DIAL HOLDING SPACER.
⑰
㊾

Cal. 4R37A
PARTS LIST
9/21
● How to discriminate resembled parts
Screws
0012354
0012168
0012485
0012919
0012420
DATE DISK GUARD SCREW (4 pcs.)
AUTOMATIC TRAIN BRIDGE (2 pcs.)
PALLET BRIDGE SCREW (2 pcs.)
LOWER PLATE FOR BARREL AND TRAIN WHEEL BRIGDE SCREW (1 pce.)
CENTER WHEEL BRIDGE SCREW (1 pce.)
②
⑱
㉕
㉟
㊵
YOKE SPRING SCREW (2 pcs.)
㊹
GUARD FOR DATE CORRECTOR SETTING TRANSMISSION WHEEL SCREW
(2 pcs.)
⑦
RATCHET WHEEL SCREW (1 pce.)
㉑
BALANCE BRIDGE SCREW (1 pce.)
BARREL AND TRAIN WHEEL BRIDGE SCREW (3 pcs.)
㉓
㉘

Cal. 4R37A
PARTS LIST
10/21
●Tools and consumables required for disassembling/reassembling
• Movement holder
 UNIVERSALMOVEMENTHOLDER(S-682)
• Watch oils
 SEIKOwatchgreaseS-6andS-4.watchoilAO-3(orMoebiusA)
S-6 AO-3
S-4

TECHNICAL GUIDE Cal. 4R37A
11/ 21
A
●
How to remove the SETTING STEM before dismantling the movement
Crown position: NORMAL
Push the A portion on the SETTING LEVER gently
(refer to the picture on the right) in order to
disengage it from the WINDING STEM.
Then pull out the crown with the stem
completely.
* After dismantling the movement from the case,
push back the crown with the WINDING STEM to
the movement.
㊼
SETTING LEVER
WINDING STEM
㊾
REMARKS ON DISASSEMBLING AND REASSEMBLING THE MOVEMENT

TECHNICAL GUIDE Cal. 4R37A
12/21
● Balance and escapement
How to disassemble/reassemble the BALANCE and BALANCE COCK
 • Disassembling
1) Rotate the STUD SUPPORT until it touches to the BALANCE COCK.
When doing so, make sure that the second bend of the balance-spring does not touch the
REGULATOR PIN.
2) Push out the stud parallel to the slit of the STUD SUPPORT (the direction also shown by the red
arrow in the illustration) in order to remove it from the STUD SUPPORT.
3) Unscrew the BALANCE COCK SCREW and remove the BALANCE COCK WITH REGULATOR.
4) Remove the BALANCE COMPLETE WITH STUD.

TECHNICAL GUIDE Cal. 4R37A
13/21
• Reassembling
1) Install the BALANCE COMPLETE WITH STUD to the MAIN PLATE.
2) Set the BALANCE COCK WITH REGULATOR and tighten the BALANCE COCK SCREW.
3) Temporarily set the stud to the STUD SUPPORT.
Do not engage the balance-spring to the REGULATOR PIN. The balance-spring passes outside of the
REGULATOR-PIN at this stage.
4) Push back the stud parallel to the slit of the STUD SUPPORT.
5) Engage the balance-spring with the slit of the REGULATOR PIN.
* When assembling the BALANCE COMPLETE, pay great
attention not to deform the balance-spring, especially at the
second bend.

TECHNICAL GUIDE Cal. 4R37A
14/21
●First reduction wheel holder
 • Disassembling  • Reassembling
●Oscillating weight
When fixing the OSCILLATING WEIGHT, an alignment with the FIRST REDUCTION WHEEL is necessary
in order to wind the MAINSPRING most efficiently. Rotate the FIRST REDUCTION WHEEL manually until
its hole aligns with the gilt dot on the BALANCE COCK and set the OSCILLATING WEIGHT vertically at
the stem side, and then tighten the screw. Refer to the figure below.
FIRST REDUCTION WHEEL
REDUCTION WHEEL HOLDER
BARREL AND TRAIN WHEEL BRIDGE (BACK SIDE)
Enlarged view
BALANCE BRIDGE GUIDE
PIN FIRST REDUCTION WHEEL
㉝
㉛
㉙
㉝

TECHNICAL GUIDE Cal. 4R37A
15/21

Lubricating: Types of oil
AO-3 (Moebius A)
SEIKO Watch Oil S-6
SEIKO Watch Oil S-4
●Barrel and train wheel bridge with hole jewel frame
Enlarged view
Back side
Enlarged view
BARREL AND TRAIN WHEEL BRIDGE WITH HOLE JEWEL FRAME
㉙
*1
*1
*2
*2
*3 *3
*4
*4
*2 After lublicating, set lower plate for barrel and train wheel bridge & screw.
LOWER PLATE FOR BARREL AND TRAIN WHEEL BRIDGE
LOWER PLATE FOR BARREL AND TRAIN WHEEL BRIDGE SCREW
㉞
㉟
After lublicating, set First reduction wheel & Pawl lever & Reduction wheel holder.
*4
FIRST REDUCTION WHEEL FIRST REDUCTION WHEEL
PAWL LEVER
REDUCTION WHEEL HOLDER
㉝
㉛
㉜
㉝

TECHNICAL GUIDE Cal. 4R37A
16/21
●Balance stop lever
Enlarged view
BALANCE STOP LEVER
MAIN PLATE Contact part of main plate and balance stop lever
●Sliding crown wheel spring
 • Disassembling  • Reassembling
Enlarged
view
Enlarged
view
PUSH
The hook of SLIDING CROWN WHEEL SPRING is
hang up a BARREL AND TRAIN WHEEL BRIDGE
WITH HOLE JEWEL FRAME.
Remove the hook of the SLIDING CROWN WHEEL
SPRING from BARREL AND TRAIN WHEEL
BRIDGE WITH HOLE JEWEL FRAME.
BARREL AND TRAIN WHEEL
BRIDGE WITH HOLE JEWEL FRAME
㉙
㉚SLIDING CROWN WHEEL
SPRING

TECHNICAL GUIDE Cal. 4R37A
17/21
●Names of the parts for regulation and their functions
STUD SUPPORT
REGUL ATOR
STUD
REGULATOR PIN
(+) side
(-) side
 • Regulator
Note:
 •Studsupport
Regulation of the accuracy rate(+) or (-)
by adjusting the operative length of the
balance-spring
Correction of the beat error by position-
ing the roller jewel correctly
• Stud(gluedatthebalance-spring)
Alignment of the balance-spring to the center of the regulator pin’s slit
• Regulatorpin
Adjustment of the play of the balance-spring embraced in its slit
Counterclockwise rotation
No clockwise rotation
REGULATION

TECHNICAL GUIDE Cal. 4R37A
18/21
●
How to regulate the isochronism fault by adjusting the position of the balance-spring
This caliber has the Etachron system for fine regulation of the isochronism fault.
When an amplitude of the balance becomes weak, the watch shows time loss, in general.
By making a clearance of the balance-spring smaller, the decline curve of the instantaneous rate gets
shallower.
1) Make sure that the REGULATOR PIN is aligned in a vertical position to the REGULATOR and the
balance-spring passes parallel through the slot of the REGULATOR PIN before fine-tuning the STUD
and the REGULATOR PIN.
REGULATOR PIN top side view back side view angled view
2) Rotate the STUD in order to align the position of the balance-spring passes through the center of the
slot of the REGULATOR PIN.
STUD REGULATOR PIN
top side view back side view
3) Rotate the REGULATOR PIN counterclockwise in order to fine-tune the clearance of the balance-
spring passing through the slot of it.
REGULATOR PIN
top side view
Before rotating After rotating
back side view
Before rotating After rotating
(Maximum clearance) (Minimum clearance)

TECHNICAL GUIDE Cal. 4R37A
19/21
REMARKS ON INSPECTION AND MEASUREMENT
Operation Function Checkpoint
Pull out the
crown to the 2nd
click and push it
back in to the
normal
position. Repeat
the same several
times.
Setting mechanism -
switching the
function of the time
setting
Make sure that it has
a click at each
position and the
stem is not pulled
off.
Pull out the
crown to the 1st
click, then turn it.
Calendar
mechanism -
correcting the date,
if available
Make sure that the
date changes
smoothly.
Pull out the
crown to the 2nd
click, then turn it.
Setting mechanism
- hour, minute and
24-hour hand setting
Make sure that the
hour and minute
hands move
smoothly (without
touching each other
or touching the
surface of the dial or
inside of the glass).
Make sure that the
24-hour hand moves
correspondingly
with the hour hand.
Hands installation
Calendar
mechanism - date
change
Make sure that the
date changes when
the hour and minute
hands pass around
midnight.
lFunction check

TECHNICAL GUIDE Cal. 4R37A
20/21
Marking on the case back Test method Applied pressure
WATER RESISTANT (WATER RESIST) 3 BAR
WATER RESIST 5BAR 5 BAR
WATER RESIST 10BAR 10 BAR
WATER RESIST 15BAR 15 BAR
WATER RESIST 20BAR 20 BAR
SCUBA DIVER'S (AIR DIVER'S) 150 m 18.75 BAR = 150 (m) times 0.125
SCUBA DIVER'S (AIR DIVER'S) 200 m 25 BAR = 200 (m) times 0.125
He-GAS DIVER'S 300 m 37.5 BAR = 300 (m) times 0.125
He-GAS DIVER'S 600 m 75 BAR = 600 (m) times 0.125
He-GAS DIVER'S 1000 m 125 BAR = 1000 (m) times 0.125
Check the water resistance according to the designated specification of the watch.
●Water resistance test
Water pressure test
Condensation test
Condensation test
Condensation test
Water pressure test
Air leak test