Seiko 8R48A Quick start guide

Movement
[Bridge side] [Calendar side]
Cal. 8R48A Cal. 8R49A
PARTS LIST/TECHNICALGUIDE
Automatic Chronograph Cal. 8R48A/8R49A
[SPECIFICATIONS]
1/24
Item Cal. No. 8R48A/8R49A
34 jewels
Automatic winding with manual winding mechanism
+ 25 / - 15 seconds at normal temperature range
(Between 5°C and 35°C )
• Stopwatch function
Measures up to 12 hours
• Semi-instantaneous date change mechanism
• Second hand stop function
Date setting (counterclockwise only)
Time setting (Hour and minute)
Manual winding (clockwise only)
• Diameter Outside: Ø 28.6 mm
Casing: Ø 28.0 mm
• Height:  7.62 mm
• 3 hands (hour and minute hands, and small second hand at
3 o'clock position)
• Calendar (Date: Date disk)
28,800 (8 beats per second)
Testing
positions
± 10 s/d
Measurement
(daily rate in
seconds:s/d)
Dial upward
+ 20 s/d
– 10 s/d
ETACHRON system
From fully wound to stoppage: Approximately 45 hours
Movement size
52 °
6 o’clock
at the top up Dial upward
9 o’clock
at the top up
Isochronous fault
Instantaneous rate at T0
(Fully wound condition)
+ 15 s/d
– 5 s/d + 20 s/d
– 10 s/d
Driving system
Additional function
Crown operation
Daily Date
Regulation system
Number of jewels
Normal position
1st click position
2nd click position
Lift angle of the escapment
Vibration per hour
Coutinuous operating time
Standard rate
for movement
Loss/Gain

SPECIFICATIONS
2/24
Cal. 8R48A/8R49A
Disassembling procedures figs. 1 93
Reassembling procedures Figs. 93 1
Types of oil Oil quantity mark
AO-3 (Moebius A) NORMAL QUANTITY
S-6
S-4 SUFFICIENT QUANTITY
[ NOTE ]
Please press button A to START the chronograph function before disassembly.
If it is at RESET position 41 Chronograph coupling lever A and 42 Chronograph coupling lever B are
under 47 Second counting intermediate wheel; it makes disassembly difficult.
Button B
Chronograph RESET
Button A
Chronograph START / STOP
1 0509 ***
Oscillating weight with ball bearing
*Refer to page 10 for the parts code
*1
*1

PARTS CATALOGUE Cal. 8R48A/8R49A
3/24
*1
2 0016 709
Hour wheel guard screw
*3
3 0376 178
Hour wheel guard
4 0491 184
Dial washer A
5 0273 277
Hour wheel
7 0016 709
Date indicator maintaining plate screw
8 0808 178
Date indicator maintaining plate
10 0810 177
Date jumper
13 0595 177
Date corrector lever
14 0732 177
Date corrector cam
17 0012 092
Chronograph bridge screw
18 0190 ***
Chronograph bridge
* Refer to page 15 for the oiling
position.
* Refer to page 10 for the parts
code
17 0012 092
Chronograph bridge screw
16 0353 177
Second counting sheel spring
15 0012 092
Second counting wheel spring screw
12 0817 179
Intermediate date wheel and pinion
11 0802 178
Date indicator driving wheel
9 Date dial
6 0270 443
Center wheel
Intermediate date wheel
and pinion setting position
*5
*2
*4
*5
*2
*3
*1
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4
Oiling position
Second counting wheel spring
Second counting wheel *4

Cal. 8R48A/8R49A
PARTS CATALOGUE
4/24
19 0491 182
Dial washer C
22 0886 183
Minute counter intermediate
wheel and pinion B
24 0902 ***
Minute counting wheel
* Refer to page 11 for
location of jewels.
20 0491 181
Dial washer B
Note:
Refer to the page 19 for distinguishing
the dial washers B, C and D.
21 0491 183
Dial washer D
23 0886 182
Minute counter intermediate
wheel and pinion A
25 0902 ***
Hour counting wheel
* Refer to page 11 for location of
jewels.
27 0894 177
Wheel stop lever
28 0587 179
Hammer operating lever B
26 0743 179
Hour chronograph coupling lever
* Refer to page 12 for the oiling
position.
30 0587 181
Hammer operating lever A
29 0782 177
Click spring
* Refer to page 12 for the oiling
position.
31 0585 177
Hammer
* Refer to page 14 for
the oiling position.
Note:
For the setting position of the spring
and lever etc., refer to page 16.
*2
*1*1
*2
*1
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4

34 0575 177
Operating lever spring
35 0571 179
Operating lever B
40 0837 178
Chronograph coupling lever holder
41 0581 179
Chronograph coupling lever A
PARTS CATALOGUE Cal. 8R48A/8R49A
5/24
*1
*2
*1
*2
Note:
For the setting position of the spring
and lever etc., refer to page 16.
44 0240 ***
Second wheel
* Refer to page 10 for the parts
code.
42 0581 180
Chronograph coupling lever B
32 0571 177
Operating lever A
33 0012 092
Operating lever spring screw
45 0012 201
Operating cam screw
46 0576 180
Operating cam
* Refer to page 14 for the oiling
position.
47 0885 192
Second counter intermediate
wheel
36 0012 092
Operating cam jumper screw
37 1024 177
Operating cam jumper
38 0012 092
Chronograph coupling lever
spring screw
39 0584 178
Chronograph coupling
lever spring
43 0888 181
Second counting wheel
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4

Cal. 8R48A/8R49A
PARTS CATALOGUE
6/24
*1
48 0186 192
Chronograph main plate
* Refer to page 15 for the
oiling position.
49 0012 354
Unit intermeidate spacer
screw
50 4408 181
Unit intermediate spacer
51 0962 023
Date corrector setting
transmission wheel D
52 0962 023
Date corrector setting
transmission wheel C
53 0962 190
Date corrector setting
transmission wheel B
54 0817 180
Time setting transmission
wheel and pinion
55 0505 181
Second transmission wheel
* Refer to page 17 for the
setting position.
56 0505 182
Minutes transmission wheel
* Refer to page 14 for the
oiling position.
* Refer to page 17 for the
setting position.
57 Main plate
58 0012 092
Main plate screw
58 0012 092
Main plate screw
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4
*1

59 0012 420
Balance bridge screw
60 0171 349
Balance cock
60-1 0310 ***
Balance complete with stud
* Refer to page 10 for the parts code.
61 0012 354
Pallet bridge screw
62 0161 310
Pallet bridge
63 0301 315
Pallet fork
PARTS CATALOGUE Cal. 8R48A/8R49A
7/24
*1
*1
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4

Cal. 8R48A/8R49A
PARTS CATALOGUE
8/24
64 0012 354
Automatic train bridge screw
65 0191 064
Automatic train bridge
66 0514 183
Second reduction whell and pinion
67 0012 919
Ratchet wheel screw
68 0285 051
Ratchet wheel
74 0511 010
First reduction whell and arbor
73 0831 183
Pawl lever
72 0836 002
Reduction wheel holder
69 0012 420
Barrel and train wheel
bridge screw
71 0363 184
Ratchet sliding wheel
spring
76 0436 166
Lower plate for barrel
and train wheel bridge
75 0012 354
Lower plate for barrel
and train wheel bridge
screw
70 0114 177
Barrel and train wheel bridge
* Refer to page 13 for the
oiling position.
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4

Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4
PARTS CATALOGUE Cal. 8R48A/8R49A
9/24
*1
*2
*4
*3
77 0144 178
Fourth wheel and pinion
78 0231 070
Third wheel and pinion
79 0012 354
Center wheel bridge screw
80 0122 302
Center wheel bridge
81 0221 178
Center wheel and pinion
82 0381 004
Click
83 0201 178
Barrel complete with mainspring
85 0012 168
Yoke spring screw
86 0388 177
Yoke spring
84 0251 314
Escape wheel and pinion
87 0384 183
Yoke
89 0601 310
Balance stop lever
90 0351 200
Winding stem
93 0962 183
Date corrector setting
transmission wheel A
92 0283 020
Winding pinion
88 0383 185
Setting lever
91 0282 183
Clutch wheel
*2
*1
*3
*4

Cal. 8R48A/8R49A
PARTS CATALOGUE
10/24
● List of screw
Parts code Parts name Parts code Parts name Parts code Parts name
0012 092 Second counting wheel
spring screw
0012 354 Unit intermediate
spacer screw
0012 420 Balance bridge
screw
Chronograph bridge
screw (x5)
Pallet bridge screw
(x2)
Barrel and train
wheel bridge
screw (x3)
Operation lever spring
screw Automatic train
bridge screw (x2)
0012 168
Yoke spring screw
(x2)
Operation cam jumper
screw
Lower plate for barrel
and train wheel bridge
screw
Chronograph coupling
lever spring screw
Center wheel bridge
screw
Main plate screw (x4) 0012 201
Operatig cam screw
0016 709 Hour wheel guard
screw (x3)
0012 919
Ratchet wheel screw
Date indicator
maintaining plate
screw
59
69
85
45
79
75
64
61
49
15
17
33
36
38
58
67
2
7
Date dial
9
Parts code Position of crown Position of date
frame Color of numbers Color of background
0878 109 3H 3H Black Silver
(Plain metal)
0878 108 3H 3H White Black
● How to find the correct parts, if not determined by 4 digit caliber number
*All parts code are subject to change without notice.
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 with ball bearing 0509 *** • 1509 ***
DATE DISK 0878 ***
WINDING STEM 0351200
*For screw down crown models, the stem is assembled to the crown and is not available separately.
1
9
90
CAL Hand Height 18 Chronograph
bridge
19 Minute counting wheel
20 Hour counting wheel
44 Seconds
wheel
60-1 Balance
complete without
stud
8R48 3 (LONG) 0190192 0902184 0240178 0310055
4 (SPECIAL) 0190193 0902191 0240191
8R49 3 (LONG) 0190192 0902184 0240178 0310277
18 Chronograph bridge 0190 ***
24 Minute counting wheel 0902 ***
25 Hour counting wheel 0902 ***
44 Seconds wheel 0240 ***
60 -1 Balance complete without stud 0310 ***

● Location of the jewels
Upper Lower
Cap jewel Hole jewel Cap jewel Hole jewel
77 FORTH WHEEL -○- -
78 THIRD WHEEL
○ ○ -○
84 ESCAPE WHEEL ○ ○ -○
81 CENTER WHEEL
-○-○
66 2ND REDUCTION WHEEL -○-○
-○- -
74 1ST REDUCTION WHEEL -○-○
12 INTERMEDIATE DATE WHEEL
-○- -
22 MINUTE COUNTING 2ND
INTERMEDIATE WHEEL
-○-○
23 MINUTE COUNTING 1ST
INTERMEDIATE WHEEL -○-○
25 HOUR COUNTING WHEEL
---○
24 MINUTE COUNTING WHEEL
---○
43 SECONDS COUNTING WHEEL
- - - -
44 SECONDS WHEEL
---○
47 CHRONOGRAPH WHEEL -○-○
60
BALANCE COMPLETE (WITH STUD)
○○○○
63 PALLET FORK
-○-○
ENTRY PALLET JEWEL ○
EXIT PALLET JEWEL ○
ROLLER JEWELS ○
TOTAL NUMBER OF JEWELS 34 jewels
BALANCE AND
ESCAPEMENT
GEAR TRAIN
MECHANISM
WINDING
MECHANISM
CHRONOGRAPH
UNIT
CROWN WHEEL (Assembled to the
BARREL AND TRAIN WHEEL BRIDGE
70
PARTS CATALOGUE Cal. 8R48A/8R49A
11/ 24

• 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
Cal. 8R48A/8R49A
PARTS CATALOGUE
12/24
●Tools and consumables required for disassembling/reassembling

1. Oiling spot
TECHNICAL GUIDE Cal. 8R48A/8R49A
13/24
■Note 1:
(1) 70 Barrel and train wheel bridge with hole jewel frame
70 Barrel and train wheel bridge with hole jewel frame (back side)
After oiling *2, set lower plate for barrel and train wheel bridge & screw.
76 Lower plate for barrel and train wheel bridge
75 Lower plate for barrel and train wheel bridge screw
And then, set first reduction wheel, pawl lever & reduction wheel holder.
*1
*1
*4 *3
*2
74 First reduction wheel
73 Pawl lever
72 Reduction wheel holder
74 First reduction wheel
■Note 2:
Refer to page 18 for disassembling and reassembling of the first reduction wheel.
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4
*4 *3
*2

37 Operating cam jumper
28 Hammer operating lever B
29 Click spring
31 Hammer
26 Hour chronograph coupling lever
1. Oiling spot
(2) 46 Operating cam (3) 31 Hammer
(4) 26 Hour chronograph coupling lever
Back side
(5) 29 Click spring
(6) 56 Minutes transmission wheel
TECHNICAL GUIDE Cal. 8R48A/8R49A
14/24
30 Hammer operating lever A
37 Operating cam jumper
29 Click spring
31 Hammer
*1
*2
*2
*1
Note :
Make sure to libricate on whole teeth.
Note :
There must be oil within the range of the arrow.
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4

1. Oiling spot
(7) 48 Chronograph main plate
(8) 18 Chronograph bridge
[ Dial side ] [ Back side ]
Turn the gear after oiling
TECHNICAL GUIDE Cal. 8R48A/8R49A
15/24
*3
*1
*2
*4
Note :
There must be oil within the range of the arrow.
*1 *2
*3
*4
Types of oil
AO-3 (Moebius A)
Oil quantity mark
NORMAL QUANTITY
SUFFICIENT QUANTITY
S-6
S-4

29
26
27
46
35
40
41
30
37
46
35
27
30
37
46
26
TECHNICAL GUIDE Cal. 8R48A/8R49A
16/24
35 Operating lever B
2. The setting position of the spring and lever etc.
30 Hammer operating lever A
46 Operating cam
41 Chronograph couling lever A
27 Wheel stop lever
28 Hammer operating lever B
37 Operating cam jumper
29 Click spring
31 Hammer
34 Operating lever spring
32 Operating lever A
40 Chronograph coupling
lever holder
42 Chronograph coupling
lever B
39 Chronograph coupling
lever spring
26 Hour chronograph coupling lever
Note :
After assembling the movement, if an operation with the button does not work successfully, please recheck the
spring position.
42
39
35
34
30
29
37
28
31
The setting position of the operation cam with and lever.
※48 Chronograph main plate
※
*1 *2 *3 *4
*5 *6
*2
*1 *5
*4
*3
*6

Hour and minute counting wheel need to be inclined when setting.
• Second transmission wheel and minute transmission wheel should be set parallel to main plate.
• Once the second transmission wheel and minute transmission wheel are detached, be sure to replace them
with new ones instead of reusing them.
56 Minute transmission wheel
81 Center wheel and pinion
Second transmission wheel Fourth wheel and pinion
*1 *2
*2
*1
Minute transmission wheel Center wheel and pinion
Set chronograph coupling lever A and chronograph coupling lever B
as illustrated.
TECHNICAL GUIDE Cal. 8R48A/8R49A
17/24
3. Chronograph coupling A and B setting position
42 Chronograph coupling lever B
4. Hour chronograph coupling lever setting position
41 Chronograph coupling lever A
5. Second transmission wheel and minute transmission wheel setting position.
47 Second counting intermediate wheel
• Make sure to parallel with the main plate. • The second transmision wheel top surface
should be set parallel with the fourth
wheel and pinion tip.
25 Hour counting wheel
24 Minute counting wheel
26 Hour chronograph coupling lever
77 Fourth wheel and pinion
55 Second transmission wheel

Remove the hook of Ratchet sliding wheel spring from
Barrel and train wheel bridge with hole jewel frame.
<< Disassembling >>
6. Disassembling / Reassembling of the first reduction wheel
The hook of Ratchet sliding wheel spring are hung up on
Barrel and train wheel bridge with hole jewel frame.
<< Reassembling >>
<< Disassembling >> << Reassembling >>
7. Disassembling / Reassembling of the ratchet sliding wheel spring.
PUSH
TECHNICAL GUIDE Cal. 8R48A/8R49A
18/24
74 First reduction wheel
74 First reduction wheel
72 Reduction wheel holder
70 Barrel and train wheel bridge (back side)
71 Ratchet sliding wheel spring
70 Barrel and train wheel bridge with hole jewel frame

Detach and reassemble the chronograph unit and base unit by taking off the screws (4pcs.)
8. Chronograph unit and Base unit (Disassembling and Reassembling)
Note:
Before attaching the chronograph unit, check that base unit operates correctly.
When attaching chronograph unit on base unit, push button A for the START function, in order to ensure that
the following wheels mesh perfectly with one another.
9. Identification and setting position of Dial washers
TECHNICAL GUIDE Cal. 8R48A/8R49A
19/24
55 Main plate screw
58 Main plate screw
Chronograph unit
Base unit
Crown position Base unit Chronograph unit Check point
First click position Date corrector setting
transmission wheel D
Date corrector setting
transmission wheel E Date correction
Second click position
Minutes transission
wheel Minute wheel pinion A Hand setting
Seconds transmission
wheel
Seconds counter
intermediate wheel Hand driving
55
51
56
Parts code Parts code Set position Note
Dial washer B
(2 pcs) 0491 181
Minute counting
wheel
Hour counting wheel
• Color of Brass
Do not set it upside down
Dial washer C 0491 182
Minute counter
intermediate wheel
and pinion B
• Color of Silver
Dial washer D 0491 183 Second wheel • Color of Brass
20
19
21

10. Accuracy adjustment
Note:
Adjustment of each part is as follows;
• Regulator ... Time adjustment • Stud support ... Beat error adjustment
• Regulator pin ... Isochronous fault adjustment
Anticlockwise rotation Clockwise rotation
TECHNICAL GUIDE Cal. 8R48A/8R49A
20/24
Regulator
Stud support
Regulator pin
(+) side
(–) side