Seiko 5M42A Quick start guide

1
Movement size
The illustrations refer to Cal. 5M42A. (x 1.0)
Movement
Item
[SPECIFICATIONS]
Cal. 5M42A
Cal. 5M43A
PARTS CATALOGUE /TECHNICAL GUIDE
4.3 mmHeight
Casing diameter ø27.0 mm
Capacitor voltage: 0.5 ~ 2.3V
From 1.55V to stoppage: Approx. 168 hours
Cal. No. 5M42A 5M43A
Outside diameter ø27.6 mm
3 hands
Time indication
Step motor (Load compensated driving pulse type)
Driving system
Monthly rate at normal temperature range: less than 15 seconds
Loss/gain
NilRegulation system
Use 10-second gate.
Measuring gate by quartz tester
Automatic generating systemPower generator
Polyacene lithium condenserCapacitor
Power supply
Operating voltage range
Duration of charge
6 jewelsJewels
•Automatic generating system
•Power reserve indicator
•Overcharge prevention function
•Electronic circuit reset switch
•Train wheel setting device
•Date calendar
•Day calendar (for Cal. 5M43A only)
•Instant setting device for date calendar
•Instant setting device for day calendar (for Cal. 5M43A only)
Additional mechanism

2
Disassembling procedures Figs. : 1 →52
Reassembling procedures Figs. : 52 →1
Lubricating: Types of oil Oil quantity
Moebius A Normal quantity
SEIKO Watch Oil S-6
Ex.: Cal. 5M43A
Cal. 5M42A, 5M43A
➡➡Please see the remarks on the following pages.
PARTS CATALOGUE
0022 247
•Date dial guard screw (3 pcs.)
•Capacitor clamp screw (2 pcs.)
•Circuit block cover screw (2 pcs.)
•Oscillating weight bridge screw (2 pcs.)
•Coil block screw (1 pc.)
•Train wheel bridge screw (1 pc.)
0022 490
•Oscillating weight screw (1 pc.)
1 Hour, minute and second hands
15 0271 670
Hour wheel
Anti-magnetic shield plate
(The anti-magnetic shield plate is
welded to the main plate, and
they cannot be disassembled.)
14 0816 670
Date driving wheel
12 0962 670
Intermediate wheel for calendar correction
13 0810 660
Date jumper
11 0737 670
Day corrector setting wheel
10 Date dial
9 0808 660
Date dial guard
7 0989 660
Intermediate wheel for day correction
(Only for Cal. 5M43A)
8 0022 247
Date dial guard screw
6 Day star with dial disk
(Only for Cal. 5M43A)
5 0963 781
Snap for day star with dial disk
(Only for Cal. 5M43A)
4 0491 589
Dial washer
3 Holding ring for dial
2 Dial

3
PARTS CATALOGUE Cal. 5M42A, 5M43A
➡➡Please see the remarks on the following pages.
23 0022 247
Circuit block cover screw
33 4002 516
Coil block
32 0022 247
Coil block screw
31 4239 519
Generating stator
30 4146 518
Generating rotor
29 1002 660
Intermediate wheel for generating rotor
28 4002 519
Generating coil block
27 0198 660
Oscillating weight bridge
26 0022 247
Oscillating weight bridge screw
25 4000 731
Circuit block
24 4457 761
Circuit block cover
16 0022 490
Oscillating weight screw
17 0500 660
Oscillating weight
18 1002 662
Oscillating weight wheel
19 0022 247
Capacitor clamp screw
20 4225 518
Capacitor clamp
21 4216 509
Insulator for capacitor
22 3029 113
Capacitor unit
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







SET CODE
Rechargeable battery
3023 5MZ

4
PARTS CATALOGUE Cal. 5M42A, 5M43A
➡➡Please see the remarks on the following pages.
52 0100 659 (One-piece case type)
0100 669 (Conventional case)
Main plate
50 Winding stem
51 0221 676
Center wheel and pinion
49 0282 672
Clutch wheel
48 4239 518
Rotor stator
47 0397 660
Lever for unlocking stem
(Only for one-piece case
type)
46 0383 662
Setting lever
45 0384 661
Yoke
44 4450 730
Switch lever
43 0281 670
Setting wheel
42 0261 670
Minute wheel
41 4146 531
Step rotor
40 0701 670
Fifth wheel and pinion
39 0231 530
Third wheel and pinion
38 0241 670
Fourth wheel and pinion
37 4271 515
Capacitor connection (+)
36 0391 660
Train wheel setting lever
35 0125 660
Train wheel bridge
34 0022 247
Train wheel bridge screw

5
PARTS CATALOGUE Cal. 5M42A, 5M43A
3 Holding ring for dial
Remarks:
The type of holding ring for dial is determined based on the design of cases. Check the case number and
refer to “SEIKO Casing Parts Catalogue” to choose a corresponding holding ring for dial.
6 Day star with dial disk (Only for Cal. 5M43A)
Position of crown
and
calendar frame
0150 661 English ↔Spanish 3 o’clock Black White
LanguagePart code Color of figure Color of background
The type of day star with dial disk is determined based on the design of cases. If any other type of day
star with dial disk is required, please specify the number inscribed on the disk.
10 Date dial
The type of date dial is determined based on the design of cases. Check the case number and refer to “SEIKO
Casing Parts Catalogue” to choose a corresponding date dial.
Position of crown
and
calendar frame
Cal. No. Part code Color of figure Color of background
5M42A 0878 729 3 o’clock Black White
5M43A 0878 675 3 o’clock Black White

6
Cal. 5M42A, 5M43A
TECHNICAL GUIDE
•The explanation here is only for the particular points of Cal. 5M42A and 5M43A.
•For the repairing, checking and measuring procedures, refer to the “TECHNICAL GUIDE, GENERAL
INSTRUCTIONS”.
•How to install
Place the movement directly on the riveting plate shown in the illustration with the oscillating weight side
down, so that the oscillating weight screw is not damaged. Then, press in the hands.
C-MOS-IC
I. STRUCTURE OF THE CIRCUIT BLOCK
II. REMARKS ON DISASSEMBLING AND REASSEMBLING
1 Hands
Automatic generating input terminal
Output terminal
Crystal unit
Input terminal (–)
Input terminal (+)

7
TECHNICAL GUIDE Cal. 5M42A, 5M43A
3 Holding ring for dial
If the watch is of the one-piece case type, the movement is
fixed to the case in such a manner that the four hooking
portions of the holding ring for dial catch the case.
•How to remove
1) While pushing the lever for unlocking stem with
tweezers, pull out the winding stem.
2) Push the protrusions of the four hooking portions
toward the center of the dial with a screwdriver as
shown in the illustration to release them from the
case.
3) Insert the tip of tweezers into each of the grooves of
the holding ring for dial positioned at 1, 5 and 9
o'clock sides, and pry the ring up to remove the
movement.
•How to install
Set the movement level into the case, and push the
hooking portions of the holding ring for dial with a
screwdriver until they catch the case.
Note: Check that each of the four hooking portions
catches the case securely, and then, tighten the
eccentric posts to fix the dial.
Holding ring for dial
Casing spring
Case
Bezel
Lever for unlocking stem
Note: Two eccentric posts are used to fix the dial to the
main plate. To remove the dial, loosen them.

8
TECHNICAL GUIDE Cal. 5M42A, 5M43A
16 Oscillating weight screw
Tighten the oscillating weight screw very firmly, applying
more force than usual.
•Though the capacitor unit for Cal. 5M4 Series is of a completely different type than that for Cal. 5M2 Series,
they have a close resemblance in shape. To prevent confusion between them, the capacitor unit for Cal.
5M4 Series has two holes for discrimination on its lead terminal portion. When replacing the capacitor
unit, check for the holes to make sure you are using the proper one.
•Be sure to observe the correct polarity of the capacitor unit. The lead terminal side is the (–) side as shown
in the illustration.
•To install the capacitor unit, set the “A” portion to the hole of the main plate, and then push the “B” portion
so that it is fixed in position.
22 Capacitor unit
Note: Handle the capacitor unit with care so as not to short-circuit its (+) and (-) terminals.
24 Circuit block cover
The circuit block cover we are supplying has no calibre
number nor numeral printed on it for discriminating the
hand installation height.
Oscillating weight screw
A
B
Capacitor connection (+)
Capacitor lead terminal
Main plate
Hole for discrimination

9
TECHNICAL GUIDE Cal. 5M42A, 5M43A
26 Oscillating weight bridge screw
27 Oscillating weight bridge
•Before tightening the oscillating weight bridge screw,
check that the upper pivot of the generating rotor is
inserted properly.
•Be sure to lubricate the upper and lower pivots of the
generating rotor and intermediate wheel for generating
rotor in the quantity specified in the illustration.
Oscillating weight bridge
Generating rotor
Intermediate wheel for generating rotor
•Be sure to lubricate the ball-bearing of the oscillating
weight bridge as shown in the illustration.
29 Intermediate wheel for generating rotor
•Lubricating
Refer to the illustration at right.
35 Train wheel bridge
•Setting position
Refer to the illustrations below to check where to install the respective wheels.
Center wheel and pinion
Main plate
Third wheel and pinion
Fifth wheel and pinion
Step rotor
Fourth wheel and pinion
Fourth wheel and pinion
Fifth wheel and pinion
Step rotor
Third wheel and pinion
Setting wheel
Minute wheel

10
TECHNICAL GUIDE Cal. 5M42A, 5M43A
44 Switch lever
45 Yoke
46 Setting lever
36 Train wheel setting lever
47 Lever for unlocking stem
•Setting position and lubricating
Refer to the illustration at right.
III. VALUE CHECKING AND ADJUSTMENT
•Coil block resistance
1.7KΩ~ 2.1KΩ
•Generating coil block resistance
280Ω~ 380Ω
•Current consumption
For the whole movement : Less than 0.7µA (with voltage supplied from a battery)
For the circuit block alone : Less than 0.4µA (with voltage supplied from a battery)
Yoke
Lever for unlocking stem
(Only for one-piece case type)
Setting lever
Switch lever
Train wheel setting lever

11
TECHNICAL GUIDE Cal. 5M42A, 5M43A
•Measuring the current consumption for the whole movement
1) Connect the tester as shown in the illustration.
•Checking the automatic generating system
1) Apply the probes of the tester to the capacitor unit as shown in the illustration to measure the voltage.
Remarks:
When the current consumption exceeds the standard value for the whole movement but is within the
standard value range for the circuit block alone, the watch is generating a driving pulse to compensate
for the heavy load that may be applied to the gear train, etc.
In this case, overhaul and clean the movement parts and then measure current consumption for the
whole movement again.
Connect the tester to the input terminals (+) and (-) of the circuit block, and wait for 30 to 40 seconds before
starting measurement.
•Measuring the current consumption for the circuit block alone
2) Start the measurement 30 to 40 seconds after connecting the tester, checking that a stable measure-
ment is obtained.
3) When measuring, look through the upper hole jewel for step rotor ( ␣ A␣ in the illustration), to check that
the step rotor is rotating at one-second intervals.
Note: If a stable measurement is not obtained for the current consumption, temporarily tighten the
capacitor clamp screws at the hole B and then measure the current consumption again.
+
–
+–
+
–
S-840A
MA-40A
A
B
+–

12
TECHNICAL GUIDE Cal. 5M42A, 5M43A
Duration of charge
Number of swings
400 Approx. 2 days 10 seconds
700 Approx. 4 days 20 seconds
Quick movement of the second hand
when the power reserve indicator function
is activated
100 Approx. 6 hours 5 seconds
1,100 Approx. 7 days 30 seconds
2) Close the case back temporarily, and swing the watch from side to side approximately 100 times
rhythmically (at a rate of 2 to 3 times a second) with a snap of the wrist as shown in the illustration.
3) Remove the case back, and measure the voltage of the capacitor unit in the same manner as in step
1) above.
4) If the voltage obtained has increased more than 0.1V from the initial voltage assuming that the initial
voltage is within the range between 0.5V and 1.0V, the automatic generating system is operating
normally.
* To recheck the automatic generating system, leave the watch untouched for more than 5 minutes,
and then repeat steps 1) to 3) above.
Note: If the voltage of the capacitor unit fluctuates, the movement of the second hand may not indicate the
actual power reserve. To check the relationship between the number of swings and the duration of
charge, use the power reserve indicator more than one hour after swinging the watch the number
of times specified in the above table, and then check if the watch keeps operating for the indicated
duration of charge.
Cal. 5M42A and 5M43A are so designed that the capacitor can be charged up to 2.2V. Even if the
watch is fully charged, however, the power reserve indicator can only indicate that the capacitor
voltage is more than 1.55V, which corresponds to 7 days of duration of charge, with the second hand
showing 30 seconds of quick movement. The actual duration of charge is more than 7 days when
the watch is fully charged.
Recharging information: Number of swings required and the duration of charge until the watch stops
operating
Cal. 5M Series watches are equipped with a power reserve indicator. The current
power reserve can be checked using the second hand at the press of the button
at the 2 o’clock position.
(The table below assumes that the initial voltage of the capacitor unit is 0.5V.)
95-10 Printed in Japan