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PARTS CATALOGUE / TECHNICAL GUIDE
Cal. No.
Item
・3 Hands:
Hour, Minute, and 1/5 second chronograph hand
・Small Second : Small second hand(6H), Minute chronograph hand (10H),
and 24-hour indicator(2H)
Driving system
Additional function
Normal position
Crown
operation
1st click position
2nd click position Time setting, Resetting the circuit
Loss/Gain (Monthly rate)
Frequency of crystal oscillator
Operational temperature range
Regulation system
Gate time for rate measurement
Current consumption
Coil resistance
Battery No.
Power
supply
Battery voltage
Battery life
Jewels
Cal.8T68A
Step motor 2 pieces
・Stopwatch function up to 60 minutes in 1/5 second
・Date display with quick correction.
・Energy depletion forwarding function
(The second hand moves at two-second intervals.)
Free
Date setting (clockwise)
Less than 15 seconds at normal temperature range
32,768 Hz
-5℃ ~ +50℃
Nil
Use 10-second gate
・Movement: Less than 2.7μA
・Circuit block: Less than 0.7μA
・4002054（Coil block A): 1.45 - 1.65KΩ
・4002055（Coil block B): 1.65 - 1.85KΩ
SR936SW (Silver oxide battery)
1.55V
Approximately 3 years
0 jewel
1/19
8T68A
Movement Size
・Outside diameter: 30.8 mm
・Casing diameter
・Height：
29.0 mm
5.1 mm
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Summary of Contents for Seiko 8T68A
- Page 1 PARTS CATALOGUE / TECHNICAL GUIDE Cal.8T68A Cal. No. 8T68A Item Movement Size ・3 Hands: Hour, Minute, and 1/5 second chronograph hand ・Outside diameter: 30.8 mm ・Small Second : Small second hand(6H), Minute chronograph hand (10H), ・Casing diameter 29.0 mm and 24-hour indicator(2H) ・Height：...
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Page 2: Parts Catalogue
PARTS CATALOGUE 8T68A Type of oil Oil quantity mark 1 → 60 Disassembling procedures Figs. AO-3(Moebius A） NORMAL QUANTITY 60 → 1 Reassembling procedures Figs. AO-2(Moebius F) SUFFICIENT QUANTITY 0012 354 Date indicator maintaining plate screw 0808 052 Date indicator maintaining plate Date indicator Refer to page 8 for each parts code. - Page 3 PARTS CATALOGUE 8T68A 0273 042 Hour wheel 0012 354 Switch lever holder screw 0837 007 Switch lever holder 4450 018 4450 017 Switch lever B Switch lever A Refer to page 12 for Refer to page 12 for setting position.
- Page 4 PARTS CATALOGUE 8T68A 0016 121 0016 121 Switch spring screw Switch spring screw 4250 095 Switch spring Refer to page 12 for spring setting position. 0353 018 Seconds counting wheel friction spring 0190 009 Chronograph bridge 0581 007 0587 008...
- Page 5 PARTS CATALOGUE 8T68A 0016 121 0186 004 Lower plate for chronograph bridge screw Lower plate for chronograph bridge Refer to page 10 for oiling spot. 4408 149 Circuit block spacer 0125 319 4004 353 Train wheel bridge Circuit block *㉜～㊱...
- Page 6 PARTS CATALOGUE 8T68A 0231 059 4455 006 Third wheel and pinion Reset lever 0144 002 0391 028 Fourth wheel and pinion Train wheel setting lever 0261 126 Minute wheel and pinion 0281 452 0012 354 Setting wheel Coil block screw...
- Page 7 PARTS CATALOGUE 8T68A ●Tools and consumables required for disassembling/reassembling ・Movement Holder UNIVERSAL MOVEMENT HOLDER (S-682) ・Waich oils SEIKO watch oil AO-2, AO-3 and S-6 AO-2 AO-3 7/19...
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Page 8: Technical Guide
TECHNICAL GUIDE 8T68A Remarks: ● Date indicator Crown Date Color of Parts code Color of figure position position background 0878 328 4.5H Black White 0878 329 4.5H White Black * All parts code are subject to change without notice. 8/19... - Page 9 TECHNICAL GUIDE 8T68A REMARKS ON DISASSEMBLING AND REASSEMBLING THE MOVEMENT ● How to assemble chronograph wheel There is a mark on parts. Parts are set in order of the mark as shown in the table below. Image example of the mark...
- Page 10 TECHNICAL GUIDE 8T68A Type of oil Oil quantity mark AO-3(Moebius A） NORMAL QUANTITY AO-2(Moebius F) SUFFICIENT QUANTITY ● Remarks for the lubrication Hammer Note: There must be oil within the range of the arrow. Lower plate for chronograph bridge Note: : Lubricate on the pointed spot.
- Page 11 TECHNICAL GUIDE 8T68A ● How to remove the Winding Stem 1) Set the winding stem to normal position (=0). 2) Pull out the Crown with winding stem, while pushing "A" carefully. Push "A" ● How to remove or install the Battery 1) Remove the hook of the Switch Spring's Battery Clamp as illustrated in the drawing 1).
- Page 12 TECHNICAL GUIDE 8T68A 3.Spring setting position Train wheel stop lever Lower plate for chronograph bridge Hammer operating lever A Hammer Hammer operating lever B Chronograph coupling lever Setting position 4.Switch lever A and B setting position Enlarged view Switch spring...
- Page 13 ( - ) input terminal of the CIRCUIT BLOCK (please refer to “Structure of the CIRCUIT BLOCK” ). * When measuring the current consumption using the SEIKO Multi-Tester S-860, use the range of 4 μ A of SUPPLY V (= 1.55 V) & GATE TIME (2 S).
- Page 14 TECHNICAL GUIDE 8T68A 〔STRUCTURE OF THE CIRCUIT BLOCK〕 C-MOC-IC Input terminal (-) Crystal unit Input terminal Output terminal (CG) Output terminal (Hand moving) ● Value checking -coil reistance (coil block) Check the resistance of each coil block if they are within the range in the following table.
- Page 15 TECHNICAL GUIDE 8T68A DISPLAY AND CROWN / BUTTON OPERATION Note *1: Hour hand *6: 24 hour hand Crown at second position *11: *2: Minute hand Button A (START / STOP) (Time setting) *3: Chronograph second hand *8: Button B (RESET)
- Page 16 TECHNICAL GUIDE 8T68A HOW TO USE THE CHRONOGRAPH [ Standard measurement ] Press the buttons in the following order : START STOP (Finish) RESET ( 20 minutes 10 seconds ) ・Press button A to start the ・Press button A again to stop the ・Press button B to reset the...
- Page 17 TECHNICAL GUIDE 8T68A ●Water resistance test Check the water resistance according to the designated specification of the watch Marking on the case back Test method Applied pressure WATER RESISTANT(WATER RESIST) 3 BAR Air leak test WATER RESIST 5BAR 5 BAR...
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Page 18: Troubleshooting
TECHNICAL GUIDE 8T68A TROUBLESHOOTING Symptom Possible causes Solutions Movement The watch stops operating. The battery has been depleted. Measure the battery voltage. Replace the battery with a new one. The hour wheel and the pinion of Check the relevant parts, and... - Page 19 TECHNICAL GUIDE 8T68A TROUBLESHOOTING Symptom Possible causes Solutions STOPWATCH One or more STOPWATCH The relevant coil is broken. Measure the coil block resistance. hands have stopped moving Replace the coil with a new one if or show an abnormal move- necessary.