Casio SF-A7 Troubleshooting guide

R
SF-A7(LX-553A)
DC-8000(LX-553B)
FEB. 1995
(with price)
SF-A7

CONTENTS
SPECIFICATIONS ............................................................................................................1
REPLACING THE BATTERIES ........................................................................................2
TO RESET THE UNIT'S MEMORY...................................................................................2
TO SAVE THE DATA........................................................................................................3
OPERATION CHECK .......................................................................................................4
LOW BATTERY TEST ......................................................................................................6
TROUBLESHOOTING ......................................................................................................6
SCHEMATIC DIAGRAM ...................................................................................................7
EXPLODED VIEW.............................................................................................................9
PARTS LIST....................................................................................................................10

— 1 —
SPECIFICATIONS
Main Modes: Telephone Directory, Memo, Schedule, Reminder, Home Time, World Time
and Calculator.
Data storage: Storage and recall of telephone, memo, schedule, reminder data; secret
area; editing; memory status display.
Clock: Worldtime; reminder alarm; daily alarm; hourly time signal; accuracy under
normal temperatures: ±3 seconds average
Calculation: 10-digit arithmetic calculations; arithemetic constants (+, –, ×, ÷); independ-
ent memory; percentages; square roots; 20-digit approximations; other
mixed calculations
General:
Display element: 16-column ×3-line LCD
Memory capacity: 32KB (32768 bytes)
Main component: LSI
Power supply: 2 lithium batteries (CR2032)
Power consumption: 0.02 W
Battery life*: Approximately 1 year (1 hour use per day); approximately 1,800 hours
repeating one minute of input and 10 minutes of display in Telephone
Directory.
* The batteries that come installed in this unit when you purchase it are for
factory test purposes, so they will probably not provide normal service life.
Auto power off: Approximately 6 minutes after last key operation
Operating temperature: 0°C ~ 40°C (32°F ~ 104°F)
Dimensions (HWD):
Unfolded: 9.3 x 130 x 159.7 mm (3/8x 5 1/8x 6 1/4inches)
Folded: 12.4 x 130 x 82 mm (1/2x 5 1/8x 3 1/4inches)
Weight: 95.6 g (3.4 oz)

— 2 —
REPLACING THE BATTERIES
1. Loosen the screw on the back of the unit that holds the battery
compartment cover in place, and remove the cover by sliding
it to the direction indicated by the arrow.
2. Loosen the screw that secures one of the two battery holders
in place and remove the battery holder.
Caution: Be sure to remove only one battery at a time.
Otherwise, you will lose all data stored in memory.
3. Replace the old battery with a new one, making sure that the
positive (+) side of the new battery is facing up (so you can
see it).
4. Replace the battery holder and secure it by tightening its screw.
•Be careful that you do not overtighten the screw.
5. Repeat Steps 2 through 4 for the other battery.
•Be sure to replace both batteries. Never mix old batteries
with new ones, and be sure to use CR2032 lithium batteries
only.
6. After you replace both batteries, replace the battery compart-
ment cover and secure it by tightening its screw.
•Be careful that you do not overtighten the screw.
TO RESET THE UNIT'S MEMORY
Warning!
The following procedure erases all data stored in the memory of the unit. Perform the following operation
only when you want to delete all data and initialize the settings of the unit.
Remember — you should always keep copies of important data by writing it down.
1. Switch on power and press the RESET button with a thin, pointed object.
Warning!
The next step deletes all data stored in the unit's memory. Make sure that you really want to delete the data
before you continue!
RESET button

— 3 —
TO SAVE THE DATA
The unit can transfer the data stored to another unit.
CAUTION: Before connecting wires, be sure to put the units in transmission and receiving mode.
Furthermore, after completing saving data, remove wires while showing OK or NG on display. If no, data
stored in customer's unit are corrupted.
To save the data, the following steps must be followed;
1. Remove the battery cover of both units.
2. Press RESET button of both units.
3. Short the pad TR of customer's unit. (Display shows "T".)
4. Short the pad TR twice of slave unit. (Display shows "R".)
5. Connect 4 terminals on PCB with wires as shown in the figure below.
Home Time: 12-hour format
JAN/1/1995
AM/12:00 00
Zone: Tokyo (TYO)
World Time: London (LON)
Daily Alarm: 12:00 AM
Sound: Reminder alarm →OFF
Daily alarm →OFF
Key input tone →OFF
Hourly time signal →OFF
2. Press EXE to reset the memory and delete all data or any other key to abort the reset operation without
deleting anything.
Following the reset operation described above, the Home Time display appears and the unit settings are
initialized as noted below.
CP10
CP11
CP13
CP2
CP10
CP11
CP12
CP2
CP12
TR CP2
CP11
CP13
CP10
Customers Slave
Enlarge Enlarge
RESET button RESET button

— 4 —
6. Press SET key of customer's unit. (No display)
7. Press SET key of slave unit. (No display) (Saving data is completed, the display shows OK.)
8. Remove 4 wires while showing OK on display.
9. If the display shows NG, execute the above operation from 2.
OPERATION CHECK
No.
1
2
3
4
5
6
OPERATION
RESET
EXE
(SEARCH) 3, 4 times
TEST pad
TEST pad
TEST pad
DISPLAY
RESET?
1TEL 2SCHD 3REM
4SEC 5TIME 6ALM
7 MEMO 8CAL
MENU
1TEL 2SCHD 3REM
4SEC 5TIME 6ALM
7 MEMO 8CAL
MENU
All dots
Vertical stripes.
Vertical stripes.
NOTE
RESET
Contrast adjustment
Confirm display and high-pitched
buzzer sound.
Confirmdisplayand alarmsound.
Confirm display and low-pitched
buzzer sound.
Bottom View
Enlarge
RESET button
TEST pad
Batteries

— 5—
DISPLAY
No display
= OK =
ALPHA
= NG =
ALPHA
NAME?
ALPHA
ASDFGHJKLZXCVBNM
TEL 23456
FAX 7890!
ALPHA
_FGHJKLZXCVBNM
TEL 23456
FAX 7890!
ALPHA
◆CAPACITY◆0%
USED 0
FREE 32768
ALPHA
No display
RESET?
1TEL 2SCHD 3REM
4SEC 5TIME 6ALM
7 MEMO 8CAL
MENU
NO.
7
8
9
10
11
12
13
14
15
OPERATION
TEST pad
TEST pad
(Takes 5 min.)
ON 1
A S D F G H J K
L Z X C V B N M EXE
2 3 4 5 6 EXE 7 8
9 0 SYMBOL
EXE EXE (SEARCH)
EDIT DEL DEL INS SPACE
CLEAR A EXE CAPA
OFF
ON
RESET
EXE
NOTE
USER MODE (TEL)
RESET

— 6 —
NO.
16
OPERATION
(SEARCH) , 3 times
DISPLAY
1TEL 2SCHD 3REM
4SEC 5TIME 6ALM
7 MEMO 8CAL
MENU
NOTE
LOW BATTERY TEST
NO.
1
2
OPERATION
ON
OFF
NOTE
VDD is 5.07V or below.
DISPLAY
LOW BATTERY !
MENU
TROUBLESHOOTING
CAUSE
Battery shortage
Poor contact of battery terminals
Defective TAB-LSI
Poor contact SW1
Poor soldering of power supply circuit
Defective PCB unit
Defective TAB LSI
Defective heat seal
Defective LCD
Poor soldering of power supply circuit
SOLUTION
Replace batteries
Replace or polish them
Replace it
Replace it
Resolder them
Replace it
Replace it
Replace it
Replace it
Resolder it
SYMPTOM
No power
No display or wrong display

— 7 —
SCHEMATIC DIAGRAM
Main PCB (1/2)

— 8 —
Main PCB (2/2)

1
I
J
K
L
M
N
O
H
P
Q
R
S
T
U
2
3
4
5
6
7
8
A
B
0
D
E
F
G
9
C
— 9 —
EXPLODED VIEW

PARTS LIST FOB Japan
N Item Code No. Parts Name Specification Q'ty M N.R.Yen R
AT BT Unit Price
PCB ASS'Y
N 5 5610 8580 Heat seal FX200P50302 11 5 80 C
N 6 3335 5488 LCD CD426-TS 11 1 260 A
N 7 6414 5410 Sponge cushion FH100030001 2220 5 X
N 11 6414 5420 Spacer EL000L98109 1120 5 X
12 6410 0830 Blind tape L180 A414656-1 1120 10 X
20 6403 9330 Tape C-L170 A413108-1 1120 6 X
22 6409 6300 Battery plate (+) EF01DB20102 2220 16 X
23 6409 6310 Battery plate (-) EF02DB10100 2220 16 X
C1,C15,C18 2803 6806 Capacitor 10MS510M-MW 3320 13 C
N C11,C13 6414 5530 Chip capacitor CP018C612T1 2220 11 C
N C16 6054 3080 Chip capacitor CP001B612T7 1120 16 C
N C17 6414 5500 Chip capacitor CP120F602T6 1120 11 C
C2,C3 6511 7510 Chip capacitor CP018F602A7 2220 11 C
C4,C5 6511 7520 Chip capacitor CP030F602T7 2220 11 C
C6,CB1,CB2 6511 7560 Chip capacitor CP001A432T8 7720 7 C
C7~C10
D1 2390 2135 Diode BC20MA740T0 11 5 50 C
N D2 6414 5510 Diode BC1SB007BT8 1110 30 C
D3,D4 2315 0212 Chip diode MA153-(TX) 2210 33 C
IC2 2105 3297 IC S-80752AN-JG-T1 1110 47 C
IC6 2105 1568 IC TC7S32F-TE85R 1120 27 B
N LSI1 6413 1460 COF3008-F1 sub ass'y A340092*1 11 1 670 A
LSI2 2011 3955 LSI uPD43256BGU-B12 11 1 690 B
R1,R2 6512 1360 Chip resistor CC0012D11T6 2220 3 C
R3 6512 1440 Chip resistor CC0016D11T4 1120 3 C
N R4 6414 5520 Chip resistor CC2003D11T1 1120 3 C
N R5 6414 5490 Chip resistor CC0562D11T8 1120 3 C
N R6 6414 5480 Chip resistor CC0470D11T0 1120 3 C
X1 6510 4550 Crystal BD0063P2509 11 5 55 X
X2 6414 5460 Ceramic oscillator BD0078P4605 11 5 80 C
COMPONENT
N 1 6414 5670 Hard case FC10L981016 01 5 80 X
N 1 6414 5270 Hard case FC10L981008 10 5 80 X
N 2 6414 5660 Operation label HGF00004009 0110 30 X
N 2 6414 5260 Operation label HGF00003509 1010 30 X
N 3 6414 5380 Display plate EL5F0016106 10 5 70 X
N 3 6414 5630 Display plate EL5F0016203 01 5 70 X
4 6410 9670 Push button FB3DB100001 10 1 130 X
N 4 6414 5600 Push button FB3DB100108 01 1 130 X
N 8 6414 5330 Screw MAB20103201 3320 3 X
N 9 6414 5310 PCB ass'y L98XXX0300V*1 11 1 2,070 B
10 3122 2380 Buzzer EFB-S55C41A8 1110 36 X
13 6408 5920 SW knob ass'y DB2AXX4A00M 1110 30 B
N 14 6414 5640 Lower cabinet FAB0L981013 0110 40 X
N 14 6414 5230 Lower cabinet FAB0L981005 1010 40 X
N 15 6414 5250 Battery cover label HGF00003606 1120 10 X
N 16 6414 5650 Battery cover FAD0L981010 0110 30 C
N 16 6414 5240 Battery cover FAD0L981001 1010 30 C
N 17 6414 5390 Screw MAA90004302 1120 3 X
N 18 6414 5350 Upper cabinet FAA0L981009 10 1 120 X
Notes: N – New parts R – A : Essential
M – Minimum order/supply quantity B : Stock recommended
R – Rank C : Others
Q – Quantity used per unit X : No stock recommended
AT :
BT : SF-A7 DC-8000
— 10 —

FOB Japan
N Item Code No. Parts Name Specification Q'ty M N.R.Yen R
AT BT Unit Price
N 18 6414 5620 Upper cabinet FAA0L981017 01 1 120 X
N 19 6414 5320 Rubber sheet LAOL9810001 10 1 250 X
N 19 6414 5610 Rubber sheet LA0L9810108 01 1 250 X
21 6510 4500 Buzzer tape HGFC0000501 1120 17 X
24 6510 4440 Insulation seal HGFC0001206 3320 6 X
N 25 6414 5370 Overlay mylar EL4F0007105 1120 10 X
26 6512 1080 Nut MD100000602 3320 13 X
27 6511 8400 Key contact rubber LADB0220105 1120 10 X
N 28 6414 5340 Screw MAB20106307 5520 3 X
29 6409 6120 Battery holder ECDB1011108 1120 26 X
30 6409 6210 Battery change label HGC00001102 1120 7 X
31 6512 0990 Screw MAA80006329 2220 3 X
Notes: N – New parts R – A : Essential
M – Minimum order/supply quantity B : Stock recommended
R – Rank C : Others
Q – Quantity used per unit X : No stock recommended
— 11 —

MA0500751A