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)