Casio DC-7800RS Troubleshooting guide

DC-7800RS(ZX-725)
DC-8500RS(ZX-726)
JAN. 1997
R
(without price)

CONTENTS
SPECIFICATIONS .............................................................................................................. 1
OPERATION CHECK ......................................................................................................... 2
DATA TRANSFER.............................................................................................................. 3
TROUBLESHOOTING........................................................................................................ 4
SCHEMATIC DIAGRAMS .................................................................................................. 5
PARTS LIST ....................................................................................................................... 7
EXPLODED VIEW .............................................................................................................. 8

— 1 —
SPECIFICATIONS
Display: Liquid crystal display
Power supply: Two lithium batteries (CR2032)
Power consumption: 0.1 W
Current consumption: DC-7800RS When AC key is pressed; Max. 18.7 µA. Typ. 9.5 µA
While Power OFF; Max. 14.7 µA
While buzzing; Max. 765 µA
When backlighting; Max. 16,500 µA
DC-8500RS When AC key is pressed; Max. 20.7 µA. Typ. 10.5 µA
While Power OFF; Max. 16.7 µA
While buzzing; Max. 767 µA
When backlighting; Max. 16,500 µA
Battery life: Approx. 1 year (one hour operation per day with two backlight opera-
tions and one daily alarm operation)
Auto power off: Approx. 6 minutes after last key operation
Ambient temperature range: 0 °C ~ 40 °C (32 °F ~ 104 °F)
Dimensions: 15.3 (H) ×134 (W) ×92 (D) mm .........Folded
(5/8" (H) ×5 1/4" (W) ×3 5/8" (D))
10.9 (H) ×134 (W) ×180 (D) mm .......Unfolded
(3/8" (H) ×5 1/4" (W) ×7 1/8" (D))
Weight: DC-7800RS; 121.5 g (4.3 oz)/DC-8500RS; 122 g (4.3 oz) including
batteries

— 2 —
OPERATION CHECK
Note: Before performing the operation, save the data to another unit referring “DATA TRANSFER”
on page 3.
MODE
No.
1
2
3
4
5
KEY
While pushing down the RE-
SET button, press Gthen
release the RESET button.
Press for about 1 sec-
ond.
Press for about 1 sec-
ond.
Press for about 1 sec-
ond.
DC-8500RS: Press for
about 1 sec-
ond.
DC-7800RS: Press RESET
button.
DISPLAY NOTE
The unit emits a buzz.
RESETbuttonislocated
on the back of the unit.
If the unit is faulty, LCD
indicates “NG” instead
of “OK”.
DC-7800RS
DC-8500RS

— 3 —
SCLK_
GNDSOUT
SIN
DATA TRANSFER
The DC-7800RS/8500RS can transfer the stored data to another DC-7800RS/8500RS.
Note: Before connecting wires, be sure to reset the Back up unit.
1. Remove the BATT 2 battery cover.
2. Connect 4 terminals on the PCB with wires as shown in the figure below.
User's unit Back up unit
RESET
BATT 1
BATT 2
RESET
BATT 1
BATT 2
Wiring
GND GND
SCLK_ SCLK_
SIN SIN
SOUT SOUT

— 4 —
Note: Perform the operation in numerical order.
User's unit Back up unit
Operation
1WhilepushingdownRESET
button, press Ethen re-
lease RESET button.
4Press .
5After the data transmis-
sion....
It takes a few minutes to
complete the data transfer.
7Press RESET button.
9Press .
Note: Never press as it
deletes all the data.
APress (OFF).
Operation
2WhilepushingdownRESET
button, press Fthen re-
lease RESET button.
3Press .
6Whenthedataistransferred
properly......
In case the data transfer
ends incomplete......
8Press RESET button.
0Press .
Note: Never press as it
deletes all the data.
BPress (OFF).
TROUBLESHOOTING
Before doing the following solutions, save data if possible.
SYMPTOM SOLUTIONCAUSE
No power Weak battery Replace batteries
ResolderPoor soldering of the power
supply circuit
No display at all or wrong display Defective heat seal Replace the heat seal
Defective LCD Replace the LCD
Display
R?
(Unit emits a buzz.)
R?
(Unit emits a buzz.)
END
NG!
or
USED FREE
5250 60220
The above example
is DC-8500RS dis-
play. The numbers
vary depending on
the quantity of data.
Display
T?
(Unit emits a buzz.)
T?
(Unit emits a buzz.)
END
USED FREE
5250 60220
The above example
is DC-8500RS dis-
play. The numbers
vary depending on
the quantity of data.

— 5 —
SCHEMATIC DIAGRAMS
Main block

— 6 —
Key block

PARTS LIST
N Item Code No. Parts Name Specification Version Q R
PCB ASS'Y
N IC1 2105 6304 DETECTOR RH5VT54AA-T1  Common 1 B
IC2 2105 5894 REGULATOR RH5RL33AA-T1  Common 1 B
IC3 2011 3955 LSI uPD43256BGU-B12 Common 1 B
IC4 2011 3955 LSI uPD43256BGU-B12 DC-8500RS 1 B
IC5 2114 5747 IC ABD353X0000  Common 1 B
D1 6510 4940 DIODE BC10MA71307  Common 1 B
D2~5 2390 1442 CHIP DIODE MA152K-(TX)  Common 4 B
L1 3013 2471 CHIP INDUCTORS ELT5K114C  Common 1 B
X1 6510 4550 CRYSTAL BD0063P2509 (DT-26S)  Common 1 B
N 1 3335 6537 LCD AC10CD44105 Common 1 A
2 6419 2230 HOT MELT FILM FX200P50604  Common 1 A
N 3 6419 8060 PCB ASS’Y DB39XX0300R*1 DC-7800RS 1 B
N 3 6419 8070 PCB ASS’Y DB39AX0300L*1 DC-8500RS 1 B
The PCB ASS'Y contains the above elements and COB LSI.
COMPONENT
4 6418 1080 EL PANEL Z723 A341294-1  Common 1 B
N 5 6419 8180 BATT COVER FADOL961051 Common 2 C
6 6419 1820 PUSH BUTTON FB3DB371004  Common 1 X
N 7 6419 8150 UPPER CABINET FAADB391001 DC-7800RS 1 X
N 7 6419 8160 UPPER CABINET FAADB391010 DC-8500RS 1 X
N 8 6419 8170 RUBBER SHEET LADB3910005 Common 1 X
N 9 6419 8210 SPONGE FH100040601 Common 1 C
N 10 6419 8220 HARD CASE FC1DB371042 DC-7800RS 1 X
N 10 6419 8230 HARD CASE FC1DB371051 DC-8500RS 1 X
N 11 6419 8240 OPERATION LABEL HGL00006103 DC-7800RS 1 X
N 11 6419 8250 OPERATION LABEL HGL00006201 DC-8500RS 1 X
N 12 3122 3513 BUZZER CK225P30024 Common 1 X
13 6408 5830 RB SHEET LADB0140101  Common 1 X
N 14 6419 8260 LOWER CABINET FABDB371058 Common 1 X
15 6510 4500 BUZZER TAPE HGFC0000501  Common 1 X
Parts prices will be informed separately by Parts Price List.
Notes: N – New parts R – A : Essential
Q – Quantity used per unit B : Stock recommended
R – Rank C : Others
X : No stock recommended
— 7 —

— 8 —
10
11
7
8
3
5
13
614
15
12
9
4
12
EXPLODED VIEW