Sharp ER-A440 Service Manual page 22

7) Caution
CAUTION
If fuse F2 should be blown, the dot head solenoid may be shorted. Be
sure to check the head impedance and driver breakdown.
When fuse F2 is blown:
Remove F2, and perform the service resetting. The set the mode
switch to a position other than SRV and SRV' and turn off the
power.
Install fuse F2 (1A) and turn on the power.
If the fuse blows with the above operation, driver 4AC16 may be
shorted.
Turn off the power.
Disconnect the printer cable from the printer. Measure impedance
between the printer body connector pin 5 and the following pins:
1, 3, 9, 11, 13, 21, 25
The impdenace must be 10.5
If impedance is outside the above range, the dot solenoid is bad.
Replace the dot head unit.
+24V
DOT1~DOT7
8. Drawer drive circuit
VRESC
51 DR0
52 DR1
CPU
50
DOSP
R42
C97
47K
1000P
The drawer is directly supported by the CPU. No action starts when
the power supply is not steady as the output stage of the driver is
pulled VP by VRESC signal.
Drawer open and close is sensed with the microswitch provided in the
drawer whose signal is level converted with R74 and R73 and directly
read by the CPU.
10%.
5 VCOM
7 VCOM
17 VCOM
23 VCOM
1 DOT3
3 DOT7
9 DOT5
11 DOT2
13 DOT1
21 DOT4
25 DOT6
+24V
DRAW0
IC18
DRAW1
TD62308F
R143 4.7K
R144
1K
Fig. 8-1
9. Key, display, time buzzer controls
MPCA7
CPU
ST0~ST7
KR0~KR7
KR10,KR11
Key board
Display
VCC
1) Power on sequence
During service interruption, the CKDC8 senses POF within 500msec.
When service interruption is cancelled by turning on the power, the
CKDC8 cancels resetting of the CPU in the command mode. After
initializing each port, the CPU reads the start condition (1 byte).
POF
+24V
RES1
Drawer
solenoid
SHEN
LDRQ
After sampling POF High, the CKDC5 performs mode scan and key
scan at
the CPU initializes each port at
After being cancelled, the CPU reads the start condition without fail to
set the sift mode. If, however, the first starting is made in other than
SRV mode after the CKDC8 resets the CPU without request from the
CPU, the CKDC8 sets the start condition supposing that starting is
made in SRV mode.
4 – 15
HTS
HTS1
STH
STH1
SCK
SCK1
RESET
RESET
INT2
POFF
LDRQ
P11
ERC
P10
SHEN
P12
RES
P-OFF
RES0
RES0
Driver
G1~G10
a~g,DP
Driver
2
B
BUZZER
Fig. 9-1
1 2 Start condition
Fig. 9-2
, then cancels resetting of the CPU. After being cancelled,
and reads the start condition.
HTS
STH
SCK
RES1
LDRQ
ECR
SHEN
POFF
VDD
RESET
ST0~ST7
KR0~7,KR10,KR11
T0~T9
a~g,DP
CKDC 8
Next command