ER-A570 (serv.man5). ERA570 Option Programming Manual - Sharp ECR Service Manual (repair manual). Page 70

The ER-A550 supplies +5V to +24V, and 

±

12V is generated from

+24V in the DC/DC convertor circuit.

Fig. 4-1

(1)

The PX signal from the OPC1 alternately turns on and off the
comparator output of IC 8 (pin 7), which causes Q1 to turn on
and off. (Circuit 

Α

 )

Fig. 4-2

T1: Software starting:

26.04us

Normal operation:

13.02us

∗

 After POFF cancel (Power ON), software start is made for

     13.3ms.

Duty (Q1: ON/OFF) : Software strating: 12.5%

Noemalperation : 25%

(2)

The potential at point 

α

  is 4.8V when the output voltage is

+12V(About +11V). A load fluctuation causes the +12V output to
change. At point 

β

  of the comparators (+) side, a triangular

waveform appears as shown in Fig. 4-2.

(3)

The comparator (IC No. 8...Circuit 

Β

), the potential at point 

α

 

is compared with that of point 

β

  . If the potential at point 

α

 is

lower than point 

β

  , Q1 activating time is prolonged to raise

the output voltage (by increasing the duty cycle). On the con-
trary, if the potential at point 

α

  is higher, the transistor activat-

ing time is hortened to decrease the output voltage (by decreas-
ing the duty cycle). As Q1 duties cycles are varied by detecting
the +12V output fluctuation in the comparator (Circuit 

Β

), the

output voltage is regulated at a constant level.

Fig. 4-3

Potential at point a changes according to a fluctuation in the
+12V output. Waveform at point a differs depending on the state
of +12V output.

(4)

The pin 3 output of the IC9 chip at circuit 

Χ

 is at a high level

when the pin 1 input is at 5V. But, when it drops below 4.5V, the
line goes to the GND level. This causes Q1 to turn off so that
+12V and 12V are shut off. It is provided for prevention from
malfunction in the logic circuit when the +5V supply from mal-
function in the logic circuit when the +5V supply from the ER-
A550 main frame drops.

∗

IC9: Not used

The ER-A5RS ports can be set to channel 1 - 7 and invalid (inhibit)
with SW1 on the PWB.

SW1 setting contents
SW1 1~3 are used for channel setting of RS-232 connector 1
(RSCN1).
SW1 4~6 are used for channel setting of RS-232 connector 2
(RSCN2).

+2 4V

+2 4V

+5 V

+1 2V

-1 2V

T800mA

+

C49

100µ

50V

R2 2

4.3K

IC9

1

2

D 2

+

+

C51

C52

RD 33E B1

ZD2

R1 7

2.7KG

8

4

2

3

+

-

R14

10KG

C28

330P

R1 3

10 0K G

+

-

6

5

R1 6

R1 5

10 K

10K

C

B

A

Q1

ZD1

RD27EB4

T1

H6752RC

+5 V

3

D 3

100µ35V x 2

R24

2.2K

1

R18

2.2KG

IC8

9393

7

IC8

9393

D1

E352

C50

10µ

16V

ZD3

RD5.1EL1

PX

c

a

b

+5V

GND

OFF

ON

+5V

GND

OFF

ON

OFF

PX

Q1
ON,OFF

c

Point

3.255µs

T1

ON

OFF

ON

ON

OFF

OFF

OFF

+5V

GND

500mV

+4.8V

+1.4V

GND

GND

+1.4V

+4.8V

+5V

PX

Q1
ON,  OFF

Point

a

b

c

Point

Point

a

Point

c

Point

+3V

*1

*2

*3

(a)

(0)

(1)

SW1

RSCN1

RSCN2

OPTCN1

SW1

RSCN1

setting

3

2

1

0

0

0

RS-232 invalid

0

0

1

Channel 1

0

1

0

Channel 2

0

1

1

Channel 3

1

0

0

Channel 4

1

0

1

Channel 5

1

1

0

Channel 6

1

1

1

Channel 7

SW1

RSCN2

setting

6

5

4

0

0

0

RS-232 invalid

0

0

1

Channel 1

0

1

0

Channel 2

0

1

1

Channel 3

1

0

0

Channel 4

1

0

1

Channel 5

1

1

0

Channel 6

1

1

1

Channel 7

Note
1) If RSCN1 port and RSCN2 port of the ER-A5RS are set to the

same channel, RSCN2 port becomes invalid and only RSCN1 is
valid.

2) If RSCN of the ER-A5IN and the ER-A5RS connector are set to

the same channel, the buses compete and the operation cannot
be assured. In addition, it may break the hardware. Never set the
two to the same channel. Be sure to set them to different channels
or to set invalid.

6

5

4

3

2

1

O

F

F

1

0

6

5

4

CN2

3

2

1

CN1

4  27