AR-FN1 (serv.man10). ARFN1 Service Manual-Description of Circuits - Sharp Copying Equipment Service Manual (repair manual). Page 9

This circuit checks whether the finisher is connected to the copier,
both the top and front doors are opened. It is connected to mi-
croswitches whose contacts are closed when the finisher is con-
nected to the copier or the doors are closed. 

Each switch is connected in series from 

+

24V so that it becomes a

power supply switch for the drive. That is, 

+

24V is not conducted to

the drive if all the 3 microswitches are closed. 

When the finisher is connected to the copier, the microswitch turns
on, letting 

+

24V be applied to ZD4. This allows electric current to flow

to the base resistance of the transistor array TD62504 (IC19), thus
turning on the transistor to change the expansion I/O PG1 (DSW1
signal) to L level.

When the finisher is disconnected from the copier, the transistor is
turned off to change the expansion I/O PG1 to H level. ZD4 (RD6.2E)
has a threshold level preset, to increase detection speed when the
supply of 

+

24V is cut off. The levels of PG2 and 3 (DSW2, 3 signals)

also change when the top and front door switch is opened and
closed.

In addition, when 

+

24V power supply from the copier is cut off, the

expansion I/O PG0 (PWD signal) level changes at the above circuit.

Here are logic’s at the time of the power supply from the copier being
cut off and the doors opening and closing being detected.

←

Upper Lower

→

Status

Expansion

I/O port

PG0

PG1

PG2

PG3

Remarks

Signal

name

PWD

DSW1 DSW2 DSW3

Power supply from
copier is cut off

H

d.c

d.c

d.c

Disconnected from
copier

L

H

d.c

d.c

H:

Power supply cut off (door open)

L:

Conducting (door closed)

d.c: Unknown (no status is shown because power is cut off at up-

stream)

PWD    54
DSW1  55
DSW2  56
DSW3  57

BR10

10Kx5

O1
O2
O3
O4
O5
O6
O7

COM

I1
I2
I3
I4
I5
I6
I7
GND

TD62504F

IC19

16
15
14
13
12
11
10

9

PWD
DSW1
DSW2
DSW3

5
6
7
8

+5V

(IC03)

PG0
PG1
PG2
PG3

RD6.2EB2

ZD05

RD6.2EB2

ZD04

RD6.2EB2

ZD03

RD6.2EB2

ZD06

+24VIN

+24V1

+24V1

+24V2

+24V2

+24V

+24V

I/O

2 3 4 5 6

4

3

2

1

Power supply +24V

Upper

Lower

Copier connection sw

Upper door sw

to each motor and
solenoid clutch

Finisher door monitoring circuit

Front door sw

Microswitch x 3

Normal: SW ON
Copier separated
or door open: SW OFF

9 – 7