ER-A880 (serv.man5). ERA8DP One Line Display Service Manual - Sharp EPOS Service Manual (repair manual). Page 2

The ER-A8DP is a customer display option for the ECR.

•

7-segment display:
Font:

Positions:

7 positions

Character size:

13.0(H) 

✕

 6.0(W) mm

1) When the pin-14 output level of the comparator IC1C is at high

(open), the positive voltage of the pin-9 becomes about +2.7V by
the voltage division with the positive side divider resistors (parallel
connection R112, R111, R10) and R109. At this point, the nega-
tive voltage on the pin-8 is charged from R104 to C101 and begins
to rise.

2) When the negative side voltage turned higher than the positive

side, the output is then inverted to low level.

3) When the pin-14 output of the comparator IC1C has turned low,

the pin-9 positive voltage turns to about 2.3V by the voltage divi-
sion with R111 turned to the negative side voltage dividing resistor
and the parallel inserted resistors R109 and R111, and R10 volt-
age division. Then, for the negative voltage on the pin-8, the
charge in C101 is discharged through R104.

4) The output turns high when the negative side voltage went lower

than the positive side voltage.
Above steps 1) through 4) are repeated to oscillator.

1) The converter transformer is driven with the signal from the oscilla-

tion circuit in 2-2-1. In case the feedback signal and the overcur-
rent are not detected, it will be driven by this circuit.

These signals are used for input to the comparator IC1D, pin-11 (+)
line of the feedback circuit.

 

1

  –29V feedback signal

 

2

 Overcurrent monitor signal (reter to "2-1-4")

1) The feedback from –29V line is sent to the pin-11 of IC1D as a

voltage divided by R113 and R101. The comparator IC1D com-
pares the signal from the pin-11 with the comparator IC1C pin-8
signal of the oscillation circuit to control the feedback.

2) When the level on the pin-10 goes above that of the pin-11 at a

rising of the comparator IC1D pin-10 signal (Q1 turns on when the
comparator IC1A of the basic drive circuit turned off), the compa-
rator IC1D output turns on and Q1 turned off to stop driving the
converter transformer.
If the level of the pin-11 signal was  higher than the level of the
pin-10 (–29V being shallow), the drive time prolong. If the level of
the pin-11 signal was lower than the level of the pin-10 (–29V
being deep), the drive time shortens.

R111

51k

9

8

14

IC1C

IR2339N

R109

10KF

R104

100K

C10 1
330P

R112

1.5K

R10

10KF

VCC
(+5V)

VCC
(+5V)

5V

0V

2.7V

2.3V

14Pin

9Pin

8Pin

2.7V

2.3V

IC1A

IR2339N

6

Q1

C3144

7

3

12

1

5V

From oscillation circuit

A

C103

0.1µ

IC1D

IR2339N

10

11

13

R113

30KF

From pin-8 of IC1C

-29V

VCC(+5V)

A

R101

2.4K

B

2.7V

2.3V

2.5V

High

Low

High

Low

ON

OFF

10pin (-)

11pin (+)

TR1 output

Comparator IC1D

Comparator IC1B

Comparator IC1D

pin-2 output

pin-13 output

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