UP-3300 (serv.man13). Service Manual - Sharp EPOS Service Manual (repair manual). Page 3

The UP-P16DP is a remote display option for the POS.

•

7-segment display:

Font:

Positions:

11 positions

Character size:

12.0(H) 

×

 6.0(W) mm

•

Dot display:

Pattern:

Positions:

16 positions

1) When the pin-14 output level of the comparator IC4 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 R52, R42, R49) and R50. At this point, the negative
voltage on the pin-8 is charged from R51 to C29 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 IC4 has turned low, the

pin-9 positive voltage turns to about 2.3V by the voltage division
with R42 turned to the negative side voltage dividing resistor and
the parallel inserted resistors R50 and R42, and R49 voltage divi-
sion. Then, for the negative voltage on the pin-8, the charge in
C29 is discharged through R51.

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 oscil-

lation circuit in 2-1-1. 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 IC4, pin-11 (+) line
of the feedback circuit.

 

  –26V feedback signal

 

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

1) The feedback from –26V line is sent to the pin-11 of IC4 as a

voltage divided by R46, R43 and R55. The comparator IC4 com-
pares the signal from the pin-11 with the comparator IC4 pin-10
signal of the oscillation circuit to control the feedback.

2) When the level on the pin-10 goes above that of the pin-4 at a

rising of the comparator IC4 pin-10 signal (Q1 turns on when the
comparator IC4 of the basic drive circuit turned off), the compara-
tor IC4 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 (–26V being shallow), the drive time prolong. If the level of
the pin-11 signal was lower than the level of the pin-10 (–26V
being deep), the drive time shortens.

5.60

1.19

0.85

1.33

0.99

9.00

( Unit in mm)

R42

51k

9
8

13

IC4C
BA10339

R50 10KF

R51

100K

C29
330P

R52
1.5K

R49

10KF

VCC
(+5V)

VCC
(+5V)

5V

0V

2.7V

2.3V

14Pin

9Pin

8Pin

2.7V

2.3V

IC4B
BA10339

4

Q1
C3144

5

3

12

2

5V

From oscillation circuit

A

C35

0.1µ

5V

R45
1K

R43
13KF

R46
10KF

VCC

VCC

 11

 10

13

3

12

IC4D
BA10339

R55
2KF

C36
O.O15uF

-26.25V

A

B

From pin-8

of IC4C

2.7V

2.3V

2.5V

High

Low

High

Low

ON

OFF

10pin (-)

11pin (+)

TR1 output

Comparator IC4

Comparator IC4

Comparator IC4

pin-14 output

pin-13 output

– 1 –