Service manual

CIRCUIT THEORY
+5 V
P1 PJ
R12
NO-PAPER SENSOR SWITCH
15 K
PA2~1_0--------------~----~1818~----o
U5D
(6532)
1616~----------~
+5 V
R54 P3 J3
PF KEY
470 n
PA3~1_1 ____________ 4- ____ ~1 1
U2D
PA5 ~1_3 ____ a
>---~----~ 3 3 ~--;)I------+
2
U5D
(6532)
1
PAPER ADVANCE SWITCH AND INDICATOR CIRCUIT
Paper Control Logic
A normally closed
micro switch located behind the platen opens when paper is loaded in the printer.
When no paper is in
the printer, the switch is closed causing a "Iow" potential to be input at U5D
pin 10 (PA2).
Depressing
the push button on the front of the printer causes a form feed to occur. Form feed length
is
software controlled. A "Iow" potential is applied to U5D pin 11 (PA3) when the push button is
depressed.
An LED inside the push button case indicates the printer is powered on. A flashing LED
indicates paper out. The output U5D pin 13 goes II low" , U2D pin 2 goes "high", and the LED turns on.
15