Euro-500TX Handy
© Elcom, s. r. o.
Service manual
30
Euro-500TX Handy
© Elcom, s. r. o.
Service manual
31
3.4 Printing head position sensor
This sensor detects whether the printing head is up or down. Activation of the head in its top position could
destroy the head or drastically decrease the head durability. The circuit and software were designed so that
the printing head cannot be possibly activated in its top position.
Type
photoconductive detector
Head up
log. “0”
Head down
log. “1”
Specification
diode: I
F
= 50 mA maximum
U
R
= 6 V maximum
transistor: U
CEO
= 35 V maximum
I
C
= 20 mA maximum
3.5 Paper tape presence detectors
The printer has an internal paper tape presence sensor for the journal tape (output signal PS2x). Head
activation without paper in the printer can destroy the head or drastically decrease its durability. There is an
external paper tape presence sensor for the receipt tape (used photoconductive detector TCST 1103).
3.6 Overall time diagram
HS
R53
47k
VCC1
X
R7
470R
M
ain
P
C
B
In
te
rco
n P
C
B
Fig. 3.6 Outer part of the head position
sensor
R31
68k
VCC1
PS2
R74
68k
VCC1
PS1
VCC1
X
R10
470R
R8
220R
Fig. 3.7 Sensor circuit on the main PCB
Fig. 3.8 External sensor circuit on the Inter-
connect PCB
576 bits
50
dots
576 bits
576 bits
576 bits
F
A
F
B
F
B
F
A
DATA IN
CLOCK
LATCH
STB1
STB2
STB3
STB4
100
dots
10
dots
10
dots
10
dots
10
dots
100
dots
30
dots
100
dots
30
dots
100
dots
60
dots
Fig. 3.9 Overall time diagram
