49
5.6.4 Defective Sensor
All sensors transmit and receive infrared light. The front (F) and back (B) document sensors are slot
sensors that activate when the slot is blocked by a document. The back (B) and skew (S) sensors used
in automatic alignment printers are reflective sensors that activate when an inserted document reflects
light back on the sensor. The cover (C) and left home (L) sensors are toggled by metal flags that enters
the sensor slots.
Press 9 0 FUNCT to run diagnostics and display “SENSORS” and the letters LFBC (& S if auto
alignment is installed). Place an object in any sensor’s light path to remove the corresponding sensor
letter from the display. Press ENTER to return to READY status.
Symptom
Condition
Remedy
Rollers run continuously
before a document is inserted
and no F displayed during 90
FUNCT diagnostics.
Front document sensor light
path is blocked by paper, dust,
a bent input tray or guide.
Sensor may be bent .
Clear light path with
compressed air to the sensor.
Align input tray or input guide
to its proper position.
Rollers run continuously after
a document is ejected and no
B displayed during 90 FUNCT
diagnostics.
Back document sensor light
path is blocked by paper, dust,
a bent input tray or guide.
Sensor may be bent .
Clear light path with
compressed air to the sensor.
Align input tray or input guide
to its proper position.
Carriage drives into the left
side of the printer.
94 FUNCT parameters are
incorrect
Defective “home” sensor.
Check 94 FUNCT parameters
against label under the cabinet
lid next to the display.
Remove and replace the home
sensor.
Carriage drives into the right
side of the printer.
Home sensor is disconnected
from the main PCB.
Reconnect home sensor to the
main PCB
C
over Sensor
F
ront document
sensor
B
ack document
sensor
L
eft or Home sensor
DP6 all & DP7 without automatic alignment
DP7 with automatic alignment
F
ront document
sensor
B
ack document
sensor
S
kew sensor