Ld Safety Switches - Gestetner A294 Service Manual

2.4.5 LD SAFETY SWITCHES

CN403-2
+5V
CN401-27
+12V
CN403-1
CN403-3
–12V
To ensure technician and user safety and to prevent the laser beam from
inadvertently switching on during servicing, there are four safety switches inside
the front cover.
When one of the front covers is open, the 5 V line connecting to the LD drivers
(LDD) is disconnected. The above diagram shows one LD and driver circuit as an
example. There are four of these on the LDB board. Additionally, the OUT terminal
of the PWM IC is automatically set at a low level to prevent any power from being
supplied from the PWM IC to the LDD.
Even if 12 V is supplied from the op amp which controls the LD power level, the
power will be less than the minimum power required for LD lighting (5 mA) due to
the 2.7 kΩ resistor.
SM
CÓPIA NÃO CONTROLADA
PWM IC
21
OUT
12
PWR_REDUCE
+12V
+
–
–12V
LDB
2-37
CÓPIA NÃO CONTROLADA
CN404-1
CN404-3
LDD
2
WR_PULSE
2.7k
WR_LEVEL
3
LDA
LASER EXPOSURE
Left and Right
Front Door
Safety Switches
A294D998.WMF
A294/A295