JVC 340 SC - Manual (Page 19)

Chapter 2—Functional Descriptions
Model 330, 340SC and 370SC Service Manual 2–7
The Arc Lamp power supply is a current-controlled supply with an open circuit
voltage of about 170V. When the Arc Lamp is operating at steady state, the power
supply provides the current set by the technician. The output of the supply has a
large capacitor that will, on initial ignition of the Arc Lamp, provide the very high
initial current necessary to ionize the xenon gas in the lamp and sustain the arc.
The current setpoint is initially set at the factory and must be reset by the
technician whenever an Arc Lamp is replaced.
AC INPUT
220-240vac
50Hz
STANDBY/
I/O CONTROL
+5v, +24v
J502
J500
J503 (-)
J504 (+)
To
Backplane
To
Arc Lamp
Via
Ignitor
POWER
FACTOR
CORRECTION
LOW VOLTAGE
Power Supply
+5v,+6.3v,+-15v,
+24v,+48v,+107v
ARC LAMP
Power Supply
and Boost
+22v/68a
∇
+170v/1.0a
/LVPSNBL
/ALENBL
From
System
Controller
/FANENBL
J502
∇
Model 330. Model 340SC = +25V/80a; Model 370SC = +30V/100a.
Figure 2-3 System Power Supply Block Diagram.
Normal system power-up (Electronics and Lamp):
1. Upon receipt of Power-On command, SCB pulls /FANENBL and
/ALENBL lines low.
2. +24V Standby and Arc Lamp power supplies turn on.
3. When Arc Lamp lights (run voltage sensed by a window comparator in the
SPS), SPS pulls /LAMPLIT line low.
4. When SCB senses /LAMPLIT low, SCB pulls /LVPSNBL line low.
5. Low voltage supplies turn on.
6. SCB senses +5V supply at correct level and enters normal program
sequence.
Lamp only power-up:
1. Upon receipt of Lamp-On command, SCB pulls /FANENBL and
/ALENBL lines low.