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4-3-7 Contrast Section
1. Contrast is controlled by I701 through I
2. Beam current is detected through T 101 (FBT) pin 7, D106, C109, Q102, R108, R121, R122 to control
I501 pin 22 voltage. When I501 pin 22 voltage drops below 5V, the ABL function will happen.
4-3-8 Dynamic focus circuitry
The dynamic focus is applied to improve the corner focus performance, it includes horizontal and vertical
dynamic focus.
1. Vertical dynamic comes from I401 pin 32 and is amplified through C105, Q101, C137, and feed to FBT
dynamic focus pins R133, R132, Q101.
2. This amplifier need 200V voltage supply, it comes from FBT pin 8 and rectified through L102, D101, and
C102.
4-4 Power Supply Section
4-4-1
AC Rectifier
The circuit can accept 90 V to 264 V AC input through D801 bridge diodes and C808 filtering to get DC 126
V~364 V for power conversion in T802.
4-4-2
Line Filter
It consists of C801, C802, C803, C816, C820, C823, T801, T804 and meets EMI regulation.
4-4-3
Power LED Status
1. The LED has 3 leads with comm on cathode to em it green and amber color light for different power
saving states.
2. Normal : Green light
3. Off Mode : Amber light
4-4-4 Auto Degaussing
When S801 turns on, pin 27 of I701 will send a signal to Q802 and turns on RL801 for degaussing. After 4
seconds, it will turn off RL801 automatically.
4-4-5 PWM Control
1. Start Up
The I801 (KC3843B) gets power from R846, Q821, R849, R 848, D826, D828, D822 and pin 7 voltage
reaches 8 V for starting up. The I801 starts oscillation at 22 kHz, sawtooth on pin 4 and pin 6 output to
drive Q803/T802. Once Q803 switching on, D806, C804 set up an 15 V to keep I801 working through
D821 auxiliary voltage.
2. Regulation
The DC O/P voltage is proportional to the auxiliary voltage, so I801 pin 2 senses the feedback voltage
from the divider R802, R823, VR801 and R820 to compare with the built-in 2.5 volts reference voltage for
error amplifier operation. Finally pin 6 can modulate the different duty cycle by VR801 setting to achieve
regulation purpose.
2
C bus to I501 (LM1267) directly.
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