Compaq CRT Monitor s7500 Service Guide - Page 14

HP S7500/MV7500/CV7500 below 4.0 V, the ABL function will happen. 3-3-8 H/V size breathing compensation 1. Beam current issensed as above section (3-3-7 item2) and this voltage routes throughR451, R468, C470 then through R437 to pin 31 of I401 for H. size compensation. 2. HV voltage is detected through T402(FBT) pin 11. C481, R4F4, R4F8, C430, R411, pin 5, 6, 7 of I403 (KA324) then through R302 to I401 pin 21 for V. size compensation. 3-3-9 Dynamic focus circuitry The dynamic focus is applied to improve the corner focus performance, it includes horizontal and vertical dynamicfocus. 1. Horizontal dynamic comes fromIdy current through T403, R434, C448, R428 andfeed to FBT dynamic focus pin (T401 pin 12). 2. Vertical dynamiccomes from pin 32of I401 through C315,R309, R326, R322, R323,Q301, R324, R325 and feed to FBT dynamic focus pin. 3-4 Power Supply Section 3-4-1 AC Rectifier The circuit can accept 90 V to 264 V AC input through D801~D803 bridge diodes and C808 filtering to get DC 126 V~364 V for power conversion in T802. 3-4-2 Line Filter It consists of C803,T801, C804, C805, C808, C819, C807, C817 and meets EMI regulation. 3-4-3 Power LED Status 1. The LED has 3 leads with common cathode to emit green and amber color light for different power saving states. It is controlled by CPU. 2. Normal : Green light Amber LED is off because CPU pin 29 is 1.96V and pin 24 is 0.45V, only green LED is turned on. 3. Off Mode : Amber light CPU pin 24 is 1.87V and pin 29 is 0.46V, then green is off and amber is illuminated. 3-4-4 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. 3-4-5 PWMControl 1. Start Up The I801 (5S0765C) gets power from R807, R808, C830 and pin 3 voltage reaches 15 V for starting up. The I801 starts oscillation at 20 kHz, pin 1 output to drive T802. Switching on, R819 set up an 15 V to keepI801 workingthrough D809auxiliary voltage. Page 12