Compaq HP wf1907 free download

File name wf1907.pdf

HP HP_LCD_W1907&WF1907_SM061031V00 Service HP WF1907 & W1907 June.19th-2006 Service Manual 01. 02. 03. 04. 05. Table of Contents Power Board Operation Theory----------------------------------------------------------------01 Inverter Circuit--------------------------------------------------------------------------------------02 Interface Operation--------------------------------------------------------------------------------03 Troubleshooting------------------------------------------------------------------------------------10 Schematic-------------------------------------------------------------------------------------------24 Safety Notice Any person attempting to service this chassis must familarize with the chassis and be aware of the necessary safety precautions to be used when serving electronic equipment containing high voltage. Published by LITE-ON Service Printed in Taiwan © All rights reserved Subject to modification 31th Oct-2006 HP W1907& WF1907 Service Manual 1. Power Board Operation Theory 1.1 Line filter consists of C801, T801, C802, C803, C804, C808, C809, C815, C819, C820, C825. It eliminates high frequency interference to meet EMI's requirement. 1.2 Rec & Filter Bridge diode D812, D813, D814, D815 converts AC source into pulsed DC. This pulsed DC is smoothed and filtered by C805. R802 is an NTC (negative thermal coefficient ) resistor, used to reduce inrush current to be within safe range. 1.3 Power transformer : T802 converts energy for square wave from power source C805 to secondary side to generate +5V, +12V and +22V. 1.4 Output : The square wave from T802 is rectified by D808 D809, D810, then filtered by C817, C818, C824, C823, C830, C833, C822 to generate +22.5V and +12V, +5V respectively. 1.5 Driver : Q803 drive T802 from PWM control of I801 for power converted. 1.6 FB : Negative feedback CKT consists of photo coupler I802 and adjustable regulator I803. It can maintain output voltages +22.5V and +12V, +5V at a stable level. 1.7 PWM : 1.7.1 1.7.2 Start : When power is turned on. C807 is charged a 11V and a starting current above 40uA to pin 1 of I801. I801 starts to oscillate and outputs a pulse train through pin 6 to drive Q803. OPP : When Q803 turns on, C805 supplies a linearly increasing triangle current through the primary inductance of T802 to the driver Q803, once the peak value of this current multiplied by R811 exceeds 0.52V, pulse train will be turn off immediately to protect Q803, T802 from being burned out. Regulation : If output voltage +22V goes up, the R terminal of I803 gets more bias, accordingly photo transistor and photo diode flows more current. The voltage of pin 2 goes up too, making the pulse width of pin 6 to become narrower. So the output voltage +22V will be pulled down to a stable value. 1.7.3 1.7.4 OVP : If +22.5V goes up too much, the induced voltage on pin 4 of T802 becomes large also. Suppose that it is over 20V. The pulse train at pin 6 goes down to zero, shutting Q803 off immedi