Sykulski
Member
This one came in with severe water damage. After ultrasonic cleaning and fixing CPU VCORE power issue it started up with no backlight. I knew it would because it had a lot of corrosion around backlight circuitry. I changed all corroded resistors and caps around LP8550 and also the LP8850 itself. Some traces needed wire. Also the pulldown resistor on BKLT_PWM was corroded so I have changed it and put a wire on the broken trace.
Now the backlight is working partially. When I start the computer backlight turns on. The brightness is 100% even if I turn it down. BKLT_PWM is pulsing - long pulses on high brightness and short pulses on low brightness - but still full brightness around 40V on LCD connector. But when computer goes to sleep backlight does not come back on every time. Sometimes it comes right away - sometimes after 30 seconds - and sometimes not at all before I shut down and turn the machine back on. When backlight is not working after sleep then I get 19-20V on LCD connector.
I tried giving BKLT_PVM 3V from PP3V3_S0 but still only 19V on backlight after sleep.
What am I missing ?
Now the backlight is working partially. When I start the computer backlight turns on. The brightness is 100% even if I turn it down. BKLT_PWM is pulsing - long pulses on high brightness and short pulses on low brightness - but still full brightness around 40V on LCD connector. But when computer goes to sleep backlight does not come back on every time. Sometimes it comes right away - sometimes after 30 seconds - and sometimes not at all before I shut down and turn the machine back on. When backlight is not working after sleep then I get 19-20V on LCD connector.
I tried giving BKLT_PVM 3V from PP3V3_S0 but still only 19V on backlight after sleep.
What am I missing ?
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