Good afternoon. This laptop has its own history. It was brought to me a while ago to change the keyboard. Replaced the keyboard, after about two months the customer contacts me because it doesn't turn on anymore. I removed the cmos battery and put it back, the laptop starts working. For safety, I clean the Me Engine of the bios and resoldered the spi of the bios. After a week same problem. Even if I remove the backup battery, the laptop doesn't always work, often it doesn't turn on, no LEDs. I checked under the microscope but there are no traces of oxidation. I did some measurements on the ic charger and on the 3v and 5v pwm when the problem is present.
Only ac adapter, no battery
PU8901:
pin 1 19,5V
pin 2 19,5V
pin 3 18,9 V
pin 4 24,8 V
pin 5 3,06 V
pin 6 2,65 V
pin 7 0 V
pin 8 0v
pin 9 0v
pin 10 0v
pin 11 0v
pin 12 0v
pin 13 0v
pin 14 0v
pin 15 0v
pin 16 0v
pin 17 0,22v
pin 18 0,25v
pin 19 0,23v
pin 20 0,23v
pin 21 1,16v
pin 22 0v
pin 23 0v
pin 24 6v
pin 25 5,8v
pin 26 0,23v
pin 27 0,23v
pin 28 19.2V
PU8701
pin 1 0v
pin 2 0v
pin 3 3,30v
pin 4 0v
pin 5 0v
pin 6 0v
pin 7 0v
pin 8 0v
pin 9 2,28v
pin 10 0v
pin 11 0,42v
pin 12 19,47v
pin 13 0v
pin 14 0v
pin 15 0v
pin 16 0v
pin 17 2,28v
pin 18 0v
pin 19 0v
pin 20 0v
*******
I found the problem, there was oxide under pu8803. The oxide was barely visible
Only ac adapter, no battery
PU8901:
pin 1 19,5V
pin 2 19,5V
pin 3 18,9 V
pin 4 24,8 V
pin 5 3,06 V
pin 6 2,65 V
pin 7 0 V
pin 8 0v
pin 9 0v
pin 10 0v
pin 11 0v
pin 12 0v
pin 13 0v
pin 14 0v
pin 15 0v
pin 16 0v
pin 17 0,22v
pin 18 0,25v
pin 19 0,23v
pin 20 0,23v
pin 21 1,16v
pin 22 0v
pin 23 0v
pin 24 6v
pin 25 5,8v
pin 26 0,23v
pin 27 0,23v
pin 28 19.2V
PU8701
pin 1 0v
pin 2 0v
pin 3 3,30v
pin 4 0v
pin 5 0v
pin 6 0v
pin 7 0v
pin 8 0v
pin 9 2,28v
pin 10 0v
pin 11 0,42v
pin 12 19,47v
pin 13 0v
pin 14 0v
pin 15 0v
pin 16 0v
pin 17 2,28v
pin 18 0v
pin 19 0v
pin 20 0v
*******
I found the problem, there was oxide under pu8803. The oxide was barely visible
