Hi,
I'm stuggling with this board.
I got the board from a laptop which had obviously been taken apart previously.
At first, I only got 5V on the charger, so I replaced one of the CD3215s (the one that got hot) and then I got 20V and the board was booting fine.
Except there was no backlight.
Checking the backlight regulator area, I found 2 resistors (R8445 and R8442) that had been ripped off the board. Probably by the previous guy who wasn't careful enough when manipulating the board. One of them is responsible for feeding PP5V_S0 to the chip, and the other one gives the BKLT_EN signal to the chip, so I thought it would be logical to have no backlight and it should be an easy fix.
But after putting back those two resistors, still no backlight.
The fuse is not blown, as usual.
I have 13 volts at the input of the PMOS (Q8400) but nothing out of it.
Its gate measures about 12 volts, which explains why it's not turning on.
There is no short to PPBUS on the gate. Both resistors of the voltage divider are measuring good.
I can see the BKLT_EN_R signal to the chip going from 0V to 3.3V a few seconds after I plug the charger in.
But the chip never ties BKLT_SD to ground, therefore not activating the voltage divider.
I do have keyboard backlight.
LID_OPEN is high.
I have tried to replace U8400, but still the same issue.
I'm stuggling with this board.
I got the board from a laptop which had obviously been taken apart previously.
At first, I only got 5V on the charger, so I replaced one of the CD3215s (the one that got hot) and then I got 20V and the board was booting fine.
Except there was no backlight.
Checking the backlight regulator area, I found 2 resistors (R8445 and R8442) that had been ripped off the board. Probably by the previous guy who wasn't careful enough when manipulating the board. One of them is responsible for feeding PP5V_S0 to the chip, and the other one gives the BKLT_EN signal to the chip, so I thought it would be logical to have no backlight and it should be an easy fix.
But after putting back those two resistors, still no backlight.
The fuse is not blown, as usual.
I have 13 volts at the input of the PMOS (Q8400) but nothing out of it.
Its gate measures about 12 volts, which explains why it's not turning on.
There is no short to PPBUS on the gate. Both resistors of the voltage divider are measuring good.
I can see the BKLT_EN_R signal to the chip going from 0V to 3.3V a few seconds after I plug the charger in.
But the chip never ties BKLT_SD to ground, therefore not activating the voltage divider.
I do have keyboard backlight.
LID_OPEN is high.
I have tried to replace U8400, but still the same issue.