Macbook A1278 M97 LCD backlight problem

[yakideo]

Hi,

I recently bought a used Macbook Late 2008 Aluminum, A1278 M97 MB467LL/A with a non functioning backlight.

Currently I traced the problem to the Q9806 mosfet, I get 12.6V at the source however the drain doesn't seem to want to open. I check the functionality of the mosfet with a multimeter and it's looks good.

Looking at the schematic I can see that the Q9807 mosfet is supposed to drive the Q9806's gate low however the Q9807 is missing from the motherboard. It looks like it never was fitted on the motherboard in the first place but I could be wrong and the previous owner might have removed it.

It's my understanding that if there is no voltage on the PPBUS_S0_LCDBKLT_PWR line then the WLED driver won't be enabled.

Is there anyone with some macbook backlight experience who can shed some light on my issues?

[polytek]

Re: Macbook A1278 M97 LCD backlight problem

check the fuse:F9700
then enable sugnal:PPBUS_SW_LCDBKLT_PWR of U9701 if ok reflow oe change U9701

[yakideo]

Re: Macbook A1278 M97 LCD backlight problem

I think I blew the 1-wire over voltage protection so I will have to repair that first. Still waiting on better tools I bought.

The fuse wasn't for the backlight wasn't blown. How do you mean when you say I should enable PPBUS_SW_LCDBKLT_PWR? Do you mean I should pull that pin high?

[polytek]

Re: Macbook A1278 M97 LCD backlight problem

I think I blew the 1-wire over voltage protection so I will have to repair that first. Still waiting on better tools I bought.

The fuse wasn't for the backlight wasn't blown. How do you mean when you say I should enable PPBUS_SW_LCDBKLT_PWR? Do you mean I should pull that pin high?

no, i'm sorry but i mean that you have to check the signal named: PPBUS_SW_LCDBKLT_PWR