A1502 820-3476-A intermittent backlight

[bridportpcrepair]

Hi guys

Got an A1502 here that has a backlight issue. No sign of any liquid damage on the board, all seems clean.

The screen has a display, but the backlight is intermittent. By that I mean that sometimes it will boot normally, screen will light, all is good.

Sometimes however it won't light up, it has a display but no backlight.

If I close the lid, the screen turns off as usual, opening it again results in no backlight most of the time.

Is there any point I should be starting to look at first?

PPV_OUT_S0_LCDBKLT (measured at Pin1 of LVDS connector) is 38v when functioning but reads at 11.5v when backlight is off.

I dimly recall something about SMC_LID and the hall sensor - is that a common area I should look at?

Many thanks

 

[bridportpcrepair]

Can't delete my post so I'll update - there IS liquid damage, didn't see the tiny spot of corrosion right underneath the backlight controller, will sort that and post back if there's still a problem!

Cheers!

 

[2informaticos]

If cleaning board doesn't help, be sure to use original charger.
MagSafe 1 to 2 adapter can cause that...

 

[bridportpcrepair]

Cleaning the board (removed the Q7700 IC and cleaned / resoldered), and the backlight driver, all seems well now with an instant backlight response rather than the delayed response I was getting before.

However, wasn't aware of the Magsafe 1->2 adapter issue - will lodge that in the memory bank!!

Many thanks