MacBook Pro A1286 Mid 2012 no power, no LED on the charger

[Gigabit2]

Got a MacBook Pro A1286 15 here, mid 2012. Doesn't power on and no LED on the charger.

Looks like some possible liquid damage on the keyboard but board looks okay from a visual inspection.

Can somebody please kindly help me in diagnosing this one?

[mon2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

1) Post the 820-xxxx from the logic board.

2) Are you using a known good and original power adapter for this unit ?

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Hi mon2 once again

1. 820-3330-B
2. Yes - and verified working with another laptop

[mon2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Hi.

See attached. Post the voltage readings for these points with the external power adapter attached.

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Hi mon2,

Great news, I replaced the MagSafe DC in board and system now turning on with bong!

Sadly, no backlight on the display - have shined light from phone and can see screen, so looks like backlight issue once again?

Can you help?

[mon2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Check fuse @ F8400 - measure the voltage on each side.

Measure and post the readings of:

EDP_BKLT_EN

BKLT_EN_R

BKLT_SCL

BKLT_SDA

PPVOUT_S0_LCDBKLT

If PPVOUT_S0_LCDBKLT is low and not 25++ volts then remove all power.

Meter in resistance mode. Check the resistance to ground of PPVOUT_S0_LCDBKLT (L8420, pin # 2).

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Hi mon2,

I cannot see a F8400 fuse on my boardview here.

I cannot see any references to the components you reference, can you provide some guidance?

I am using schematic and boardview from: https://www.badcaps.net/forum/showpo...40&postcount=6

[mon2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Revised list:

Check fuse @ F9700- measure the voltage on each side.

Measure and post the readings of:

BKL_EN

BKL_SCL

BKL_SDA

PPVOUT_SW_LCDBKLT


If PPVOUT_S0_LCDBKLT is low and not 25++ volts then remove all power.

Meter in resistance mode. Check the resistance to ground of PPVOUT_S0_LCDBKLT (D9701).

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

F9700 showing 12.5V on one side, 0V on other.

Have checked continuity on fuse and no continuity, other side of the fuse is showing as 0.05V to ground so I think this fuse is blown?

BKL_EN: 0V on all modes
BKL_SCL: 3.3V
BKL_SDA: 3.3V
PPVOUT_SW_LCDBKLT: .015 on 2V mode

[mon2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Agree - the fuse looks to be blown and should be replaced. Then test again.

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

New fuse ordered, is there any temporary check I can do safely before it arrives to verify? Can I bridge the connection?

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

mon2, D9701 PPVOUT_S0_LCDBKLT showing 00.3 to ground on 200m mode.

[mon2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

The fuse is there to prevent an excessive current spike. While tempting, I would wait for the fuse (order some spares) to arrive.

The D9701 resistance to ground is not good. Can you use a higher scale on the meter and measure again ? If indeed you are seeing a low resistance like 0 ohms then you have a short.

Consider to desolder D9701 and then measure the resistance to ground again of PPVOUT_S0_LCDBKLT. What is the resistance ?

The idea is to isolate the 2 legs of the circuit (left / right side) to determine where is the short. The short may be in one of the caps to the right side of D9701.

If after removing D9701, you still have a low resistance to ground then remove both caps @ C9797 & C9799 and measure again. If required, remove C9796. Measure again.

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Thanks mon2, fuses ordered as advised. I will fit with hot air when they arrive, old fuse already removed.

I will try the D9701 steps when new fuse fitted.

I wonder if the display caused a short, is there any way I can test the screen without causing it to short again?

[mon2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

You can try to fix the short without the fuse.

Remove the display and check the resistance to ground of the backlight rail. It should not be as low as you have posted.

This must be repaired first else the fuse will blow again.

Remove the lcd, check the resistance.

Then remove the diode and check again.

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Hi mon2,

I replaced the backlight fuse F9700 and showing good continuity. Laptop turning on and backlight now working! Booted successfully as well.

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Should I still do the D9701 steps?

[mon2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

No - I think you are good to go ?

The other tests were only if the backlight still failed to turn on.

Well done !

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Oh no! @mon2

It booted into recovery for reinstall then screen suddenly went black.

Now, powers on with green light on charger but no bong and screen is black. Indicator light on the front of the machine is solid white. Fans spinning

What next?

[Gigabit2]

Re: MacBook Pro A1286 Mid 2012 no power, no LED on the charger

Continuity on backlight fuse still looking good so hasn't shorted.