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

[Gigabit2]

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

Okay pins 1 and 2 on backlight fuse showing .002 to ground with 2V mode - but is same on both sides so fuse isn't blown again.

@mon2 looks like screen isn't even coming on now, also no bong and like I said LED light on the front not going off.

There is fan spin.

[mon2]

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

Oh no - we jinxed it.

What is the backlight voltage when ON ? Can you see any video with a flashlight ?

Watch this video to see if it helps:

https://www.youtube.com/watch?v=Ho2W902s5P8

[Gigabit2]

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

Hi mon2,

D9701 pin 2 PPVOUT_S0_LCDBKLT showing 0.00 on 20V mode, 0.02 on 200M mode. With power off.

Can see no video with flash light now

[Gigabit2]

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

F9700 showing 12.5V on both sides.

[Gigabit2]

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

Plot thickens!

Removed display and now powering on with video working to external monitor which means GPU okay.

Plugged display back in again and no video on screen built in or external. So perhaps a bad display or display cable?

How can I check?

[mon2]

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

Remove all power, remove the LCD display. Meter in the lowest resistance scale.

Check the resistance to ground of PPVOUT_S0_LCDBKLT (without the display).

What is the reading ?

[Gigabit2]

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

Tried another display and same issue, so looks like an issue inside the laptop then. Something is shorted when the display is connected? Perhaps the circuit in question only activates with display connected?

[Gigabit2]

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

C9000 PPVOUT_S0_LCDBKLT showing 00.4 on 200m mode @mon2

[mon2]

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

Can you confirm the meter scale with a pic ? Is that 200 Mega ohm scale ?

If yes, use the lowest scale to measure the same test point. Checking to see if you have a bad cap that is causing the boost regulator to fold back and turn off the backlight.

However, you have said there is no video on the LCD ?

Without the LCD, do you hear any (normal) boot chime ? Do you see the caps LED on the keyboard toggle after a while ?

[Gigabit2]

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

No video on two LCDs I’ve tried mon2.

Yes without LCD, hear boot chime and indeed video is output to external monitor via HDMI.

[mon2]

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

Are the LCDs known good and compatible for this logic board ?

[Gigabit2]

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

Are the LCDs known good and compatible for this logic board ?

Yes.

Indeed one LCD was showing image earlier today then suddenly went black during usage and has not come back since then.

[mon2]

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

The one that went black during use - was it mated with this logic board ?

Then it was killed ? Can you use this non-working LCD on a different logic board and see the video (with a flashlight) ?

[Gigabit2]

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

Not sure what mated means here but it was connected to this motherboard.

Do not have another logic board to try

[Gigabit2]

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

Mon2, surely must be logic board if two different displays showing no video at all?

[Gigabit2]

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

mon2, what voltages can I check for helping to resolve this issue?

[Gigabit2]

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

Can you confirm the meter scale with a pic ? Is that 200 Mega ohm scale ?

If yes, use the lowest scale to measure the same test point. Checking to see if you have a bad cap that is causing the boost regulator to fold back and turn off the backlight.

However, you have said there is no video on the LCD ?

Without the LCD, do you hear any (normal) boot chime ? Do you see the caps LED on the keyboard toggle after a while ?

Here is pic:



Yes, no video on the LCD.

Yes, without the LCD here normal boot chime - and when plugged in the laptop to external HDMI can see video output on external display.

[Gigabit2]

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

Caps lock coming on without display connected but with display connected, does not come on.

[mon2]

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

Hi. Just waking up from my beauty sleep.

Have you ever seen the lcd show you the apple logo or similar? I think you had graphics but no backlight before?

Is the video cable to the lcd removable?

If yes, remove the lcd from the cable. Using only the lcd cable attached to the logic board, power up. Any chime?

If the cable is not removable, remove all power.

Meter in resistance mode.

Check the resistance to ground of each pin on the lcd connector. Compare the results to the lcd connector schematic.

Some pins will be ground, some power, some signals.

Do review the ferrite beads that are used to clean up the signal lines to the lcd display. Are they all there? No corrosion?

Something is killing the lcd activity. Check for a lcd fuse connected to the lcd panel connector. Will review once at the office.

[Gigabit2]

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

Have you ever seen the lcd show you the apple logo or similar? I think you had graphics but no backlight before?

Yes, very briefly yesterday it was working, then during usage it went black and has been that way since. Backlight was working then.

Also update, it does chime when display is connected but shows no video nor backlight on the display. I had not connected the speaker before.

Check the resistance to ground of each pin on the lcd connector. Compare the results to the lcd connector schematic.

Pins 2 and 3 looking ok, .008 on 2V mode to ground and when powered on showing 3.3V which is as expected.

Pin 4 also showing .008 on 2V mode. 3.3V when powered on.

Pin 6 showing .013 on 2V mode, showing 3.3V when powered on.

Pin 7 showing .010 on 2V mode, showing 3.3V when powered on.

Pin 8 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 9 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 11 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 12 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 14 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 15 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 17 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 18 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 20 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 21 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 23 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 24 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 26 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 27 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 29 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 30 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 31 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 32 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 33 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 34 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 35 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 36 showing .000 on 2V mode, showing 0V when powered on - shorted?

Pin 38 showing .000 on 2V mode, showing .016V when powered on - shorted?

Pin 39 showing .000 on 2V mode, showing .016V when powered on - shorted?

Pin 40 showing .000 on 2V mode, showing .016V when powered on - shorted?

Do review the ferrite beads that are used to clean up the signal lines to the lcd display. Are they all there? No corrosion?

Can you help me locate these?

Something is killing the lcd activity. Check for a lcd fuse connected to the lcd panel connector. Will review once at the office.

Can you help me locate this?

Is the video cable to the lcd removable?

If yes, remove the lcd from the cable. Using only the lcd cable attached to the logic board, power up. Any chime?

Cannot remove cable to the LCD. But as mentioned, do get chimed when LCD connected. Just no video or backlight.

Many thanks for all your help so far mon2.