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

Hi mon2,

So some good news!

I gave area around U9600 wipe with rubbing alcohol 70% and external display now working with LCD connected! But internal display still showing nothing including no backlight.

Pin 1, 2, 3 showing 3.3V when internal LCD connected now. So I wonder if was some corrosion around U9600 that I have removed with alcohol?

This is a great start but sadly internal screen still not working. But moving in right direction???

[mon2]

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

R9682 showing as 9.92

What is the meter scale ? This resistor should be ~10k ohms which it appears to be but please confirm the meter scale.

Yes, when external HDMI / DP port is used, Rossman's forum states that the dedicated GPU is used so we know that it is working fine. For this reason, avoid the DOSDUDE1 mux firmware unless we can reverse the operation. The key reason being that we do not want to disable the only known working video source = GPU !!

Any chance that DOSDUDE1 has the (IP) firmware to restore the FPGA operation to factory ?? This will be a nice to have to correct any possible firmware corruption. Just a thought.

On this note, is the internal graphics function damaged or is it linked to the detection of the LCD or the muxes are not working properly.

Will continue to review.

[Gigabit2]

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

Yes scale is 20k for resistor

[Gigabit2]

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

Okay even better news.

I plugged in original display for MacBook (not test display) and display is now showing something!

[Gigabit2]

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

Okay is displaying white image and backlight on. But not showing any OS or question mark without HDD plugged in.

Where next?

[mon2]

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

Post a pic of the lcd that has backlight working.

No graphics can be seen?

Take measurements at the lcd connector while this is working. Very carefully.

[Gigabit2]

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

J9000 tests:

Pin 1: GND
Pin 2: 3.3
Pin 3: 3.3
Pin 4: 3.3
Pin 6: 3.3
Pin 7: 3.3
Pin 8: 0.82
Pin 9: 0.92
Pin 11: 0.82
Pin 12: 0.92
Pin 14: 0.82
Pin 15: 0.82
Pin 17: 0.82
Pin 18: 0.82
Pin 19: 0.82
Pin 20: 0.82
Pin 21: 0.93
Pin 23: 0.82
Pin 24: 0.92
Pin 26: 0.92
Pin 27: 0.92
Pin 29: 0.92
Pin 30: 0.92
Pin 31: 0.65
Pin 32: 0.85
Pin 33: 0.65
Pin 34: 0.84
Pin 35: 0.67
Pin 36: 0.89
Pin 38: 31.8
Pin 39: 31.8
Pin 40: 31.8

[mon2]

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

Now replace the LCD with the one that remains dark and measure again. Post the results so we can compare the readings.

[Gigabit2]

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

But mon2 there is no graphic displayed on the "working" (i.e. backlight on) monitor. Is not showing any image beyond white screen

[mon2]

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

Post the voltage readings for the GMUX FPGA (CPLD).

no graphic displayed on the "working"

Understood. The signals for the LCD are linked to the GMUX FPGA / CPLD. Hence the request in the last post - is the GMUX being powered ? Is it damaged and not routing the video signals ?

Perhaps you can ask DOSDUDE1 on how to force the GMUX FPGA to drive the LCD ? Specifically, which pin on the GMUX is used to send video data to the LCD?

It is also possible that the source of the video = Intel chipset(?) is not working but always thought that the GPU (AMD) were the most flaky and NVIDIA were the fixed versions of this fault.

[Gigabit2]

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

Here is what I see on "working" monitor:

[Gigabit2]

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

C9628: 3.3v
C9631: 3.3v
C9630: 3.3v
C9609: 1.12v

[mon2]

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

So the GPU MUX is being powered ok. Good.

What voltage readings do you see on each side of the resistor that is highlighted ?

These are the clock pins from the INTERNAL graphics controller fed by PANTHERPOINT IC @ U1800.

Interested to know voltage of:

LVDS_IG_A_CLK_N
LVDS_IG_A_CLK_P

which are best to be probed at the termination resistors shown in the attachment.

Comment : These are LVDS signals = low voltage; differential signals so it is fair game that the voltage readins are as you are measuring. For very high data rates like LCD displays, the LVDS signals transition to high / low very quickly and for this reason, they keep the voltage amplitude down but use a positive and negative polarity. The difference between the 2 lines defines what is a high or a low.

[Gigabit2]

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

Showing 02.0 on 200m mode.

[mon2]

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

I think that neither of us have the proper tools to measure the very high speed; very low voltage signals used by the LVDS LCD display.

I had hoped that there would be a clear difference between the voltage of the signals that ENTER the GPU MUX and what LEAVE the GPU MUX so still confused.

Remove all power. Meter in resistance mode.

With the LCD that shows the BACKLIGHT -> what is the resistance across pins 17 & 18 ?

What is the resistance across pins 29 & 30 ?

To confirm, this display 'works' with the backlight but no graphics. The 2nd display does not have a backlight even ? Believe you have said this one did work to show the backlight & graphics but no longer for both ?

Switch to this 'non-working' display and measure the above resistance values.

[Gigabit2]

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

This board now turning out to be real disaster

Previously working display now also just showing black. No backlight anymore.

[mon2]

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

Continue to use the display that had a working backlight.

Remove all power and measure the resistance to ground of PPVOUT_S0_LCDBKLT - with the LCD connected. What is the reading ?

[Gigabit2]

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

.485 on 2m mode

[Gigabit2]

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

Backlight has come back on "working" monitor. Re-seated cables.

[mon2]

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

Could your LCD connector be flaky / Kim Kardashian loose ?