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

[mon2]

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

What is the voltage of PPVCORE_S0_GFX_REG ? (with LCD connected)

[Gigabit2]

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

Mon2, with power on?

[Gigabit2]

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

Do you have a test point for PPVCORE_S0_GFX_REG?

[mon2]

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

Yes. See attached. Yes, with power on - need to see if the power rail for the GPU is working.

[Gigabit2]

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

Measuring 0.89 on 20V mode, tested with C9861, C9862, C9863, C9864, all showing same

[mon2]

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

Voltage for this power rail is OK.

What are the voltage readings for the following (with LCD & powered on)?

LCD_PWR_EN
PP3V3_S5_LCD
PP3V3_SW_LCD

See attached.

[Gigabit2]

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

LCD_PWR_EN tested at R9094 showing .013 on 2V mode.

PP3V3_S5_LCD tested at C9009 showing 3.31 on 20V mode.

PP3V3_SW_LCD tested at C9002 showing 00.2 on 200m mode.

[Gigabit2]

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

Hi mon2,

Hope you are having a nice weekend. When you get some time, please can you review the above. No hurry.

[mon2]

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

Hi. Do not have this board here but here is what I believe may be happening..

< just review as random thoughts in my head on this case >

1) this logic board is known to have GPU issues and was built with AMD & NVIDIA video chipsets. The AMD GPU was the flaky one and NVIDIA was apparently much improved with only a few faults.

2) there are assorted articles (by DOSDUDE) on how to disable a defective GPU use but do not believe this is your case since the HDMI external video is working OK. The chart on page

3) instead, suspecting the fault is with the video MUX (multiplexer) @ U9600. Think of the MUX has a multiple SPDT solid-state switches that route a group of signals from a single source to either position of 'A' = HDMI side or 'B' = LCD side.

4)

LCD_PWR_EN tested at R9094 showing .013 on 2V mode.

LCD_PWR_EN is created by N8 ball on U9600 BGA device.

5) U9600 is a Lattice FPGA = empty and blank chip if purchased new from Lattice Semiconductor and a JTAG programmer is used to reflash it with custom code (IP) to make it do the function you would like. From a brief review, DOSDUDE sells a single use license to bypass the MUX but you can Google for more information or even ping him - I believe that we contacted him a few years ago and he was very helpful and was working off donations back then. We did donate and just charged our customer for the fix & donation. That is our only experience with this model to date.

Believe an idea is to hunt down a donor board -> remove this U9600 and replace on this non-working board since the donor board will have a programmed FPGA device. Highly recommend to email DOSDUDE for advice with the summary of this thread. HDMI video works / LCD remains dark. Mention that the above LCD_PWR_EN is LOW and this is driven by the same Lattice FPGA acting like a MUX.

Respectively, if the HDMI half of this FPGA is working - is this FPGA considered defective ?

BANK7 of U9600 pins = INPUT from GPU

BANK0 of U9600 pins = LCD display output signals

But do review the assorted other muxes linked to the video flow on page 86 (Muxed Graphics Support) of the schematics.

Is there a defect here ?

Wait on more feedback from others and certainly ping DOSDUDE1 for his comments. He has at least one video on Youtube about the mux but do not believe it is your case - he mentioned about the loss of the power rail for the GPU which you have confirmed is ok @ 0v9. His case had 0v for the GPU power.

Will review more after a Costco run...

[Gigabit2]

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

Would anyone else care to assist? Thank you to @mon2 for all their help thus far

[mon2]

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

What is the power rating of your magsafe power supply that is being used for these tests ?

1) Given that this logic no longer posts if the LCD display is attached - the cable or display are strapping the motherboard.

2) In reviewing again, page 2 of the schematic, the logic flow is:

a) external video is driven by the NVIDIA GPU - if the external video is stable then the GPU is fine as you posted earlier

b) the GMUX @ U9600 takes input from the dedicated GPU (NVIDIA) or the INTEL internal video controller and routes it to the LCD connector @ J9000.


Post the voltage readings for the following:

PP1V2_S0_GMUX

PP1V8_S0_GMUX

PP3V3_S0_GMUX

PP3V3_S0_GMUX_R

PP3V3_S3_GMUX

GMUX_S3_PD_GND

ALL_SYS_PWRGD

LCD_BKLT_PWM (before R9704)

BKL_PWM (after R9704)


See attached for reference. You can measure at any of the highlighted parts for the respective power rail.

Confirm the resistance of resistor @ R9714. This resistor value is critical to configure the max current that the backlight power supply will support for the boosted power rail.

[Gigabit2]

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

Hi mon2,

It is 85W. Also used another adapter and a USB-C to MagSafe converter connected to an 85W supply and the same issue occurs.

PP1V2_S0_GMUX: 1.2V with 20V mode
PP1V8_S0_GMUX: 1.8V with 20V mode
PP3V3_S0_GMUX: 3.32V with 20V mode
PP3V3_S0_GMUX_R: 3.32V with 20V mode
PP3V3_S3_GMUX: 3.32V with 20V mode
GMUX_S3_PD_GND: 2.64V with 20V mode
ALL_SYS_PWRGD: 3.28V with 20V mode
LCD_BKLT_PWM (before R9704): 0.08 with 200m mode
BKL_PWM (after R9704): 0.08 with 200m mode

Resistance of resistor @ R9714: 16.1 with 200k mode

[mon2]

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

Post the voltage on each side of R9676.

[Gigabit2]

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

Pin 1: 3.32 with 20V mode
Pin 2: 00.5 with 200m mode

[mon2]

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

In the 2nd pic above, there are numerous resistors in the schematic.

Measure and post the voltage readings on each side of the resistors.

Be very careful as the parts are small.

From a similar thread on Louis' forum, the GMUX_S3_PD_GND value on your board is low as compared to another tech who reported 3v0.

[Gigabit2]

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

R9678

Pin 1: 0.13 with 200m mode
Pin 2: 2.65 with 20V mode

R9671

Pin 1: 3.32 with 20V mode
Pin 2: 2.64 with 20V mode

R9672

Pin 1: 3.32 with 20V mode
Pin 2: 2.64 with 20V mode

R9673

Pin 1: 3.31 with 20V mode
Pin 2: 2.64 with 20V mode

R9674

Pin 1: 3.32 with 20V mode
Pin 2: 2.64 with 20V mode

R9675 - not present

2.64 on one side with 20V mode, 0.00 on other (as expected with nothing present)

[mon2]

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

(from another forum so it is censored)

is related to your case.

If I understand the translation correctly, suggest is to reflash the mux at U9600.

[Gigabit2]

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

Hi @mon2, how would I go about doing this? Which tools would I need?

[Gigabit2]

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

@mon2, is there no issue with R9678? Not boosting to 3.32V, as other resistors are?

[mon2]

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

No, R9678 is ok but is an output enable signal from the mux chip by Lattice (U9600). The output is low.

You will need a JTAG programmer. More details after some research on this topic.