First post - A1502 won't start after water damage

[dongfang]

Hi all,

Thanks you for making this possible!

I have messed with and designed electronics for long, but this is the first time I am facing a Macbook repair.

Story is: Cold A1502 met a moist environment in a bag, then made sizzling noises as it was turned on. I took it apart, and found the keyboard backlight connector molten right in half, and the display connector (J8300) having some serious corrosion around the Pin 30 end with the 3V3 supply.

I unsoldered the keyboard backlight connector and cleand up the diosplay connector the best I could, hoping I would not have to tear apart the display and replace the LVDS display cable. Plugged it back together, stupidly reconnected the battery and powered it on. There was a short in J8300, the pin 30 end started glowing white, but apart from J8300 and the display cable, nothing seemed damaged.

I have unsoldered J8300 completely now, but the computer won't turn on at all. Draws 10mA as fed from a DC supply. Also does nothing on an original Magsafe adapter. PP3V42_G3H is present. The hope is that I can get it to work on external HDMI display and let me recover some data, until I get a new display connector and cable.

So my newbie questions are:

1) What's the minimum equipment that must be connected to the main board to get it to draw some amps and try start up? SSD needed? Fan needed? Display needed?
2) When I short R5116 to simulate the power key being pressed, the magsafe plug goes from green to orange, but current does not increase. When I short R5101, it returns to green. Is that indicative of anything? To me it seems that it's now about the usual suspects in the comms with the power supply.
and 3) There are 3 individual connections entering the magsafe connector from the computer side, but only 2 wires in the cable. And there are 2 LEDs too. Does that thing really have a power MOSFET in the connector itself? Craaaazy if it does.

EDIT after some more measuring:
PP3V42_G3H present, 3.44V
PP3V3_S5 present, 3.33V
PP5V_S5 5V
PPBUS_G3H present, 12.59V
PP5V_S4 not shorted to GND
PPBUS_S5_HS_OTHER3V3 not shorted to GND
PPBUS_S5_HS_OTHER5V not shorted to GND
PPBUS_S5_HS_COMPUTING not shorted to GND
PPVCC_S0_CPU_PH1 not shorted to GND
PP3V42_G4H not shorted to GND
F7140 0 Ohm

P5VS4RS3_EN is low


PP3V42_G4H is 0V .. so the PWROK stuff around U1950 is all low.

Keyboard backlight power connector has a track PPVOUT_S0_KBDBKLT corroded away, but that shouldn't prevent startup?

U8300 SLG5AP1443V, display power switch: 5V track to it still has good connection to both ends of MLB. Part is not blown up.

There is no "fan spin" when connecting power, but I believe an A1502 isn't supposed to do a fan spin anyway?

Main problem remains: I seem to have all the S5 voltages just fine, but nothing wants to come on when pressing power button. Unlike Louis in this vid about the same topic:

, I have not found any supply rail shorted to ground.

Kind regards, Soren

 

[dongfang]

Hi all,

Thanks you for making this possible!

I have messed with and designed electronics for long, but this is the first time I am facing a Macbook repair.

Story is: Cold A1502 met a moist environment in a bag, then made sizzling noises as it was turned on. I took it apart, and found the keyboard backlight connector molten right in half, and the display connector (J8300) having some serious corrosion around the Pin 30 end with the 3V3 supply.

I unsoldered the keyboard backlight connector and cleand up the diosplay connector the best I could, hoping I would not have to tear apart the display and replace the LVDS display cable. Plugged it back together, stupidly reconnected the battery and powered it on. There was a short in J8300, the pin 30 end started glowing white, but apart from J8300 and the display cable, nothing seemed damaged.

I have unsoldered J8300 completely now, but the computer won't turn on at all. Draws 10mA as fed from a DC supply. Also does nothing on an original Magsafe adapter. PP3V42_G3H is present. The hope is that I can get it to work on external HDMI display and let me recover some data, until I get a new display connector and cable.

So my newbie questions are:

1) What's the minimum equipment that must be connected to the main board to get it to draw some amps and try start up? SSD needed? Fan needed? Display needed?
2) When I short R5116 to simulate the power key being pressed, the magsafe plug goes from green to orange, but current does not increase. When I short R5101, it returns to green. Is that indicative of anything? To me it seems that it's now about the usual suspects in the comms with the power supply.
and 3) There are 3 individual connections entering the magsafe connector from the computer side, but only 2 wires in the cable. And there are 2 LEDs too. Does that thing really have a power MOSFET in the connector itself? Craaaazy if it does.

EDIT after some more measuring:
PP3V42_G3H present, 3.44V
PP3V3_S5 present, 3.33V
PP5V_S5 5V
PPBUS_G3H present, 12.59V
PP5V_S4 not shorted to GND
PPBUS_S5_HS_OTHER3V3 not shorted to GND
PPBUS_S5_HS_OTHER5V not shorted to GND
PPBUS_S5_HS_COMPUTING not shorted to GND
PPVCC_S0_CPU_PH1 not shorted to GND
PP3V42_G4H not shorted to GND
F7140 0 Ohm

P5VS4RS3_EN is low


PP3V42_G4H is 0V .. so the PWROK stuff around U1950 is all low.

Keyboard backlight power connector has a track PPVOUT_S0_KBDBKLT corroded away, but that shouldn't prevent startup?

U8300 SLG5AP1443V, display power switch: 5V track to it still has good connection to both ends of MLB. Part is not blown up.

There is no "fan spin" when connecting power, but I believe an A1502 isn't supposed to do a fan spin anyway?

Main problem remains: I seem to have all the S5 voltages just fine, but nothing wants to come on when pressing power button. Unlike Louis in this vid about the same topic:

, I have not found any supply rail shorted to ground.

Kind regards, Soren

Update:

Well I have measured about everything I could get at, which I see as relevant for powerup. Nothing defective found. Fuses are good, most MOSFETs are good, clock generator outputs a 32KHz clk even in powerdown.

I have discovered that about one every 5 times, at power plug in, it actually starts up. It draws (no battery connected) about one amp for about 20 seconds, then turns itself off. This is with the naked motherboard on the table, only the fan and the power adapter connected to it. No display, no right side logic board, no battery. No SSD even.
- It does not play a bong in the speakers. when I connect them.
- It does deliver 5V do the fan, but no PWM attempt to get it to run.
- The original damage was a short circuit to GND of the 5V out circuit on the LVDS connector. It seems to have survived that.

What is the normal behavior for my A1502 on powerup without SSD and without anything connected? Shouldn't it at least spin the fan? Will it be able to accept power for 20 seconds and then turn off if the CPU is dead?

Kind regards, Soren

 

[Sanpete]

Have you also posted this at iFixit? Looks like they'd be more knowledgeable about it.

 

[dongfang]

Hi Sanpete, thnak you - no, instead I have wasted my time waiting for confirmation emails that take forever to arrive over at Rossmann .. but anyway, I got it, I need to go elsewhere. I use this thread for my own notes now...
Kind regards, Soren