820-01041-A - Works only when battery disconnected

[GoodguyFR]

Hi there,

Historic : it has been liquid damaged on the very right side, only the tests points near U8800, U8700, U8600 and U8900 were corroded, some of them are gone. Nothing more seems to be damaged, but liquid could have been through more components.

Behavior : the board works fine when battery is not connected, I have been able to backup data. But when battery is connected, the fan start to spin for 20 seconds, no chime nor image, and out of the blue the fans go full speed for one second and the Mac shuts off. It does it in loop.

Tried so far : I started with battery and battery cable swap with a known good one, same behavior. Removed J4801 that looked bad, don't know why I did that...

Do you have any guess ? It's the first time I see something like this. Any help is welcome, thank you for your time.

 

[2informaticos]

You need to connect both J4800/01 to get correct lid signals.
If not, problem appears when you put machine in sleep state, closing the lid.

What is exact PPBUS_G3 voltage, when battery is connected?
Check w/ and w/o charger connected.

 

[GoodguyFR]

Ok It's understood for J4800, I'll fix this later.

Regarding PPBUS voltage when battery is connected, here is the 2 different behaviors :

W/O charger : start at 11V, stay at 11V until fans go full speed, and when it happens PPBUS jump to 11,45V for 2 sec, and go back to 11V

W charger : start at 11,8V, ramp slowly to 12,1V, then fans go full speed, when it happens PPBUS jump to 12,4V, and go back to 11,8V

 

[2informaticos]

Check resistance over C7020/23.
Inspect for corrosion around U7000.

 

[GoodguyFR]

Resistance over these caps are ok, around 3Ohms. I noticed U7000 was a bit crooked, I reflowed it, it went back in place. After new test, problem remains.

 

[2informaticos]

Then change U7000.
Check SMC_DCIN/BMON_ISENSE and SMC_DCIN/PBUS_VSENSE; w/ and w/o battery connected (charger present, of course).

 

[GoodguyFR]

Hi 2informaticos,

I replaced U7000, it was clean underneath, and the Mac still has the same behavior.

Here are the DCIN sensors values :

With battery :

• V sense = 1,05V
• I sense = 0,45V at the beginning, ramp to 0,6V until it shut off, and back to 0,45V

Without battery :

• V sense = 1,05V
• I sense = 0,21V

 

[2informaticos]

What's the exact PPBUS_G3H with only adapter connected?
Check diode mode to ground at SCL/SDA lines of battery bus; before and after Q6950.

 

[GoodguyFR]

The exact PPBUS_G3H is 12.4V when there is only adapter connected.

Regarding SCL/SDA lines :

SMBUS_3V3_BATT_SCL = 1.18
SMBUS_3V3_BATT_SCA = 1.16

I2C_PWR_SCL = 0.47
I2C_PWR_SCA = 0.47

Usually, 12.4V means bad SMC or bad communication with it right ?

 

[2informaticos]

Yeah, looks like no communication between T2 and U7000.
Try changing U7000.

 

[GoodguyFR]

As I already changed U7000 previously without any change, maybe the problem comes from the T2 Chip. Does a reflow worth the try ? Is there a tool to reflash these thing as we can do with BIOS and Medusa ?

 

[2informaticos]

"SMBUS_3V3_BATT_SCL = 1.18
SMBUS_3V3_BATT_SCA = 1.16"
Check them in proper way; red probe connetced to ground!

 

[GoodguyFR]

These numbers have been rounded but they are correct. I give you the exact value :
SMBUS_3V3_BATT_SCL = 1.181
SMBUS_3V3_BATT_SCA = 1.155

 

[2informaticos]

I never saw such high values in diode mode.
Did you really check with black probe there and red on ground?
Be sure to switch multimeter to diode, not ohm scale.

 

[GoodguyFR]

I am 100% sure, using the same multimeter for years now. But it is not the first time I see such high values in diode mode, isn't it supposed to be in a range from 0v to 2v ? Looks correct to me. Do you have a 820-01041-A board to compare values with me ?

 

[2informaticos]

I just checked schematic again; no board available here for comparison.
However, high values should be good, being on the battery side; separated by the rest with Q6950.
Remove U6950 and test the board again (w/o battery).

 

[GoodguyFR]

Hi 2informaticos,

Thank you for your time, I had to give the MacBook back to the customer as I was not able to find the problem quick enough. We'll never no what was the problem on this one.

We can close this thread.
See you soon