Macbook Pro A1286 820-2850-A

[John_F_L]

Hello everyone,

I have a macbook pro a1286 with 820-2850-a motherboard and my problem is this. When I power on the laptop, I hear the chime and then it shuts off. I have green or orange light on the charger. I have also tried another charger.
Also I have reset the smc and all the things that Apple says.
After I took the board out I saw that the isl6295 was getting really hot so I replaced it with a new one. Now it doesn't get hot but the same thing happens.
What else shall I try?

Thank you.

[audiomodder]

Re: Macbook Pro A1286 820-2850-A

do you mean ISL6259? This is a common failure, especially if any liquid damage.

What is your voltage for PPBUS_G3H? measure it until shutoff..
More importantly, use a 30X or more magnifier (or microscope) to inspect the area of that part. Sounds like your current sensing passives are going bad, though it could be a few issues.

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

after a lot of searching on the board I found out that it won't start when the LCD is connected. If I remove the LCD the macbook boots (I can see it on my bench supply).
I checked all the pins on the connector, I cannot find any short. I have already tried another LCD with cable and the same thing happens.

[audiomodder]

Re: Macbook Pro A1286 820-2850-A

OK, please see my above post and answer the questions. Need to know if there was water damage and your voltage rails.

The LCD communicates with GPU and also is supplied its own voltage (pins 3-4 IIRC). If the GPU doesn't "see" your LCD, i.e communicate with it, you are going to have problems.

was the GPU ever reflowed? Did the computer get too hot and shutoff at one point?

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

I cannot see any sign of liquid damage at all.
The PPBUS_G3H is 11.7-11.8 until shutdown which goes to 10.5.
Under the microscope I cannot see anything that seems weird.

As for the GPU, as far as I know, noone has ever reflowed it. But because it is a customers laptop I'll never be sure about that.

I forgot to mention that I have a green light on the charging cable (it won't go orange because i supply the laptop from my bench DC power supply), but the battery charges.

Also if I remove the board from the chassis, the fan spins high all time and the PPBUS_G3H is 12,4 to 12,5 all the times

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

This MacBook is going to get me crazy. Right now I have 12,46V when it is power on and when it shuts down it is going to 1.5V-1.6V.

[audiomodder]

Re: Macbook Pro A1286 820-2850-A

"The PPBUS_G3H is 11.7-11.8 until shutdown which goes to 10.5."
sounds like something is wrong there. It should ALWAYS be ~12.6V. When you say "remove from chassis" - you mean remove LCD?
Sounds like maybe your PPBUS_G3H step up converter (for backlight voltage) is fried.

Check Q9806, Q4260, U9701, U7790. Check PPBUS_S0_LCDBKLT_PWR for shorts.

LVDS issue can also be:
1) wrong screen / wrong year (2012 needs to match)
2) Bad LVDS connector
3) short on LVDS lines
4) missing CLK and data lines for LVDS detect
5) bad GPU (failed reflow, overheat, etc.)

do you get 3V3 on the LVDS connector? Are you looking things up with the schematics?

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

When I say remove from chassis, I meant when I have the motherboard on the bench without anycable connected.
The LCD is the original one
I have the same laptop from another customer
LVDS lines are not in short.
On LVDS connector pin 2-3 I don't get the 3V3. (LCD Disconnected)
Also on Q9806 I get 11,7V on pin 3, 12,4 pin 4 and 0V on 1,2,5,6.
Q4260 4,5 on pin4 and 12,02 on all other pins.
U9701 almost all of the pins are 0 but I get the PP3V3_S0.
U7790 I don't have it on my board or boardview.
What else is a bit weird is that If I connect just the DC power supply (oem cable) without the battery PPDCIN_G3H on R7020 is starting from 18V and going down to 1,5 because the gate on q7085 is 17V instead of 7V.

I searched a bit why I don't have power on LVDS and I found that on Pin1 of U9000 I have 0V and 10Kohm Resistance to ground on the same pin.

[audiomodder]

Re: Macbook Pro A1286 820-2850-A

OK well pin 1 on U9000 is an enable pin, it needs go high (3v3 probably) before you will get anything on the output.

Im assuming you are taking these measurements when it is off. Pin 1 is GND when the system is off?

you can remove U9000 and see if LCD_PWR_EN (pin 1) is still a short to GND. If it is, then it looks like something with U9600 maybe. Before checking that, check Q9607 and R9678 for shorts.

your U7000 chip sounds messed up, probably DCIN sense resistor circuit (2x 10ohm and 0.047uf). If it runs well on battery but not DCIN thats usually the issue.

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

U7000 has been changed with a new one. But I'll order and replace it one more time (I don't have another one)
U9000 is not short to ground except pin6 which is GND. All the measurements are when the laptop is on but without having connected the LVDS.
I also tried a good reflow on the VGA but nothing changed.
I'm assuming that the SMC has gone bad but I don't have a new one and also it is not that easy to find in Greece another one. And also don't have a stencil to replace it with a used one.

[audiomodder]

Re: Macbook Pro A1286 820-2850-A

you need to check the passives around U7000, not just the chip. do you have pics?

stop reflowing things...this is a bad idea. You are getting a chime and you have many other things to check before reflow. I know, I killed a macbook GPU years ago when i thought reflow was the answer to everything.

Nothing here indicates bad SMC. watch louis rossman videos and familiarize yourself with the logic board. If you are getting a chime then your SMC is OK. you obviously have a power related issue and need to inspect that area carefully and the rails.

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

I'm uploading some photos from the motherboard from both sides. I checked the passives around the U7000 area and none of them seems broken or anything. Also with the multimeter I cannot find anything that shorts to ground.

[audiomodder]

Re: Macbook Pro A1286 820-2850-A

OK tell me exact voltages for:
PBUS_G3H
LCD_PWR_EN
PP5V_S3
PP3V3_S3
PP1V5_S3
LVDS_DDC_CLK
LVDS_DDC_DATA

then maybe:
BKLT_PLT_RST_L
LCD_BKLT_EN

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

the voltages are (with battery connected because without the battery the motherboard won't start all the times)
PPBUS_G3H - 12.48V
LCD_PWR_EN - 0V
PP5V_S3 - 4.98V
PP3V3_S3 - 3.28V
PP1V5_S3 - 1.48V
LVDS_DDC_CLK - 3.26V
LVDS_DDC_DATA - 3.26V

BKLT_PLT_RST_L - 3.26V
LCD_BKLT_EN - 0V

[audiomodder]

Re: Macbook Pro A1286 820-2850-A

OK good. sounds like you have 2 issues:
1) bad charging circuit somewhere
2) LCD issue (which could be a number of things)
lets fix the charging circuit first.

What is:
CHGR_ACIN
SMC_BC_ACOK

resistance values for:

R6929
R7021
R7022
R7051
R7052

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

I accidentaly shorted the ISL6259A to ground so I'm waiting for a new one.
the resistance values are:
R6929 - 2k
R7021 - 10.8Ω
R7022 - 10.8Ω
R7051 - 17.3Ω
R7052 - 0.3Ω

[John_F_L]

Re: Macbook Pro A1286 820-2850-A

The new ISL came in today, i replaced it and now I don't have green light and the mac won't turn on even with the battery. I tried two of them.
CHGR_ACIN is 4.3V and the SMC_BC_ACOK is 0V. On the other side of the R7010 (PPDCIN_G3H) I have 18.5V.

[vinifera]

Re: Macbook Pro A1286 820-2850-A

can we simulate the input 1 on the U9000 to generate the 3.3V on the PP3V3_SW_LCD ?

[fernd10]

Re: Macbook Pro A1286 820-2850-A

Hi all i have a 820 2533-b and need help it running well but randomly shuts down any ideas to old could be out dated ?