A1286, 820-2850-A , no water damage, no detect battery...

luk812

Member
Hello , I have a problem with SMBUS_SMC_BSA_SDA have short to ground with magsafe connected.....

The macboook pro boot to OSX , but no detect battery.(battery is new).

I have low voltage (with magsafe only) on Pin 2 of R5280=0,60V to 0V, I decide to desoldering R5280.

R5280 & R5281 are Ok
(probably ,because on pdf '' K18_820-2850 A1286'' , R5280 & R5281 display 1 KΩ but they have 2KΩ on board (after desoldering) ).


So SMBUS_SMC_BSA_SCL is OK.


SMBUS_SMC_BSA_SCL-1.png




SMBUS_SMC_BSA_SDA without magsafe:
SMBUS_SMC_BSA_SDA-1.png


SMBUS_SMC_BSA_SDA with magsafe:

SMBUS_SMC_BSA_SDA-2.png




U7000 / ISL 6259!!! replace by new.---------
 
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luk812

Member
PPDCIN_G3H short to ground with magsafe, I have desoldering Q7080,D7005,(+U7000,D6950).

Pin 5.6.7.8 of Q7080 have Short to GND.
I have no idea why PPDCIN_G3H have short, I try to follow the pdf, inspected the board.....
I think that the short to gnd is beetween F6905 and Q7080(pin 5.6.7.8)+D7005 (pin 1.2).
(and desoldering F6905= no short beetwween ''MagSafe DC Power Jack'' and ''Fuse''.

C6905 OK
short.png





bad SMC?
 
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larossmann

Administrator
Staff member
Why are you doing that? You realize that this not only won't provide you with a proper measurement but will also kill your multimeter?
 

luk812

Member
OMG.......:(......
Now I realize.
So sorry for my mulimeter (and make you lose time, I hope you have a good laugh !!!)!!!!!!!!!!!!!!!!! Now I never it again, so applied power with multimeter on diode mode..................



**************************************************
************************************************** *****
I resolder the components and make mesures for you see....
 

G.Beard

New member
OMG.......:(......
Now I realize.
So sorry for my mulimeter (and make you lose time, I hope you have a good laugh !!!)!!!!!!!!!!!!!!!!! Now I never it again, so applied power with multimeter on diode mode..................



**************************************************
************************************************** *****
I resolder the components and make mesures for you see....

Multimeters make measurements (simplest form) based on volatge drops across resistive paths. A multimeter trying to measure a drop accross a path that has applied voltage will therefore give you the wrong readings. Google for ohms law and you'll get why. Sorry if you already know this stuff.
 

luk812

Member
So I have resoldering components.....
So I mesure rails....

PPBUS_G3H=1.60V
1471606190-ppbus-g3h-1-60v.jpg
PPBUS_CPU_IMVP_ISNS= 0.60V
1471606197-ppbus-cpu-imvp-isns-0-60v.jpg
and I mesure PPDCIN_G3H:
1471606225-spark-appear-2.jpg

1471606221-spark-appear.jpg

(no boot, no fan...)
 

luk812

Member
So now PPDCIN_G3H was low voltage, I decide to desoldering F7040 (always low voltage)
I desolder U7000, and PPDCIN_G3H= 17V
Now mesures of resistance around U7000:


1471606509-u7000-mesures.jpg


So I must replace R5280, R5281 (1.985Ω)????

replace R7015(56.5KΩ)?
replace R7005(4.81KΩ)?
 
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larossmann

Administrator
Staff member
Do not touch R5280/R5281!

If R7005 if anything over 20 ohms, replace R7005 & U7000.

R7015 is only measuring lower than 220k because there are other items in the circuit around it, do not touch.

Lastly as always measure voltage between pins 17/18 and 27/28 of U7000 when you are done with all of this. Usually between pins 17/18 there is a break from top of the board to bottom of the board on the 2850 that causes problems.
 

luk812

Member
R7005 & U7000 replace....
I have desoldering C7015 and the capacitance = 1010pF, normaly 470pF...., must I replace too?( all SMD ceramic capacitors around U7000 are ok except C7015 ...)
 

luk812

Member
Replace C7015, R7005 & U7000.
Green light reappear
U7000:
PIN 17=12.20V
PIN 18=12.20V
PIN 27=16.55V
PIN 28=14.55V

Replace F7040:
green light ok, fan boot ok....

U7000:
PIN 17=12.22V
PIN 18=12.22V
PIN 27=16.70V
PIN 28=16.75V
 
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luk812

Member
After few minutes, PP3_G3H very low...=0.40V.

Green light ok, no fan, no boot now.




F7040 desoldering.png
 
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luk812

Member
Hello!
I have green light , fan high speed, no chime,no video.

PPBUS_G3H OK
PPBUS_CPU_IMVP_ISNS OK
PPDCIN_G3H OK
PP3V42_G3H OK



PPVCORE_CPU ok

PPVCORE_GPU OK

PP3V3_SW_LCD voltage= 0 Volt.
PP3V3_SW_LCD.png





PP3V3_SW_LCD-2.png




F9800 is OK with 12 Volts.

LCD_BKLT_EN = 0 Volt.....
LVDS_DDC_CLK = 3.3V
LVDS_DDC_DATA=3.3V

U9600 problem????

An idea please?
 
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