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820-4924 - initially show folder and no backlight but fixed with new problem.

Alan.L

Alan.L

Member
board is water damaged. initially show folder and no backlight, so i've replaced the LCD connector and had to run a wire as there was damage on the PPVOUT_S0_LCDBKLT pin.

initially show 12v on PPVOUT_S0_LCDBKLT pin but then 0v after i replaced the u7700 which i got from a donor board.
and i've made it worst than before. now system doesn't turn on automatically. open way to turn on is SMC bypass.

i then put back the original u7700 and still no dice. did i killed something else?


PPBUS_G3H = 12.56V
PPBUS S5 HS COMPUTING = 12.56V
PPBUS S5 HS OTHER3V3 = 12.56V
PPBUS_S5_HS_OTHER5V = 12.56V
PPBUS_S4_X239 = 0V
PP3V42_G3H = 3.42V
PP5V_s5 = 5v
PP5V S4 = 0v
PP3v3_s5 = 3.3v
PP3v3_s4 = 0v (SMC bypass 3,3v)
PP3v3_s3 = 0v (SMC bypass 3.3v)


i then looked at the Q7701 & Q7700 fets and swapped these two out and ta-da!!! Backlight is revived. but still the only way to turn on is SMC bypass.
 
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Alan.L

Alan.L

Member
85w original apple, sorry i ment PPVOUT_S0_LCDBKLT now has 50v.

my screen is working now, just having SMC bypass to turn on problem. which i didnt have before the repair. only occurred after i changed u7700.
 
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D

dukefawks

Administrator
Do you get the green light and then orange after a few seconds? If yes then also check resistance between pin 17/18 and 27/28 of the ISL6259.
 
Alan.L

Alan.L

Member
yes.

4 ohms on pin 17/18
20.5 ohms on 7/28


how come this happen and wasn't before? heating u7700 is no way near it.
 
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Alan.L

Alan.L

Member
R1845 was burnt, C1910 was also burnt.

i replaced R1845, C1910 and u1845. still same problem. not going to s0 state

PP5V_S0 is at 0.14v - 0.20v
SMC bypass show PP5V_S0 is at 5.111v
 
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Alan.L

Alan.L

Member
duke, was just my original 85w magsafe charger via magsafe2 converter all along. just tested with a magsafe2, it booted perfectly. after i read this. https://www.rossmanngroup.com/boards...24-no-s0-rails

:eek:

not sure why this model doesnt like converter.


jason_microsoldering said:
Voltage on SMC_RESET_L?

Voltage on pin 1 of U1900? Do you have 32khz clock?
Click to expand...


hello Jason.

problem solved i think :). was just my "original" magsafe1 charger all this time.

is it worth replacing some half end burnt caps if they are working and not shorting to GND?
apple dialogistic has passed all the test not sure if i should bother....

just going to run more test.
 
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