Macbook pro A1278 green light but no power

[dycc]

Re: Macbook pro A1278 green light but no power

mean all these lines are shorted if it is ohm.

[robertpritchard]

Re: Macbook pro A1278 green light but no power

guess thats bad,, is there a chip that could be bad

[robertpritchard]

Re: Macbook pro A1278 green light but no power

i have no volt at L7260 or L7220 either

[dycc]

Re: Macbook pro A1278 green light but no power

guess thats bad,, is there a chip that could be bad

very bad and also lot of job. do you have a variable power supply??

[robertpritchard]

Re: Macbook pro A1278 green light but no power

no i dont but i can pic one up today

[dycc]

Re: Macbook pro A1278 green light but no power

normally for each line shorted you need to find all IC (on that line) , remove them one by one till find the one (IC) , who bring short to the line
.

[robertpritchard]

Re: Macbook pro A1278 green light but no power

ok and ill try to pic up a sd card for my microscope so i can take a pic of U7200 for you it looks bad and so does everything around it.. this logic board was shutting off and on when i got it but was running had water damage around the U7200 so i ultrasonic cleaned it .. yes i have a good one and i have cleaned lots of boards but this is the first one that was running before i cleaned it and now its not

[dycc]

Re: Macbook pro A1278 green light but no power

with power supply you need to set voltage at 2.5v 2A apply to the 5V and 3V lines shorted until the bad components start heating

[robertpritchard]

Re: Macbook pro A1278 green light but no power

ok thanks

[dycc]

Re: Macbook pro A1278 green light but no power

ok and ill try to pic up a sd card for my microscope so i can take a pic of U7200 for you it looks bad and so does everything around it.. this logic board was shutting off and on when i got it but was running had water damage around the U7200 so i ultrasonic cleaned it .. yes i have a good one and i have cleaned lots of boards but this is the first one that was running before i cleaned it and now its not

ok

[dellxps15]

Re: Macbook pro A1278 green light but no power

to start macbook needs 12.5 volt, 3.42 volt and 3.3 volts.

check if these voltages are presents

[robertpritchard]

Re: Macbook pro A1278 green light but no power

Thanks i have no 3.3 volt rail

[dellxps15]

Re: Macbook pro A1278 green light but no power

3.3 volt rail is supplied by u7200 that u say is bad, so
1st make a picture of it
2nd measure "vin" and "en" point reading the schematic

[robertpritchard]

Re: Macbook pro A1278 green light but no power

en pin 13 is 3.02
vin pin 16 ... the numbers dont stop jumping around

sorry my phone dosent take a good enough pic ..

[dellxps15]

Re: Macbook pro A1278 green light but no power

"the numbers dont stop jumping around " what do u mean ?

pin 16 must have 12.5 volt

if no pin 16 voltage, not stable 12.5 voltage, no 3.3 volts on L7220 replace u7200

[robertpritchard]

Re: Macbook pro A1278 green light but no power

had to wait for the chip to arrive changed it and it works great thanks very much merry christmas

[dellxps15]

Re: Macbook pro A1278 green light but no power

had to wait for the chip to arrive changed it and it works great thanks very much merry christmas

wich chip? almost forgot about this repair u7200 ?

[audiomodder]

Re: Macbook pro A1278 green light but no power

check boardview

dycc, it's so very nice of you to help with this. I have the same symptom and will follow your instructions carefully to see if I can locate the issue.
Thank you!!

[audiomodder]

Re: Macbook pro A1278 green light but no power

Symptom: Green charge light, turns amber to charge battery, stays green when no battery. No power up.
OK I made some measurements:

SMC_RESET_L: 3.43v
SMC_PM_G2_EN: 3.47V
S5_pwrgd: 3.3v

diode checks (red on ground)

PPBUS_G3H .438 = 12.57V
PP3V3_S5 .362 = 3.3V
PP5V_S5 .484 = 5V
PP5V_SUS .376 =5V
PP3V3_SUS .297 = 3.3V
PP3V3_S4 .352 = 0.5V

OK so I'm looking into that last one. Looks like my model is the K90i MLB variant.
PP3V3_S4 is controlled by Q7800 and Q7802 FETs - those both check out.
BUT Q7802 gate is being held low, making it inactive. The signal that controls that is P3V3_S4_EN

P3V3_S4_EN is controlled by PM_SLP_S5_L. This is low but it needs to be high for the system to run. That signal is controlled by the giant U1800 Cougar Point CPU.

Anyone have any ideas on where to go from here?

[audiomodder]

Re: Macbook pro A1278 green light but no power

ah looks like PM_SLP_S3_L, PM_SLP_S4_L, and PM_SLP_S5_L are all low. So I really suspect Intel Cougar U1800 is not working right.

I got low on PM_PCH_PWRGD, and also on SML_PCH_0_CLK

also I hear a faint clicking sound and green light only happens 1 out of 3 times...tried 2 different chargers and same thing. It seems like the green light is finicky :/

any help greatly appreciated!