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Macbook pro a1278/MB: 820-3115-B/ on and off, voltages fluctuating.

G

gabrielnote

Member
Hey guys!

This card turns on and off quickly, the cooler spins and stops and stays like this in a loop.
The first time I turned it on before starting the tests, I took the battery out and just plugged it into the charger, and it turned on and gave video normally.
After I turned it off, the reported symptom started.



The voltage of PP5V_S3 is oscillating along with all the other sources after it, except for the Vcore which is zeroed without any oscillation: L7550, L7510 and L7520.

I don't know if the problem is before PP5V_S3 or after it.
Anyway, I did the steps below:

We have the 12v GH3.
We have the 16V going into the U7000 (Chager)
R7051 and 7052 OK
R7075 ok
Replaced the ISL6259

Thank you very much in advance!
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

"We have the 12v GH3."
Better to know the exact voltage, with charger alone (no battery).
Believe me, 12.3V is not the same as 12.6V; this information helps us.

Do you get stable 3V3_S5/SUS voltages?
Post U7000 basic voltages: pins 1, 2, 3, 9, 12, 13, 14, 15, 17, 19, 20, 27.
What is the exact resistance (ohm scale) between pins 17/18 and 27/28 of U7000?

Test if board turns on in SMC bypass mode.
 
G

gabrielnote

Member
2informaticos said:
First of all, welcome to the forum!

"We have the 12v GH3."
Better to know the exact voltage, with charger alone (no battery).
Believe me, 12.3V is not the same as 12.6V; this information helps us.

Do you get stable 3V3_S5/SUS voltages?
Post U7000 basic voltages: pins 1, 2, 3, 9, 12, 13, 14, 15, 17, 19, 20, 27.
What is the exact resistance (ohm scale) between pins 17/18 and 27/28 of U7000?

Test if board turns on in SMC bypass mode.
Click to expand...


Post U7000 basic voltages: pins
1: 0V
2: 16.3V
3: 3.99V
9: 0.03V
12: 3.42V
13: 3.43V
14: 3.3V
15: 0V
17: 12.6V
19: 5V
20: 4.98V
27: 16.2V

What is the exact resistance (ohm scale) between pins 17/18 and 27/28 of U7000

17/18 = 28 Ohms
27/28 = 19.8 Ohms
 
2informaticos

2informaticos

Administrator
Staff member
"17/18 = 28 Ohms"
You should get 2-3 ohm there; check R7051/52 and their traces.
You've been asked to do some more tests.

BTW, write directly into reply box, instead of clicking Reply button.
I don't see a real reason to quote an entire post, visible few centimeters above...
 
G

gabrielnote

Member
Good morning teacher!

So, I even washed the whole plate because it smelled like WD40, did not solve. I replaced the C7291 filter capacitor from the 5v line, also replaced the primary U7200 PWM and also did not solve. The machine even started yesterday and worked very well, I thought I had solved the problem, but this morning again presented the symptom!

* One thing I noticed when turning on without video, is that your cooler went up to 100% so it turns off on the button, I turned on again and started the symptom of falling PP5V_S3_REG Soon after I heated the SMC and she returned to connect with video and everything right, I think it has to do with the SMC and Seul pulse PM_SLP_S4_L which is responsible for enabling the PP5V_S3_REG

What do you think?
 
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