Macbook pro 13" Touch Bar 2018 A1989 the logic board sometimes turn on but sometimes does not

ioan.onutu

Member (✔)

Reputation :

Hello guys,

I have a macbook pro A1989 13" from 2018 with some issues, the most annoying issues. Sometimes it turns on and it works fine for just a short time but the time can vary between 5 min and 20 min (suddenly turn off), and in another time the macbook does not want to turn on at all, so there are 2 cases, both of them are unfavorable.

I tried to reset the SMC and PRAM without any succeed, I tried also the install the last updates, but it would not happened because form each time I tried, the macbook was turn off during the updates installation.

So that means it is obvious there is a hardware issue. I started to measure some voltages on the logic board. I saw just 2 voltages on the board:
L7030: 5.05V
L7660: 3.34V

Do you have any idea in which module area should I investigate? Any advice will help me and it will be appreciate.

Thank you in advance.
 

ioan.onutu

Member (✔)

Reputation :

I took out the logic board I connect just the display and one of the type C usb connector to supply it, but the same results. I thought maybe one peripherical is broken, but apparently is not.
 

Admin

Repair Tv & Laptop
Support

Reputation:

I took out the logic board I connect just the display and one of the type C usb connector to supply it, but the same results. I thought maybe one peripherical is broken, but apparently is not.
Use an external screen.
 

ioan.onutu

Member (✔)

Reputation :

ok, I will try it, but if the display should be the problem in that case, why the touch bar does not light on?
 

Admin

Repair Tv & Laptop
Support

Reputation:

ok, I will try it, but if the display should be the problem in that case, why the touch bar does not light on?
Than you need to check the power source for the touch bar :
Can you put those voltage if they are available
PP3V3_G3H_DFR on pin 1 of C5102
PP1V8_DFR pin 1 C5104
PP5V_G3S_DFR_FILT on pin 1 C5101
 

ioan.onutu

Member (✔)

Reputation :

C5102: 3.35
C5104: 0V
C5101: 0.01V

So if the 1V8 voltage are missing, the SMC is not working right?
And what I notice C5104 is not placed on my logic board, but I measured on pad number 1 to see if there are voltage, but is actually 0.00V...
 

Admin

Repair Tv & Laptop
Support

Reputation:

C5102: 3.35
C5104: 0V
C5101: 0.01V

So if the 1V8 voltage are missing, the SMC is not working right?
And what I notice C5104 is not placed on my logic board, but I measured on pad number 1 to see if there are voltage, but is actually 0.00V...
what voltage you get on L7600
 

ioan.onutu

Member (✔)

Reputation :

C5102: 3.35
C5104: 0V
C5101: 0.01V

So if the 1V8 voltage are missing, the SMC is not working right?
And what I notice C5104 is not placed on my logic board, but I measured on pad number 1 to see if there are voltage, but is actually 0.00V...
I think I found the problem, on PMIC IC I measured 3 voltage rails, the measurement of the voltage was performed on the pin 1 of the capacitors C7865 (expected voltage 0.7 V - 1 V, measured 0V), C7872 (expected voltage 1 V, measured 0V) and C7819 (expected voltage 0.9 V, measured 1.6V).
I'm really sure that PMIC IC is internally broken and for repair that it should replace it, problem in that case, I'm pretty sure I will not find a similar IC for replacement.
 

ioan.onutu

Member (✔)

Reputation :

I measured to the GND that line, and is not shorted
It is very strange what is happened because I measured again the voltage on the coil and for a short time I had 5.01V and after 5 min the voltages went down to 0 V.

I think that some component are broken on that circuit, but I really don't know how could I find which is it....
 

Admin

Repair Tv & Laptop
Support

Reputation:

It is very strange what is happened because I measured again the voltage on the coil and for a short time I had 5.01V and after 5 min the voltages went down to 0 V.

I think that some component are broken on that circuit, but I really don't know how could I find which is it....
PP5V_G3S_DFR_FILT on pin 1 C5101
 

ioan.onutu

Member (✔)

Reputation :

So here are two cases:
1. I measured 5.14V
2. I measured 0.01V

The difference between measurements was almost 10 min.
From what I saw here, at some point the 5V is cut from something, some component maybe, or actually the PMIC is broken.
 

ioan.onutu

Member (✔)

Reputation :

DFR_PWR_EN On C5105 PIN 1 Does it come in a short of time or not .
That is the annoying part, it happened randomly, sometimes I measured 5V sometimes 0V.

Right now I am measuring on C5105 0V, but I am having 0V also on C5101.
Always I measured in the same condition.
 

ioan.onutu

Member (✔)

Reputation :

That is the annoying part, it happened randomly, sometimes I measured 5V sometimes 0V.

Right now I am measuring on C5105 0V, but I am having 0V also on C5101.
Always I measured in the same condition.
And now when the voltage on C5101 is 5.14V, I measure on C5105 1.77V.
It is randomly...
 

ioan.onutu

Member (✔)

Reputation :

Hello,

I still investigate the issue, and perform some different tests to see form where the problem cause.

What I noticed during my tests is voltage on R7691 (P5VG3S_EN) measured on pad 1 is 3.37V and in some seconds become 0.07V, for perform a reset I unplugged the USB type C and plugged again to see if will be the same behavior, in the most of the time it happened the same, but there are some few cases when the voltage remains at 3.37V.

P5VG3S_EN is the signal from U7800, so now I am asking you, could be broken the PMIC IC U7800? or what component can provide that behavior to lose the ENABLE which is provided by the U7800, could be the U7800 itself?

Any idea or hint could be helpful and appreciate it.
Thank you in advance.
Have a nice weekend.
 
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