Macbook Pro A1398 - 820-3332A. No Fan Spin.

arshees

Member
Macbook Pro A1398 - 820-3332A. Fan spins continuously on battery but no chime and no display. No fan spin without battery, Yellow light on Magsafe Adapter. Checked all voltage rails and results as below.

PPBUS_G3H = 12.6v
PPVIN_S5_HS_COMPUTING_ISNS = 12.6v
PPVIN_S5_HS_GPU_ISNS = 12.6v
PPVIN_S5_HS_OTHER_ISNS = 12.6v
PP18V5_DCIN_CONN = 16.3v
PP3V42_G3H = 3.4v
PP5V_S5 = 5.1 v
PP3V3_S4 = Missing.

What next?
 

2informaticos

Administrator
Staff member
This board will not start without 85W charger, if battery not present.
Board turns on with both charger and battery connected?
Do you get USB activity?

Start resoldering U8900 with leaded solder.
 

arshees

Member
Yes. board turns on with both charger and battery connected and after connecting to 85w charger, turns on without battery. USB activity - just the red light on. no blinking. Fan spins but no display.
 

2informaticos

Administrator
Staff member
You should get voltage on L8930/60.
L7550/60 only get voltage under heavy graphics load, when Intel graphics is used.

Check GPU Rail Sequencing, page 88.
 

arshees

Member
Checked rails and result... I hope i am doing it right. All rails showing 3.3v doesn't seem right....
P3V3GPU_EN - R9121 Pin 1 - 3,3v
P1V8GPU_EN - R9122 Pin 1 - 3.3v
GPUVCORE_EN - R9123 Pin 1 - 3.3v
P1V35GPUFB_EN - R9124 Pin 1 - 3.3v
P1V05_S0GPU_EN - R9125 Pin 1 - 3.3v
 

2informaticos

Administrator
Staff member
You measured enable signals.
Check if each power supply which receive the enable, generates output voltage...
 

2informaticos

Administrator
Staff member
P3V3GPU_EN controls 3V3_GPU and so on.
Follow each enable signal and see if corresponding power supply (just a MOSFET in some case), generates the output voltage.
P3V3GPU_EN --> Q7872 --> Q7870 --> 3V3_GPU...
 

arshees

Member
Just a quick observation. I was checking GPU voltages and found PPVCORE_S0_GFX_REG - 900mv on Pin 1 of C8961/63. I was wondering if this is the cause of the problem. Should I change U8900 and check? Just a thought before I post the voltages you asked for later today.
 

arshees

Member
Findings as requested. Hope i am on the right track...


P3V3GPU_EN - PP3V3_S0GPU – Q7870 Pin 2 – 3.3v
P3V3GPU_EN_L – Q7872 Pin 3 – 300mv
GPUVCORE_PGOOD – U8900 Pin 1 – 3.1v
GPUFB_PGOOD - U8350 Pin 14 – 1.7v
P1V05_S0GPU_PGOOD – U8310 Pin 9 – 1.8v
 

2informaticos

Administrator
Staff member
Seems that you didn't understand me.
I said
"P3V3GPU_EN --> Q7872 --> Q7870 --> 3V3_GPU"
in other words, if 3V3GPU_EN is present, then 3V3_GPU must be present too.
I was expecting that you apply the same rule for the other GPU rails...
 

arshees

Member
Sorry.. I simply can’t get the hang of this one. Any links where I can read up on this. I feel I should give up on this board.
 
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