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[SOLVED]820-3476 (s0 rails present but not turning on anymore)

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ytesfay80

ytesfay80

Member
This board sent in because the fans were running on full blast after a water spill. I ran the efi diagnostics and it told me the trackpad cable was the issue so I replaced that and the machine was working fine a couple hours ago. I decided to clean the corrosion from the liquid damage which was only around the following areas.
Q8150/Q1930 (attached image)
R8158/59
Q7310 (very light and only on pin 1 side)

I just put some flux and heated the area to remove corrosion. I replaced R8152&R8158 because they looked burned on one side. After doing those repairs the board no longer turns on even though PP5V_S0 and PP3V3_S0 are present.

I measured R8167 and on Pin 1(PM_SLP_S3_BUF_L) there was 3.32v and Pin 2(ALL_SYS_PWRGD) there was 0.11v. I replaced Q8150 and U1930 since they were connected to ALL_SYS_PWRGD but that didn't change anything.


Update: I see a little corrosion on the C1924 side of the U1900 clock chip and C1924 looks slightly black on one side. Could that be causing this and should I go ahead and replace this?

Also I see U5110 has some corrosion on pin 1 but 3.4v was present on all pins except for pin 2. Pin 4 (SMC_MANUAL_RST_L) - 2.78v
 

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2informaticos

2informaticos

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Staff member
There are many S0 voltages, not only 3/5V; and all required to keep high ALL_SYS_PWRGD.
So check which voltage is missing and fix that.
 
ytesfay80

ytesfay80

Member
PP1v05_s0 and PP1v5_s0 were both present. PPVCC_S0_CPU was measuring only 0.05v.

I replaced U1900 and C1924 but that didn't change anything. Is SMC_MANUAL_RESET_L being 2.78v an issue?

All of these measurements are without the keyboard, trackpad, or other external components plugged into the board.
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
Leave the CPU core voltage now.
Look at the voltages involved to generate ALL_SYS_PWRGD.
That signal is required in order to enable CPU core voltage.
 
ytesfay80

ytesfay80

Member
Okay I was measuring Q8150 and I was getting 0v on Pin 5. I traced it back to R8151 and found that its resistance was very high.
I replaced R8151 and now ALL_SYS_PWRGD is 0.29v instead of 0.11v. Pin 5 of Q8150 is now 1.03v.
 
ytesfay80

ytesfay80

Member
Okay so I replaced R8151 and R8156 after measuring their resistance and now the fan is back spinning and vcore is present.

Crazy how a couple of resistors can stop a machine from turning on.

Thanks. You can mark this as solved.
 
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