820-4924 orange light not turning on

wgaca

New member
A bit of history before we start

Liquid damage around the SMC and a few other areas. After repairing all the visible damage and traces it was still not turning on. I decided to replace the SMC and it turned out it had quite a bit of corrosion underneath, however, didn't turn on after the new SMC. I left it for the day after and when i tested again it turned on (booted OS just fine). I cleaned the board in ultrasonic and it stopped working again after that. (missing pm_slp_s5_l)

I took a working board with a faulty CPU and started taking known good parts to replace. All of the following i replaced are known good working parts.
SMC - Didn't work
U7100 - Didn't work
U5110 - Didn't work
U1900 - Worked

So, I said to myself, perfect, it was the clock. I cleaned the board and boom doesn't work again.
All the measurements are taken after this point.

PPBUS_G3H - 12.47V
PPVRTC_G3H - 3.31V
EDITED: PM_SLP_S5_L - 1.49V
PM_SLP_SUS_L - 0V

S5_PWR_EN - 3.3V
CHGR_A/BMON - 0.03V/0.07V
SMC_BC_ACOK - 3.1V
PP5V_S5 - 4.98V
PP3V3_S5 - 3.31V
PP3V42_G3H - 3.41V
PP3V3_S5_SMC_VDDA - 3.41V
PP3V3_S5_AVREF_SMC - 3.27V
SMC_PBUS_VSENSE - 0V


There was no damage around u7100 nor around u1900. The damage was heavy in and around the SMC (all fixed) and U8330 (fixed as well)

TLDR:
The board didn't work after fixing all the visible damage but turned on fine after 12 hours of sitting.
It stopped working again after cleaning and started working after replacing the clock chip.
It stopped working again after cleaning and I have no clue why. I cleaned 3 other boards today without any issues.

It might be worth mentioning that both pins 67 and 68 under the SMC were completely gone due to corrosion but both are saying not connected.
Using OEM 85W charger for all tests.
 
Last edited:

2informaticos

Administrator
Staff member
U1900 is not only clock chip.
It also generates RTC voltage for PCH.
Check the 4 PCH's RTC signals.
Also check PCH_DSWVRMEN, PM_BATLOW_L and PM_DSW_PWRGD.
 

wgaca

New member
PM_BATLOW_L - 1V
PCH_DSWVRMEN - 2.45V
PM_DSW_PWRGD - 3.45V

PCH_INTRUDER_L - 1.67V
PCH_INTVRMEN - 2.5V
PCH_SRTCRST_L - 3.25V
RTC_RESET_L - 3.24V
 

2informaticos

Administrator
Staff member
"PCH_INTRUDER_L - 1.67V"
Good enough to explain your symptom.

Check R1301; force 330K instead of 1M.
If still low, heat PCH area with quality flux.
 

wgaca

New member
R1301 measures 800+K
Now it turns on of course when I left it overnight.

Should I heat the PCH with some flux or leave it as is and test how it's going to go?
Any recommendation in this case how to make it reliable?

PCH_Intruder_L - 1.66V and it still turns on

Edit: It might be worth mentioning that R5310 and R5311 had some corrosion but didn't look like anything went underneath the PCH. I guess it is a possibility in this case.
 

wgaca

New member
Here are the steps I took to check if that is the issue:

1 - Heated the PCH with some flux, the device turned ON. I ultrasonic cleaned and it didn't turn on again.
2 - I replaced R1301 with 330K resistor. It turned ON. I wanted to make sure if that will fix the issue so I ultrasonic cleaned again. Didn't turn on.

PCH_INTRUDER_L - 2.5V

I will leave it to rest till tomorrow and I guess it will work again.
Any other ideas?
 

2informaticos

Administrator
Staff member
2.5V is good enough.

If turns on after heating PCH, should be internal PCH issue.
Still possible broken solder/trace underneath.

"PM_BATLOW_L - 1V"
Ooops, I forgot this.
Must be high, or PCH doesn't start power on sequence.
 

wgaca

New member
Ok i checked today it didn't turn on after leaving it for some time.
PM_BATLOW_L - 3.3V

I heated the PCH from below and it works. I guess that will be crap under the CPU. I will keep it as a test board as I don't think it's a reliable fix
Thanks for the help
 
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