820-4924-A water damaged, doesn't turn on

[djdblaster]

Board was water damaged. Fixed a couple of parts to get ISL working. The rest I have cleaned with iso.

PPBUS_G3H -------------------------------- 12.56V
PP3V42 --------------------------------------- 3.42V
PP5V_S5 ------------------------------------- 5V
PP3V3_S5 ----------------------------------- 3.3V
PPVRTC_G3H ------------------------------ 3.3V
SMC_CLK32K ------------------------------ 1.7V
PCH_CLK32K_RTCX1 ------------------- 0.42V
PM_CLK32K_SUSCLK_R --------------- 1.7V
SMC_ADAPTER_EN ---------------------- 3.3V
PM_BATLOW_L ---------------------------- 3.3V
PM_SLP_SUS_L --------------------------- 3.3V
PM_PWRBTN_L ---------------------------- 3.42V

I'm using a genuine 60W charger. I could try another one I guess.

S4 rails are not present. Am I missing something?

 

[2informaticos]

Post 3V3_S5. 3V3_SUS, PM_RSMRST_L.
Trigger SMC_ONOFF_L and check if PM_PWRBTN_L reacts.
No pulse at least at PM_SLP_S4_L?

 

[JohnB8812]

Yes check all that 2informaticos suggested. Also, check resistance between pins 17/18 and 27/28 of the ISL6259 you said there was liquid there

 

[djdblaster]

PP3V3_S5 ---------- 3.3V
PP3V3_SUS ------- 3.3V
PM_RSMRST_L -- 3.3V

I haven't triggered SMC_ONOFF only because I've found R7202 broken, along with its trace. (Even though I don't see how that would make prior stuff not work)

There is no pulse at PM_SLP_S4_L.

JohnB8812 PPBUS_G3H is 12.56V. I've rebuilt the circuit around ISL. They all measure correct. including pins 17/18 and 27/28 Sorry I haven't written that explicitly what has been done.

 

[2informaticos]

"I haven't triggered SMC_ONOFF"
Try and comment.
Check PM_SLP_S4_L reaction at the same moment when SMC_ONOFF_L is triggered...

 

[JohnB8812]

If you're 100% sure pins 17/18 and 27/28 measure 20.9 and 3.9 approximately, then yes next thing to try is SMC_ONOFF_L and check if PM_SLP does anything.

 

[djdblaster]

Got it to work. PM_SLP_S4_L is back due to R7202 being corroded and messed up all necessary rails prior to PM_SLP_S4_L.

Mark as solved please.

 

[2informaticos]

R7202 is not involved in PM_SLP_S4_L generation.
In fact this signal should appear in the first moments of power sequence.
I bet it was pulsing and not maintained because of missing power good from VCORE power supply.

Be aware of wrong assumptions, is not the best way to learn...

 

[djdblaster]

I tried to catch some pulse on PM_SLP_S4_L as soon as the charger was connected, but didn't see anything. I tried 3 times.

As for R7202, that is correct. It is not related in PM_SLP_S4_L generation, rather as input voltage for U7200 which releases CPUVR_PGOOD, which goes to U1950, creates PM_S0_PGOOD, responsible for creating SYS_PWROK_R, after R1962 it is PM_PCH_SYS_PWROK, and finally comes to CPU, which then releases PM_SLP_S4_L.

Well, either my eyes are not seeing good or something, but you say that even without U7200, there should be a pulse on PM_SLP_S4_L from CPU?

 

[2informaticos]

CPU cannot get VCORE if PM_SLP_S4_L is not released first by PCH...
You may not see that signal pulsing when charger is connected.
But you can see that if manually trigger SMC_ONOFF_L signal.
Better to use an o-scope to catch fast pulses...

PM_SLP_S4_L is used to enable S3 voltages.
PM_SLP_S3_L is used to enable S0 volatges.