820-3115 not turning on, doesn't enter S4 state

djdblaster

New member
Okay, this board was nasty around U3890 so I put it in through UC (first bath UC, finally). PPBUS was shorted so I removed Q3880 and short was gone. Other stuff should also be replaced, but that can wait I think.

Always present rails are good. PP3V42 and PPBUS are 3.42V and 12.59V.

Then I proceeded to check other rails, PP5V_S5 and PP3V3_S5 are also good. That's about it for the rails. PP5V_SUS and PP3V3_SUS are not present. They share Q7822, which fails because P5V_3V3_SUS_EN is not present. It is created by U7940. U7940 VCC Pin and SMC_BATLOW_L are present. PM_SLP_SUS_L is not present. It comes from PCH. Checked input signals and found only SMC_ADAPTER_EN present. PM_RSMRST_L is not present.

Traced that back and got to U7930.

Pin 1 RESET ----- 0V
Pin 2 GND ------- 0V
Pin 3 NC --------- 3.3V?
Pin 4 CT --------- 0.08V
Pin 5 SENSE --- 0V
Pin 6 VDD ------- 3.3V

Probably should have just written rail names. Okay, so, I've replaced it with another one, same results.

Q5040:
SMC_BATLOW_L is 3.3V
PM_BATLOW_L is 0V
PP3V3_SUS is 0V

Reading datasheet about it says that Pin 1 Reset RESET remains low (asserted) for the reset period after both SENSE is above VIT and MR is set to a logic high. A pull-up resistor from 10 k? to 1 M? should be used on this pin, and allows the reset pin to attain voltages higher than VDD.

Tell me please I am in a wrong rabbit hole.

I?m using 2 original 60W and 85W chargers.
 
Last edited:

2informaticos

Administrator
Staff member
You're missing 3V3_SUS, don't watse time around U7930.
PM_RSMRST_L requires 3V3_SUS to goes high...

Check S5_PWRGD, PM_DSW_PWRGD, PCH_DSWVRMEN and the 4 RTC signals (page 16).
32KHz should come out from U2600 too.
 

djdblaster

New member
"Check S5_PWRGD, PM_DSW_PWRGD, PCH_DSWVRMEN and the 4 RTC signals (page 16)." -- They are all present around 3-3.3V.

"32KHz should come out from U2600 too" -- I don't have an oscilloscope to catch that, but DMM has apparently options to check frequency, which I haven't figured out how to use, even after googling and trying to use it on another good board. Model is BM829s.

U2600 pin 12 SYSCLK_CLK32K_RTC voltage present is 0.920V. That's 32 kHz pin?
 

2informaticos

Administrator
Staff member
"the 4 RTC signals"
Please confirm each one you tested by separate.
I want to be sure don't miss any, nor confused with other thing...

32KHz output has usually 0.45V DC; that cannot confirm correct oscillation 100%.

"PM_BATLOW_L is 0V"
I forgot that; it should be high too.
Put good flux and heat PCH, to burn crap under.
 
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