820-00840-A not starting

Fanfwe

Member
Hi, I have this 820-00840-A board with liquid damage around U7650 and the backlight stuff also.
I've narrowed it down to U7650 not creating PP5V_S5 and that's due to PMIC_EN_P3V3S5 missing.

So, checking around PMIC, I could see that PP3V1_RTC is good, PP3V3_LDO3V is good, PP1V25_VREF is good.
PMIC_SHUTDOWN_L is high.
On this board, R7828 is the one present.

What should I check next ?
 

Fanfwe

Member
PPBUS is 13.02V
And yeah I should maybe have started there, but no issue with the CD3215 stuff, of course. 20V from charger, which also implies 3v3_g3h is indeed present.
 

Fanfwe

Member
Diode mode and resistance to ground:
L7670: 0.407V 900Ohms
L7690: 0.353V 780Ohms

PPVCCGT: 0.0023V 4.6Ohms
PPVCCCPU: 0.0043V 9Ohms
PPVCCSA: 0.0066V 13.37Ohms
PPVCCPCH: 0.0652V 130Ohms
PPVCCIO: 0.0531V 106Ohms
 

Fanfwe

Member
Diode mode at 5V_S5 is 0.410V, so there's no short.
Traces, solders and probe points look okay, and I have tested continuity for the few ones I had a small doubt, they are all good.
I guess I'll try to replace the chip, just in case as you said, but I can't see how it can be the issue when the enable signal is low (and not shorted to ground)
 

Fanfwe

Member
Yeah that's what I thought too. I don't have any right now. I'll put this aside for now and report back later once I get some and replaced it.
Thanks
 
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