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820-3437 water damage, cycling

Y

Yoel Ren

Member
so I have this board which came in, with water damage around u1900, u6100, and everything on the edge, but its just mild, no broken traces or anything, ppbus and pp3v42 is stable, but pp5v, pp3v3, pp3v3_sus, smc_pm_g2_en, is cycling
pp1v05 is shorted,
there's an audible ticking noise when magsafe is conencted, already unplugged fan, but the ticking is still there, around smc area
when I check pch_intruder_L = 1.6v, if i fix everything, will this end in pch problem ?
 
Y

Yoel Ren

Member
sometimes, the orange light will turn green , and sometimes the orange light will fade away slowly, is this smc problem ?
 
2informaticos

2informaticos

Administrator
Staff member
If 3V42 is stable and also U1900 delivers correct RTC voltage, then all PCH's RTC signals should be good.
Try to fix these first, to avoid wasting time with dead PCH at the end...
 
Y

Yoel Ren

Member
by rtc voltage do you mean only ppvrtc_g3h or all the derivative signal ? ppvrtc and pp3v42 is stable.., i have replaced smc, but still same
 
Y

Yoel Ren

Member
Turn out pp3v3_s0 is shorted, I injevt voltage and lp8550 heat up, changed lp8550 and board turned on.. The question is.. I often encounter low value on this pch_intruder_l and pch_intvrmen.., how do i differentiate If its the pch or power rail problem?
 
2informaticos

2informaticos

Administrator
Staff member
I only found bad RTC resistors because of corrosion, or ripped off by some "specialist" (rarelly this).
RTC caps fail sometime; especially in 3208/09 Air boards.

Last two mentioned signals, have lower voltage usually because oh high ohm resistors.
However, must be higher than 2.1V for good high level threshold.
Multimeter input impedance also makes the voltage to drop a bit when test them; especially PCH_INTRUDER_L.
 
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