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820-00875 missing PP5V_S4

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cwalex

New member
Hi,

I have a board here that won't power on after a liquid spill. U7650 and Q7660 were badly corroded so I have replaced them. After cleaning the board in the ultrasonic cleaner, the rest of the board looks OK. It's missing PP5V_S4. I'm testing using an original Apple 87W USB type C charger and cable from Apple. Here are the readings I have so far:

PPBUS_G3H = 13V
PP5V_S5 = 5V
PP3V3_S5 = 3.3V
PP5V_S4 = 0V 31K to gnd on that line

SMC_PM_G2_EN = 3.4V
PM_SLP_S4_L = 0V
ALL_SYS_PWRGD = 0V

Any and all advice welcome :)

Cheers,

Alex
 
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dukefawks

Administrator
Well yeah, this could be absolutely everything. Must be corrosion somewhere else but you have cleaned it already :(

U1900 area checked? 32KHz on pin 10? PP3V1_RTC present?
 
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dukefawks

Administrator
Pictures are of no use, no detail or resolution.

Is there any power cycling on PP5V_S4? Check with scope as multimeter may be too slow to catch it.
 
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cwalex

New member
Hi Duke, it sprung to life while I was probing it with the CRO probe... PP5V_S4 and all the other rails are now present. I'm sure the problem is related to U7650 but visually it looks fine. I'm going to reflow it with some flux and a bit of solder just incase. I really don't like situations like this where it's not totally clear what the problem and solution was. Thanks a lot for your help :)
 
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