820-4924 green/orange ok, no fan spin

Dozer

Member
hi everyone.

i got that board from customer. he said liquid spill.

i have 12.54V so smc is working

PP3V3_S5 is 3.3V

PP5V_S5 is 5.0V

PP5V_S3 is 0V

PM_SLP_S4_L I get spices of 3.43V every about 3sec.

I found corrosion aroud U8330 but i think thats is not important now

next spot is around U 1900, but PPVRTC_G3_OUT is nice 3.42V and
PCH_CLK32K_RTCX! is a nice signal ,

that should be so because i have spikes on PM_SLP_S4_L, means the RTC is working

around u8005 is not like it should look.

i measured y1915, the 24Mhz signal is coming but frequently like the spikes from PM_SLP_S4


where to start here for the best?
 

Dozer

Member
thanks for help.

PP5v_S4 is 4.95V pulsing as well

5v_S3 is not pulsing, 0V

Reesistance to ground is about 12kohm
in diode mode is 0.390, another same board has here .402
 

SMMRepair

Member
Fan does not spin on this model when it powers on, just fyi.

Definitely clean up the area you mentioned was 'ugly', then check for shorts across all rails (probably s3/s0 in this case) if you do in fact have a pulsing rail(s).
 

SMMRepair

Member
I don't like to clean boards before repairing them, but you can if you want. If the liquid damage is spot/minor, then I don't clean. If you see liquid across the board or in 4-5 spots, then cleaning it won't hurt. I repair, then clean last.
 

dukefawks

Administrator
It is power cycling. Could be anything at this point. Clean up the visible crap and replace U1900 if there was corrosion there. Crap under SMC is also likely.
 

Dozer

Member
cleaned in ultrasonic and replaced u1900, there was crap under it and 2 traces coroded Pin 13 and Pin 1
so i repaired that and now i get pulsing PP5V_S3 and pulsing PP5V_S0 but no PP3V3_S0
I measured in diode mode pp3v3_so to gnd and get a short. so i will look for that (injecting that voltage in that rail and report back.

the smc is near u1900 but it looks not bad around it.

EDIT: there is no short in PP3V3_S0, i just a measure error.
No short in PP3V§_S0 but no voltage and no pulsing here.
 
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Dozer

Member
PP3V3_S0_FET is pulsing 3.3V

PM_PWRBTN_L is 3-41V stable
SMC_RESET_L is 3.36V stable

PCH_CLK24M_XTALOUT is nice 24Mhz but pulsing
 
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Dozer

Member
checked u1950, no corrosion to see. to be shure i gave it a nice reflow

pin 1-3, pin 5-7 are pulsing

reballing smc, here no crap to see as well

after reflow u1950 and reballing the smc there is no change. problem is still the same. :-(
 

Dozer

Member
C1031 Pin 1 I get only 0.7Ohm to gnd, on a good board i have 27Ohm, seems to be shorted.

is it a good idea to incect here 1.8V and look with the thermo cam? i am not sure about the voltage value?
 

dukefawks

Administrator
yeah 0.7Ohm on CPU Vcore is a fried CPU. Forget about injecting voltage as the CPU will always heat up, even a good one will get warm as the resistance is low enough for that.
 
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