820-4924 - Green/orange ok, no power.

[gcain]

Customer said he messed the tiniest but of liquid on the keyboard and next morning it wouldn't turn on. Board is one of the cleanest I've seen. Absolutely no trace of any liquid anywhere. It isn't even dusty.


PPBus = 12.59v
PP3v42_G3H = 3.42v
PP3v3_s5 = 3.33v
PP3v3_s4 = 1.9mV
PP5v_S5 = 5.02v
PP5v_S4 = 0v.

 

[gcain]

PP3v3_S4 spikes to 2+v for a moment two or three times when I first connect power.

 

[dukefawks]

So it is power cycling. There must be corrosion for sure. Inspect closer as it could be pretty much anything. Vcore power cycling too?

 

[gcain]

I have been over this board several times now and can't see any corrosion, it's spotless. :'(

PPVCC_S0_CPU seems to be cycling too, my DMM picks up a spike every 10 seconds or so. Guessing it's missing ones in between.

Is there anyway to isolate which side the issue is occurring on?

 

[dukefawks]

U6100 area and resistors, J6100, U1950 closely inspected? If Vcore comes on all other power rails will be ok.

 

[gcain]

I still have this board in my desk and can't find anything to cause the cycling.

Any further suggestions?
Could it be a corrupt bios similar to the Air from yesterdays post?

 

[dukefawks]

Could be BIOS but unlikely as it was a liquid spill. Swap another chip on there or flash it. Make sure to keep a backup of the original.

 

[gcain]

Swapped the bios, but same behaviour.

 

[dukefawks]

Check U1950 and possible crap under SMC.