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[SOLVED]820-00138 Pbus voltage is low 1.6

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supamodz

supamodz

Member
Hey guys working on this 15 in retina which looks like it was sodomized by another shop. I noticed that pbus voltage was 1.6v at charger phase at u7100, I checked my current sense resistors all seem good with normal readings 5v is at input pins of u7100 ac in is at normal 4v at pin 3 dc in is normal at pin 2. Checked ugate and Lgate with the oscilloscope buck controller is dead no cycling what else am i missing here? Where else can i check also no short to ground i checked for that too also smc_rest_L is 3.3v. is that supposed to be high?
I did replace u7100 same results.
 
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dukefawks

Administrator
Bad ISL or soldering or traces/sense resistors. If ACOK is present then you can just inject 12.6V onto PPBUS and the machine should power on.
 
supamodz

supamodz

Member
dukefawks said:
Bad ISL or soldering or traces/sense resistors. If ACOK is present then you can just inject 12.6V onto PPBUS and the machine should power on.
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Ok Duke mark this one as solved, you were right again current sense was the problem. Tho it it was not the resistor was at fault but the fucking test probe point on one of the traces for R7120 was completely missing ran a jumper and is now back to normal again thanks for the advice again you really know your shit.
 
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