It's clear now. My thanks to you and to Segan.
Feed back :
Ok added missing R1242 to circuit, got EN1 and EN2=2V, so the +V5AL supply to R1242 collapses in 2V. Suspected TPS51120 and desoldered it.
Before it's replacement, I connected adapter in order to identify the malfunction of Q1031, which I previously shunted.
At this stage, a tragic problem happened, a smoke came from U1007 Lan Controller, also, +V3_LAN and +V3A rail were shorted to gnd ? a phenomenon that I couldn't undertand as no voltages should exist, when TP51120 is removed, except the +VBATP, do you agree ?
Also found resistance of +V5A to gnd very small : 29 Ohms ?
Removed smoked U1007, and traced thoroughly +V3A line : found and removed shorted Q27, U1021 and U1017 but +V3A SHORT is not yet gone ?
1*-So, what probably happened to kill simultaneously Lan Controller, Q27, U1021 and U1017 though TPS51120 was removed ?
2*- What else to check to solve short issue on +V3A rail ? Already supplied rail with +3VDC power supply, didn't find any component which heats !
3*- How to solve +V5A line "29 Ohms resistance" to gnd ?
Unfortunately lot of steps back in this repair, as a result of this tragic problem!
Thank you for giving good steps to solve these issues .
Отредактировано mohkamtun (21.04.2015 01:58:32)