Laptop model :-Dell 3542
PCB Number :- Cedar_Intel 13269-1
Customer complain :- Suddenly misbehaved
Problem :- Power on but restart continuously
Observation:- If we remove RAM it will stable ( no restart) , if we plugged RAM it will restart continuously
Solution :- First try physical observation,
because of rainy season most of the problem present due to moisture and oxidation , board was neat and clean no moisture no oxidation persist , after that check supply status almost all supply was stable, vcore is also stable then try to check data on Lpc bus , data is available now got an idea that CPU is in working condition but any one of s0- state requirements not full filled , first start with back tracing of s0-state supply's ,almost all supply's ware stable but 1D5V_S0 was misbehaved not stable, continuously (up - down) at pin no.5 of PU5101, try to check Impedance across to ground was matched to working board , so try to check input requirements of PU5101 was also full filled & stable, now PU5101 was suspected ,, but start with linear components so first remove PC5120
Bingo PU5101 output is stable now ,
The board turned on perfectly with RAM ,
Job done
