Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

[todenkopf]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

Bad PQ102 passing insufficient voltage to the b+ rail?

[mcplslg123]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

Bad PQ102 passing insufficient voltage to the b+ rail?

Nope.

[Sephir0th]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

PR727 partial failed?

[volinakis]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

power management-processor state, let the kids alone.

[mcplslg123]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

PR727 partial failed?

No

[mcplslg123]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

Ok, i share the solution. Problem was with +1.5V_CPU_VDDQ dropping to 0.7V on battery .It was 1.23V with adapter only and hence was somehow working. The voltage drop was 'coz of incoorect biasing of mosfet QC3(Gate voltage was 8V on adapter,4.6V on battery). The gate voltage malfunction was 'coz of bad QC5. So the solution was to replace QC5. After replacing,gate voltage at QC3 was 19V on adapter and 14.5V on battery ,so +1.5V_CPU_VDDQ was always 1.5V on any power source. I got this very same problem and solution was same on ACER LA-7912P mb a few months back.

PS: Both the cases came after repair attempt by another technician who perhaps could'nt find the fault.

[Sephir0th]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

Haha, thanks for the resolution! I took the hint with the CPU requirements too closely and focused directly on the VRM controller. So we end up with a voltage behind one of the load switches. Of course you would have looked in vain at the coils as you correctly pointed out.
Admittedly, I wouldn't have thought of that so quickly.

[mcplslg123]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

The whole idea of putting this case study here was to make guys aware that mere presence of voltage on all coils is not a guarantee for mb to post. So that need to have patience and dig deeper. Majority of cases can be solved by simply sticking to basics.

[usyusy]

Re: Dell Inspiron 5520 LA-8241P Not working with battery(For freshers only)

interesting one