Technique to find Short circuit or over current protection fault on laptop motherboar

[imgaurav86]

Hello everyone,

What technique can be used to find a power related issue on a laptop motherboard. For example a laptop will turn on after pressing the power button but will go to standby after few seconds detecting over current situation. How can we troubleshoot this. Laptop stays on if i unplug the LVDS cable. Laptop shows Display on VGA port, motherboard is "Berlin 10G" (google it)

I have tested the LVDS cable and Screen they are both good. Replaced graphic chip already, problem stays the same.

I tried checking resistance for all major power-supply inductor are normal.

bench power supply shows laptop turns off at 1.2Amps

[khaahk]

Re: Technique to find Short circuit or over current protection fault on laptop mother

How did you test the cable?
Test for voltages, which come up (there should be BL 19V voltage, and 3.3V to panel at least) which do not. If there are fuses, then remove them one at a time to test which rail might be the cause.

[fddizon]

Re: Technique to find Short circuit or over current protection fault on laptop mother

you can check the supply voltage for the panel.
normally when given a load, it triggers the issue.
common culprit is ceramic capacitor

[fddizon]

Re: Technique to find Short circuit or over current protection fault on laptop mother

check gate voltage on second fet. if voltage same with source, check 2 resistors coming from gate to ground and going to source.
also check 2 transistors protection circuit.
also, check resistance of 2nd fet's drain pins to ground if shorted.
if the above are all good then feed 2v 1.5amps from dc bench
in this way, shorted component will get warm or hot(if too much amps injected), if none increase amps gradually while looking for warm components.

hope this helps

[ala_borbe]

Re: Technique to find Short circuit or over current protection fault on laptop mother

also try to find LID switch or sensor, it can be that, i had that problem, few times

[PlusCom]

Re: Technique to find Short circuit or over current protection fault on laptop mother

I suppose your lab power supply is 3A? if yes try one with more power.