Dell inspiron 3168 (15299-2) no power

[madura2010]

Dell inspiron 3168 (Board no=15299-2) no power with battery and charger.No charging.

But after removing battery, worked perfectly.

next day again no power.Then check 19v section.section ok.mosfet driving perfectly.

But 3v LDO was not generated.Then i checked the enable signal of the ic.It is perfect according to datasheet.Then i checked the impedence.It is perfect(444).So i replaced the 3v ic.Then worked.

Again next day, same issue.then i decided to disconnect the ldo line by cutting the path.After that LDO generated well.Then again connecting the path leads to cutoff 3v ldo.Impedence of the ldo line is 444.But KBC vdd pin impedence is 70.Should i want to replace KBC.It is nuvoton NPCE985 non programmable ic.There is a issue in the keyboard as well.customer said thatbkeyboard function well.but during power on sessions, keyboard also not working.

My problem is that, why sometimes generating LDO and working perfectly and during the session of no power, after disconnecting KBC power, LDO regenerates and disappear after connecting KBC power.What should i do?Highly appreciated any comment.

[madura2010]

Highly appreciated your assistance.I will replace it after online purchase

[mcplslg123]

Link schematic if its available. What is the name of the 3V PWM ic? ENABLE LDO status?

[madura2010]

dell 3168 schematic .

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[madura2010]

3v ic sys8286brac

[mcplslg123]

Voltage on pin5/11/12/17 of SY8286BRAC
01.When its working
02.When its not working.

[madura2010]

voltages on SY8286BRAC
01.when it is working

pin5=19v
pin11=18.96v
pin12=3.3v
Pin17=3.3v

02.when it is not working.

pin5=19v
pin11=18.96v
pin12=3.3v
Pin17=0v

[mcplslg123]

The requirement of SY8286BRAC is all fullfilled for generating LDO under both the scenario-so something is wrong on 3V LDO line. I'll suggest to cut the track of 3V LDO and inject 3V/5A on consumer side of LDO. What is the current draw on your dc power supply?

[mcplslg123]

Also give resistance to GND measurement of 3V LDO(after cutting the track) on both sides preferably in ohms mode(meter at 200K scale.

[madura2010]

cutting 3v ldo line generates 3v ldo all the time.

injecting 3v 5a in OCP mode does draw only small current less than 0.01amps.no short is displaying.

cutting Ldo line.
impedence of the end close to the 3v ic=444
impedence of the other end=70

thank you for assisting.highly appreciated the assistance.

[mcplslg123]

I always prefer resistance to gnd measurement in ohms mode and not diode mode. Since its not a dead short on LDO line,its advisable to remove the SIO and see if resistance to GND on consumer side of LDO jumps up. You can also inject 3V on pin19 of SIO and see if it becomes hot. Keep the LDO track cut for the time being.

[madura2010]

I have injected 3v to pin 19 of SIO.only around 100ma consuming.No heat at all on SIO.I will check the resistance to ground after removing SIO and inform.Thank you for the precious assistance.Highly appreciated

[mcplslg123]

SIO should'nt consume 100mA on voltage injection at pin19. I beleive its partially shorted.

[madura2010]

Highly appreciated your assistance.I will replace it after online purchase

[mcplslg123]

You should remove the SIO and check resistance on pin19 of SIO again before ordering. We're still not 100% sure that SIO is bad.