Ideapad 500 LA-C851P not power on.

[lapfix]

Hello friends.

got this motherboard la-c851p not power on.
Amp taken 0.000..NO schematics or brd are avalaible.
I use La-C771p as mention from another thread.

Taken this voltage :
First mosfet =n-channel = D=19V/S=0v/G=0V
Second mosfet =n-channel = S=0v/D2.5V

So i take BQ24780 voltages :
pin 28 = 19V
pin 6 = 2,7V
pin 24 = 6V
pin 5= 0V must be 3V
pin 3 = 0V must be 19V

No short to gnd , i make a little trick to verify, desoldered second mosfet , tested ok, before soldered i take voltage again , without second mosfet so ..

First mosfet =n-channel = D=19V/S=19v/G=25V
ACOK = 3V
CMRSRC = 19V

So my charger ic and mosfets are ok...what i am missing !!!

[mcplslg123]

Re: Ideapad 500 LA-C851P not power on.

Very likely a shorted discharge mosfet. Check voltage on charging coil. Is it showing 19V?

[lapfix]

Re: Ideapad 500 LA-C851P not power on.

Very likely a shorted discharge mosfet. Check voltage on charging coil. Is it showing 19V?

Thank you mcplslg123

No , i find 2,6V a pl301..Same volt at sensor resister and drain of second mosfet.

i test the 3 mosfet of battery charge pq302/305/306 out of board and they are ok .

What to check else !!

[Mayank tater]

Re: Ideapad 500 LA-C851P not power on.

If after remove second mosfet you get 25v on 1st mosfet get so change 2nd mosfet its solved

[lapfix]

Re: Ideapad 500 LA-C851P not power on.

If after remove second mosfet you get 25v on 1st mosfet get so change 2nd mosfet its solved

Thank you maynak , second mosfet was tested out of barder and his is at good condition , but try your advice and still same issue.
When i remove second mosfet and inject 20v at Drain place i got 0,O10 amp consumption, try to power on with button it reach 0,048 amp than back to 0,010 amp.

[mcplslg123]

Re: Ideapad 500 LA-C851P not power on.

Replace the charger IC even if everything is ok after removing 2nd mosfet. make sure to check suffix as BQ24780 and 24780S are not compatible. If condition remains unchanged, try a jumper to cmsrc pin of bq24780 and the other end to Drain of 1st mosfet(This will bypass the current sensing). Update about result. Sometimes replacing the caps connected to dc-in fets solve this mystry(specially on acer). BQ24780 often has this problem and there is no perfect one solution. the solution varies from board to board.

PS: I assume you have checked and confirm there is no shorting after the 1st dc-in fet.

[lapfix]

Re: Ideapad 500 LA-C851P not power on.

I assume you have checked and confirm there is no shorting after the 1st dc-in fet.....Yes of course , no shorting at all coil , tested as usuall twice with diode mode and ohm mode .
Update : before do what you ask for..inject 3V at PL402 : 3valws i find a big consumption 0.900 amp ,whith help of flirone i got a hot place at UA1 ,lan circuit i desoldered still got consumption of 0,130 amp , i find U13: the 3 and 5VS getting hot too , desoldered still got consumption....than i desoldered PU401 : the 3 valws...the charger circuit with his 2 mosfets works good and i find 19V at sensr resistor!

I try to test 3VL for short or remplace the SYX196BQNC circuit .
In other thread you don t recommand SY8208BQNC and another friend post that SY8206BQNC is ok...So i will try and give feedback

[mcplslg123]

Re: Ideapad 500 LA-C851P not power on.

Good progress friend. however, you should've checked shorting at 3V earlier before troubleshooting charger IC.