ACER 515-56G (LA-K092P) Not Power

[tipoti]

Hello,

There is no voltage on pin4 of the PQB3 mosfet. When I skip 1-2-3 with pin5, the device turns on. Of course it's not charging.
pqb3 and pqb4 don't have any shorts

can you help me thanks

[mon2]

Re: ACER 515-56G (LA-K092P) Not Power

Remove the series resistor on the gate pin. Do not lose it.

Power up again. Measure the voltage to ground of the same series resistor but at the charger IC pin.

What is the voltage?

[tipoti]

Re: ACER 515-56G (LA-K092P) Not Power

There is no voltage on pin1-2 of the PRB4 resistor, the resistor is OK

[mon2]

Re: ACER 515-56G (LA-K092P) Not Power

Remove PRB7 which is the ACDRV series resistor.

Then check again the ACDRV voltage to ground on the charger IC. It should be ~25v if the charger IC is trying to enable the 2*DCin mosfets.

[GREAT_MERA]

Hello,

There is no voltage on pin4 of the PQB3 mosfet. When I skip 1-2-3 with pin5, the device turns on. Of course it's not charging.
pqb3 and pqb4 don't have any shorts

can you help me thanks

any solutions?

[mon2]

Sure. Post your details. The op of this thread went into the witness protection program.

Review the charger bible by piernov - see the sticky above. The root cause is often within the first 2 DCin mosfets. To confirm, test their resistance (without power):

source / drain
source / gate
gate / drain

Post each measurement. Not 'they are not shorted' comments. Only the true measurements will help to diagnose the fault.

[GREAT_MERA]

Sure. Post your details. The op of this thread went into the witness protection program.

Review the charger bible by piernov - see the sticky above. The root cause is often within the first 2 DCin mosfets. To confirm, test their resistance (without power):

source / drain
source / gate
gate / drain

Post each measurement. Not 'they are not shorted' comments. Only the true measurements will help to diagnose the fault.

voltage on prb7 input without it, is 0v

here are the first two mosfet measurements.

pqb3
s/d=7.9kohms
s/g=233kohms
g/d=120mohms

pqb4
s/d=8.33kohms
s/g=240kohms
g/d=120mohms

[mon2]

They both look to be in trouble. Each measurement should be hundreds of kohms or higher.

With no power to the board, measure the resistance to ground of the drain pins (5-6-7-8) of the 2nd dcin mosfet. We are testing if the main power rail is shorted or not which may have caused these 2 DCin mosfets to fail. If the resistance is ok, suggest to remove the 2nd DCin mosfet first and measure the mosfet while it is out of circuit. Most likely, the part is defective and very possible that the first mosfet should also be replaced. The mosfets are very common across motherboards so you should be ok to use a donor board.

Share details of the next measurements and also the mosfet you may use for the replacement(s).