Acer A515-51 - C5V01 LA-E891P Rev 1c

[coffeebreath]

laptop lights wont turn on, wont power on. When plugged in I get 0.4v-0.8v directly from the DC jack plug on the motherboard. 19v from the charger.

Thank you.

[mon2]

Measure the voltage to ground on each side of the DCin power jack EMI coil(s) @ PL101 / PL102. Post each measurement. You should see 19v pass through.

[coffeebreath]

PL101: 0.4 -0.8v. All my power adapters keep tripping I think. Light blinks

PL102 doesn't exist. Doesn't look like it's ever existed

[mon2]

Remove all power / no battery.

Meter in resistance mode. Measure the resistance to ground of PL101 - check both sides of this coil. What is the resistance? You can use a metal shield on the board for ground.

[coffeebreath]

PL101 - 13.87

[mon2]

Need the units of measure from your meter. Is it ohms? kohms? Mohms? Share a pic of the meter face if available when you are testing this resistance.

[coffeebreath]

20k

[mon2]

So the measurement is 13k88 = 13,880 ohms. No short here.

Noting this, if your power adapter is not defective and the DCin power connector also not defective, you should have the power adapter voltage available on each side of this EMI filter.

Confirm the power adapter is ok when it is not mated with the board. Suspect now is that your DCin power connector may be defective.

[coffeebreath]

The DC jack is connected via removable cable. I remove the cable and test it and I get 19v from the motherboard connector. The cable seems fine.
I have tested it with multiple chargers now.

[coffeebreath]

[mon2]

Ok. Locate the 2 x DCin mosfets. Still with no power -> measure the resistance to ground of each of PQ303 (5-6-7-8 = Drain pins). What is the measurement in ohms? This is the main power rail for the logic board.

Your issue is when you mate a working power adapter to this logic board so someone in the power path is shorted and causing the adapter voltage to tank.

The next step is to check the resistance across both of these mosfets as follows:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. If your meter reports 'OL' = over limit, then switch to a higher resistance scale till you have a reading. Checking for a low resistance = defective mosfet.

[coffeebreath]

source (1-2-3) & drain (5-6-7-8) - 20k - 13.27

source (1-2-3) & gate (4) - 20k - 0

gate (4) & drain (5-6-7-8) 20k - 13.20

I think i measured it right.

Theres only one PQ303

[mon2]

Which mosfet was measured? Each of the measurements - especially the source - gate is showing a leak.

If you are comfortable, flux and remove this mosfet and allow it to cool on your work table. Then measure this part again while it is on your bench. This mosfet appears to be defective.

[coffeebreath]

The one circled in red, that one was tested.

[mon2]

Flux and remove it - very carefully. Do not allow for the hot air to enter the edges as this can cause the multilayer PCB to flake up the multiple layers of the laminate. Keep in tight circle and enough heat without scorching the board.

The source & gate measurement is showing a dead short. Be sure the meter is not showing OL for over limit. You can confirm by using a higher meter resistance scale -> still 0 ohms?

[coffeebreath]

source (1-2-3) & drain (5-6-7-8) 20k - 14.40

source (1-2-3) & gate (4) 20k nothing

gate (4) & drain (5-6-7-8) 20k nothing

I must have done something wrong?

[mon2]

source (1-2-3) & drain (5-6-7-8) 20k - 14.40

This is a low resistance for a working mosfet. This mosfet should be replaced.

While this mosfet is off the board, measure the resistance to ground of the drain pins (5-6-7-8). This is to confirm that the main power rail of the board is not shorted. What is the measurement?

You can either find a replacement mosfet from a donor board or order fresh compatible ones from Digikey / Mouser / Arrow and perhaps Mobile Sentrix (Toronto). Post back if you need help to locate a replacement from the stores.

[coffeebreath]

i measured the pads 5-6-7-8 on the motherboard where the mosfet used to be. im getting 0 at 20k

[mon2]

To confirm, you have one of the meter probes on any of the pins on the PCB where this mosfet was (ie. 5 6 7 or 8 is ok) and the other meter probe is to ground. Is this correct? If yes, then you have a hard short on the main power rail.

[coffeebreath]

Thats correct