AN515-54

[mohamed zahir]

Please me me diagnose my laptop acer nitro 5 I have multimeter and 0 knowledge so please try to be very precise this motherboard numbers REV 1A EH5VF there is some voltage but very low in mv but maybe I am testing wring

[mohamed zahir]

This where I am right now

[mon2]

See attached. Carefully lift up the white sticker and share the full part number on the board. This will be the LA-Hxxxx silk screened markings. We need to confirm this detail.

What is the history of this unit? Any liquid damage? Just stopped working one day?

[mohamed zahir]

https://youtu.be/ha04VVPChjQ?feature=shared same exact this one check if something burnt. No liquid damage but heavy usage maybe something got burnt. One day is just stopped working

[mon2]

Configure your meter to DC mode but at 20V or higher. We need to check if the external power adapter is OK or not.

Locate the power connector on the board. Mate the adapter to the logic board.

Carefully check for the adapter voltage. Black meter lead to ground - metal shield is ok on the board. Red meter lead to the power connector. Share pics of the board if not sure but there will be a few inductors / coils nearby the same DCin power connector. We are only confirming if the circuit board is able to receive the ~19v from the power adapter. If not, the power adapter is a suspect and should be replaced with another for testing.

[mohamed zahir]

The red probe where do I connect can you place arrow

[mon2]

See attached.

[mohamed zahir]

I got a reading of 0.20 max but voltage seems to be decreasing each time I test it

[alfredposadas09]

I got a reading of 0.20 max but voltage seems to be decreasing each time I test it

do you have 20v on the charger?

[mon2]

Use the 20V setting on your meter - see attached. Then attempt to measure again. If this voltage is not a stable ~19v then the power adapter is defective and the logic board should be tested with another. You can use almost any laptop power adapter here for testing. The voltage is very common to other laptop chargers.

[mohamed zahir]

The adapter output is 19v. I tested with the multimeter on 20v it showed 0.26 at the start and gradually decrease to 0 i will try to get a new adapter to check if problem with adapter or board

[mon2]

If possible, take a picture of the meter in this setting while you see the 0.26 measurement. The voltage does not sound correct and should be ~19.xxx or ~18.xxx. From the shared details, it appears that you have a voltage under 1 volt where 0.26 = 260 mV. This is very low and confirms the adapter is defective.

Test with a known good adapter to continue. Post your updates here. The fault may be only that the power adapter is defective.

[mohamed zahir]

Showing 0.33 I will try to get new adapter

[mon2]

Yes, agreed. On the 20v scale, this measurement is showing 0v33 or about 1/3rd of a volt. Certainly not enough to power even a LED let alone the logic board. It appears that the power adapter is defective.

[mohamed zahir]

Power adapter is working fine. Went to a shop and tried a different 19v adapter same voltage 1.7 and gradually decreasing. Seems there is a shortage in the board

[mon2]

Remove all power. Disconnect this adapter and also the battery (if it is connected).

Configure the meter into resistance mode (use the 2k ohms scale for now). See attached.

Test the resistance to ground of the same pins as before. We are testing if there is a short on the DCin power path.

What is the resistance measurement?

[mohamed zahir]

All 3 pins give 0.532 on the 2kohms scale

[mon2]

This is a low resistance to ground at this part of the logic board.

0.532 on the 2kohms scale means the resistance is @ 532 ohms = 532R. While this is not a hard short like 0 ohms or similar, the resistance is of concern.

The next stage of testing will be of the DCin mosfets @ PQB11 and PQB12.

Configure the meter to a higher resistance scale of 2Mohms (highest on your meter).

Then measure the resistance across the PQB11 mosfet:

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

You can pick any pin from the group of pins (1-2-3) - pick any pin.

We are checking if there is a low resistance. A good mosfet will have hundreds of k ohms of resistance or higher. If the resistance is lower, the part is likely to be defective. Then you will need special tools to remove and replace the part. Suggest to work with a local cell phone tech who is comfortable with board level repairs.

[mohamed zahir]

Spent maybe 30 mins trying to find either one. Can you help me find it.

[mon2]

Locate the chip with 'PUB1' in the white silk screen. This square chip is near the battery connector which you have disconnected. This is the charger IC. Next, check on the opposite side of this area to confirm if the mosfets are perhaps soldered on the bottom side of this same region.