Acer - N19C2 - MB EH7LW - Sudden death

[mon2]

ACDET now is a good voltage to announce that the adapter is connected.

However, SDA and SCL should not be at 0 volts on this charger IC.

The SMBUS lines will be used by the EC to configure specific registers inside the charger IC.

Confirm that the pull up resistors on the SDA and SCL lines are being pulled up to +3v3. One side of the resistor will be to SDA line, other side must be to +3v3. The same for the SCL line.

[Adenitz]

Originally Posted by samstown

Hello, ACDET = 2.64V, is this a good thing ?

This you can calculate yourself, since ACDET is defined by voltage divider. On the schematics page 36, you can calculate this voltage as: 19*66.5/(66.5+422) and that is about 2.6V

Pull up resistors for SDA (data) and SCL (clock) can be found on page nr 5. These are should not be zero. There are 2.2 kohm resistors connected to 3.3V

[samstown]

Thank you.

SDA and SCL are going to pull-up then to the battery connector.

With power supply only = 0V all way
With PS and Battery = 0V all way.

So that PUB1 is the problem ?

[mon2]

No. See attached. The PULL-UP voltage is missing and this rail is linked to PU301 IC.

Specifically, it is the LDO output @ pin # 16 & 17. For this rail to ENABLE, the pin # 11 of the same IC needs to be a logic high (~+3v3).

So measure and post the following:

a) voltage that should be the INPUT to PU301 IC. Expecting to hear you have ~19V = DC adapter voltage.

b) voltage on the ENABLE pin # 11 (EN2). Should be ~3v3 to turn ON the LDO.

c) voltage @ pin 16 & 17 for the LDO output. Most likely this will be 0V as you have already measured but post your readings.

Update:

Posted the schematic that confirms that the +3VLP = +3VLP_ECA.

[samstown]

Thank you ! Happy you are here.. this is complex.

a) PU301 PIN 2,3,4,5 = 0 V .... 19V expected
b) ENLDO_3V PIN 11 = 0 V
c) 16 & 17 = 0V

[samstown]

Is there anything else i should check ?

[mon2]

Connect the adapter. What is the voltage reading of coil PL301 (first post) ?

Check pads # 1 and # 2 of this component.

[samstown]

Thanks. 0V on each pads of PL301.
So where is this 19V suppose to come from. I see PL301 on diagram... but it's connected to 19V.

[samstown]

PDB1 has 0 on Pin 2 or 3 (not sure wich one is 2 or 3) and 19 on 1 and on the other one.

So, one of the two +19Vin or +19VB is missing

[mon2]

PDB1 is a sot-23 packaged dual diode device with a common cathode. The cathodes are tied together and this is pin #1. Hence the name, common cathode.

The diode passes the voltage only in one direction and blocks in the other direction. Flows from anode to cathode.

The physical part will have 2 pins on one side; a single pin on the other side (pin #3).

Pin #1 of this part is mated with the adapter dc input voltage. Whatever is the dc in voltage, this voltage will be on pin #1 of the PDB1 component.

Pin #2 will be voltage after the first 2 mosfets. This same voltage will be used to power the logic board.

So the way the dual diode is drawn in the schematic is the way the physical part is soldered on the logic board. Always consult the component datasheet for the full details.

For your case, this power rail (+19VB) is not working and respectively does not appear on PL301 as well.

If the power adapter is not used but a good battery is attached, then the battery mosfet should turn on and power the logic board. The charger IC will be powered by the dual diode at PDB1, pin #2 = +19VB.

[Adenitz]

samstown, when you remove all power (DC IN and battery), measure resistance between one pad of PL301 and ground.

[samstown]

Thank you Adenitz. PL301 to GND = 0 ohm on both side. It beeps on both side. So need to replace this coil then. Thank you !

[samstown]

After removing PL301, one Pad is no longer shorted. The other one still. That's the one going to PUB301 PIN 2,3,4,5. Looks like this is not normal.

[mon2]

Very good. There are 5 capacitors on the rail going to PU301 IC, pins 2-3-4-5.

One of these capacitors is shorting the line to ground.

Visually inspect for any off color capacitor in this group. My guess is that it will be one of the 10uf parts. Apply flux and carefully remove one of the caps. After it is removed, check if the short is removed. Repeat till the bad cap is found. Post your results.

If the removed part is not the guilty party, it should be ok to place it back but suggest to remove each till found.

[samstown]

Thank you !

It was the medium cap (I am seeing 3 only, two small, one medium). I can put coil back ? And I need to replace the shorted cap ? There's no indication of value, can I try to take a similar cap size from another mb (how can I know which pad goes where... or it doesn't matter ) ?

[mon2]

Yes, place back the coil that was removed from PL301.

Then with the power off, check the resistance to ground again to confirm there is no short circuit.

Leave off the shorted cap.

Test the logic board with the adapter. Post your results.

The missing shorted cap is not critical but can be replaced with another. Since this rail works at 19 volts, the cap MUST be rated at higher than this value. For example, 25 volts.

You should be able to locate a ceramic capacitor at 10uf, 25 volt and 0603 in body size which are preferred since they are not polarized. Such parts can be soldered in either direction.

Post a pic of the bad capacitor. Perhaps it was a polarized tantalum capacitor?

[mon2]

Correcting my pin #s from an earlier post:

PDB1 is a sot-23 packaged dual diode device with a common cathode. The cathodes are tied together and this is pin #1. Hence the name, common cathode.

The diode passes the voltage only in one direction and blocks in the other direction. Flows from anode to cathode.

The physical part will have 2 pins on one side; a single pin on the other side (pin #1).

Pin #3 of this part is mated with the adapter dc input voltage. Whatever is the dc in voltage, this voltage will be on pin #1 of the PDB1 component.

Pin #2 will be the voltage sourced from after the first 2 mosfets. This same voltage will be used to power the logic board.

[samstown]

Thank you. It's looking much better. The charging Led is orange now. When I try to turn it on the other LED goes blue.. then off. I see nothing on the screen yet.

I'll check all cabling.. it's promissing.

[samstown]

You guys rock ! So cool !

Thank you !!! I'll finish rebuilding and post tomorrow.

[mon2]

Excellent! Well done.

This one was @Adenitz - good catch on the PL301 line short!!