Dell Inspiron 7567 LA-D993P Battery percentage

[rob777]

Hi guys looking for some help. Losing my mind over an old machine I'm trying to get going and cannot. It's a Dell Inspiron 7567 LA-D993P.

Problem was it was not charging. One of the dc-in mosfets had died. So I replaced all 5 of the 6 mosfets in charging circuit. Also replaced bq charging ic.

Laptop powers on and recognises charger but battery percentage never increases. Laptop will run on battery power only but can't get past 4%.

I've uploaded the schematics if anyone can help. Page 55. [MOD EDIT] Link to schematic -> https://www.badcaps.net/forum/troubl...ematic-request

Hopefully I can get this going again. Really appreciate any help given.

[mon2]

The battery gauge is handled using the smbus scl and sda lines on the battery pack. Measure the voltage to ground of each of these important lines, scl and sda. Post each measurement.

[rob777]

The battery gauge is handled using the smbus scl and sda lines on the battery pack. Measure the voltage to ground of each of these important lines, scl and sda. Post each measurement.

Thank you. SCL and sda measure .418 and .465. That's diode mode red probe on ground.

After more probing I've found PQ304 isn't opening. I have 19v coming in. Nothing coming out and 11.01v on enable pin DH_CHG. Betting this is bleeding obvious and staring me in the face.

[mon2]

Diode mode checks are ok. So these lines are not shorted.

Check your high side mosfet in resistance mode. Remove all power. Meter in resistance mode.

Check the resistance across this mosfet:

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. A low resistance reading often means the mosfet is shorted / leaky and must be replaced.

[rob777]

Thank you. PQ304 high side mosfet is one of the ones I have already replaced.
Source to gate - 480k
source to drain - 390k
drain to gate - 200k

PQ305 the smaller mosfet which sits underneath and is connected to PQ304 has not been replaced. It's readings are:

Source to gate - 198k
source to drain - 42k
drain to gate - 440k

Is that 42k resistance too low and showing that pq305 needs to be replaced?

[mcplslg123]

PQ301/302-Voltage on Source/gate/Drain?
Cgarging IC-VCC/REGN?CMSRC/ACDRV/ACOK/ACDET-Voltage on these pins?

[rob777]

PQ301/302-Voltage on Source/gate/Drain?
Cgarging IC-VCC/REGN?CMSRC/ACDRV/ACOK/ACDET-Voltage on these pins?

Thank you. Voltages measured:
pq301 19.3/25.5/19.3
pq302 19.3/25.5/19.3

pin 28 vcc 19v
pin 24 regn 6.09v
cmsrc - 19.27
acdrv - 25.5
acok - 3.353
acdet - 2.671

from what I understand reading the laptop charging circuit sticky is all these voltages are correct? ACDET the only one I'm not sure what that voltage is supposed to be or whether correct.

[mon2]

Yes 42k looks low. Consider to flux and remove this mosfet. Then allow it to cool on your work table. Measure the resistance again of this removed mosfet. Do not power up the logic board without a low side mosfet. Compare the resistance to a fresh mosfet.

[mcplslg123]

Measurements at post#7 are all correct. ACDET should be above 2.6V

[mon2]

Is this Dell power adapter the proper one for this chassis? You could modify the resistor based voltage divider so that the ACDET pin will rise above 2v7 (check the datasheet for the charger for this threshold value) to pacify the detection circuit but in theory it should not be required.

[rob777]

Yes 42k looks low. Consider to flux and remove this mosfet. Then allow it to cool on your work table. Measure the resistance again of this removed mosfet. Do not power up the logic board without a low side mosfet. Compare the resistance to a fresh mosfet.

I have removed mosfet. Gate to source and gate to drain I cannot get a reading on. OL both ways.
drain to source is 12.3m ohms.
I don't have another mosfet to compare with. Going to have to purchase something and hope this is the issue.

The PQ305 is a AON7518 of which I can't find a data sheet and is also obsolete however on digi key it says the AON7380 is a direct replacement for the 7518.
Then I find the 7380 is also obsolete. Comparing data sheets aon36368 is similar. I have attached both data sheets. Can I get confirmation it will be sufficient to use 36368 in its place? Thanks again for everyone's help.

[rob777]

Is this Dell power adapter the proper one for this chassis? You could modify the resistor based voltage divider so that the ACDET pin will rise above 2v7 (check the datasheet for the charger for this threshold value) to pacify the detection circuit but in theory it should not be required.

started with a little 90w charger. Then used a 180w and still unsure I bought a 240w charger. No changes with any of the reading around the bq chip with any of those chargers. These are not original chargers though.

[mon2]

Does the bios report that a different power adapter is plugged in?

review the voltage to ground of each pin on pq100. Post each measurement.

dell adapters use a single wire communication to identify the power adapter. This is the PS_ID line.