Asus tp550ld randomly shutdown

[khelane]

Hello
The ASUS TP550LD has a sudden shutdown problem.
This device did not turn on before this problem was fixed by replacing the MOSFET PQ8802, but before the I / O heat given by another repairman, I checked the I / O bases completely, there is no problem, but now the device turns off sometimes after replacing the MOSFET or some Sometimes it turns off and on several times in a row.
Another problem with the device is that the battery charge light is always on, even when the battery is not connected.
I also tested the battery-related pins up to IC I.O and IC charging for ohmicity and connectivity, and had no problems with the resistors being the right amount.
The replaced MOSFET is exactly the same as the previous model.
The motherboard has no problems in terms of appearance and temperature.
The device is now on for 55 minutes and a full HD movie is playing, but the battery light is on while the battery is not connected at all.
Battery pins
12 volts
3.3
3.3
'GND
ALL are present
Why is the charging light always on?
ASUS TP550LD REV:2.0


TNX

[mcplslg123]

Re: Asus tp550ld randomly shutdown

What is the voltage on ACDET pin?? Which chargging IC is in use here??

[khelane]

Re: Asus tp550ld randomly shutdown

What is the voltage on ACDET pin?? Which chargging IC is in use here??

2.6 v
BQ24735 CHARGER IC

charger ic voltages :
1: 19.5
2: 19.5
3: 18.77
4: 24.17
5: 2.78
6: 2.6
7: 0
8: 3.2
9: 3.2
10: 11.25
11: 11.7
12: 12.56
13: 12.56
14: 0
15: 0
16: 6
17: 17.36
18: 12:67
19: 12.56
20: 19V

in last i don't programmed laptop

[mon2]

Re: Asus tp550ld randomly shutdown

Pin 10 is the wrong value for ILIM. Check this voltage again.

This pin may be shorting with pin 11.

Remove all power, meter in resistance mode.

Check the resistance between the pins 10 and 11.

Reading?

[khelane]

Re: Asus tp550ld randomly shutdown

Pin 10 is the wrong value for ILIM. Check this voltage again.

This pin may be shorting with pin 11.

Remove all power, meter in resistance mode.

Check the resistance between the pins 10 and 11.

Reading?

When I connect the charger to the laptop, the basic voltage is sometimes 1.5 and sometimes 0.8 volts, and after a second it reaches 11 volts.

resistance pin 10 -11 is 4.5mega ohm

[mon2]

Re: Asus tp550ld randomly shutdown

According to the datasheet, pin 10 should be a fraction of the 3v3 rail and is configured by 2 resistors acting as a voltage divider.

The voltage of pin 10 is way too high and may indicate a defective charger IC.

Review the area to locate the resistors that define this reference voltage. Higher the voltage, higher the ILIM threshold. Check against the datasheet on how this pin functions.

The external resistors on this pin should also be inspected to confirm they are not the root cause of this voltage spike.

Believe it should be replaced. Good idea to purchase spares.

Update..see table 7.1 of the datasheet. Max voltage is 7 volts for ILIM. This charger IC is now defective.

[khelane]

Re: Asus tp550ld randomly shutdown

According to the datasheet, pin 10 should be a fraction of the 3v3 rail and is configured by 2 resistors acting as a voltage divider.

The voltage of pin 10 is way too high and may indicate a defective charger IC.

Review the area to locate the resistors that define this reference voltage. Higher the voltage, higher the ILIM threshold. Check against the datasheet on how this pin functions.

The external resistors on this pin should also be inspected to confirm they are not the root cause of this voltage spike.

Believe it should be replaced. Good idea to purchase spares.

pr8819 and pr8820 are resistors connected to pin 10. Both values are correct. According to the IC datasheet, there should be 3.3 on this point, but instead it is 11 volts!
Thank you for your advice dear
After replacing the IC, the result will be announced
Is similar to this IC available?

[mon2]

Re: Asus tp550ld randomly shutdown

If you remove PR8820, do you see 11 volts where it is marked '+3VA' in the boardview file ?

Trying to determine if the 11 volt is from the charger IC that is now very likely to be defective or the external '+3VA' rail that probably has a shorted high side mosfet and the DCIN of that mosfet has yielded the 11 volts where it should have been +3VA.

Many widgets use this +3VA rail including the EC and the 11 volts would have killed these devices but continue the investigation.

[khelane]

Re: Asus tp550ld randomly shutdown

If you remove PR8820, do you see 11 volts where it is marked '+3VA' in the boardview file ?

Trying to determine if the 11 volt is from the charger IC that is now very likely to be defective or the external '+3VA' rail that probably has a shorted high side mosfet and the DCIN of that mosfet has yielded the 11 volts where it should have been +3VA.

Many widgets use this +3VA rail including the EC and the 11 volts would have killed these devices but continue the investigation.

I took PR8820, IC side 0v and 3VA side 3VOLT
After attaching the PR8820 resistor, I measured the voltage again, the IC side goes up and down from 0.8 to 2.1, but sometimes it is 1.5 volts, and the 3.3VA side is 3.290.
one question
If there is a problem with +3VA, how does the system turn on and how many hours does it work sometimes?

[mon2]

Re: Asus tp550ld randomly shutdown

Can you confirm that your meter has fresh batteries ? Perhaps replace them and then review the voltage readings again. The measurements may be off due to the accuracy of the multimeter.

[khelane]

Re: Asus tp550ld randomly shutdown

Can you confirm that your meter has fresh batteries ? Perhaps replace them and then review the voltage readings again. The measurements may be off due to the accuracy of the multimeter.

i Checked it and try new batteries .
voltage before start is 0.8 and after start 1.5volt come slow rise to 1.6 and 1.7 then few range betwen 1.5-1.7

[mon2]

Re: Asus tp550ld randomly shutdown

Ok.

1) fresh batteries on the meter are now reporting the proper voltages.

2) to save time, identify the parts you have reviewed. What the battery connector label on this logic board ?

Which mosfet is linked to the battery mosfet ?

3) Using resistance mode (remove ALL power), you should review each mosfet starting with:

ACFET (I think you have said that it has been replaced)

RBFET (reverse blocking fet)

high side mosfet for the battery charging
low side mosfet fort the battery charging

battery mosfet that enables when the logic board is powered from the battery

Once you share the battery connector details -> review the location of a potential SMBUS / I2C ESD diode. Often this is a faulty component.

[mon2]

Re: Asus tp550ld randomly shutdown

Found the requested details.

1) J6003 = Battery connector.

2) See attached. Do you have this ESD diode array on your logic board ?

PD6001 = ESD diode array used to protect the battery interface.

[mcplslg123]

Re: Asus tp550ld randomly shutdown

Acok(pin5) seems bit low.Should be 3.3V. Check acok voltage divide resistors.

[mcplslg123]

Re: Asus tp550ld randomly shutdown

Try Replacing R2 in the ac det voltage divider,even if the value is correct.If that don't help, try lowering the value of R2 resistor a bit(say 5% less value).But don't try value which is way below specified, only 5% difference,not more than that.

[khelane]

Re: Asus tp550ld randomly shutdown

Found the requested details.

1) J6003 = Battery connector.

2) See attached. Do you have this ESD diode array on your logic board ?

PD6001 = ESD diode array used to protect the battery interface.

Sorry, I could not answer in time
Yes PD6001 available

I will do the mentioned tests for you tomorrow

[mon2]

Re: Asus tp550ld randomly shutdown

Remove PD6001 and test to see if it makes a difference on your logic board.

[khelane]

Re: Asus tp550ld randomly shutdown

Remove PD6001 and test to see if it makes a difference on your logic board.

I removed the PD6001 but nothing happened

try again charger ic voltages :
1: 19.5
2: 19.5
3: 18.77
4: 24.17
5: 2.78
6: 2.6
7: 0
8: 3.2
9: 3.2
10: 1.6 -1.7 (few rang)
11: 11.7
12: 12.56
13: 12.56
14: 0
15: 0
16: 6
17: 17.36
18: 12:67
19: 12.56
20: 19V

[khelane]

Re: Asus tp550ld randomly shutdown

Acok(pin5) seems bit low.Should be 3.3V. Check acok voltage divide resistors.

Inside the ic data sheet on page 3, the required voltage of acdet is 2.4 to 3.15. The read voltage is 2.6 (I don't think there is a problem)

[khelane]

Re: Asus tp550ld randomly shutdown

I removed the PD6001 but nothing happened

try again charger ic voltages :
1: 19.5
2: 19.5
3: 18.77
4: 24.17
5: 2.78
6: 2.6
7: 0
8: 3.2
9: 3.2
10: 1.6 -1.7 (few rang)
11: 11.7
12: 12.56
13: 12.56
14: 0
15: 0
16: 6
17: 17.36
18: 12:67
19: 12.56
20: 19V

I already replaced the PQ8802

Ohm check mosfet's:

PQ8803 == D--S :275K G--S :6MEGAOHM G---D :5.6MEGA
D---GND :98K S---GND :460K GATE----GND :OL

PQ8804== D--S :480K G---S :171K G----D :600K
D---GND :270K S---GND=0HM GATE--GND : 172K

PQ8805 == D--S :480K G---D=600K G---S: 200K
D---GND : 98K S---GND :270K GATE----GND:600K