Asus x442u cant use adaptor

[Yosua]

hi friends, I hope someone can help me with my problem on this asus x442u board, namely when using the adapter it can't turn on but using battery voltage it can turn on, and on this mobo using the bq25780s ic, after I measured the 19v acfet it didn't want to cross and at the gate pin 4 acfet also does not appear 24v.


this is for temporary measurements on this bq24780s ic

VCC : 19V
ACDET:2.6V
REGN:6V
ACOK:5.2V
ACDRV:0.14V

thank you I hope someone can give me direction.

I'm also attaching a boardview.

[mon2]

Re: Asus x442u cant use adaptor

Hi.

1) remove all power. Meter in resistance mode. Check the resistance across each front side mosfet.

Source and drain
Source and gate
Gate and drain

Look for low resistance values which means the mosfet is damaged.

2) quite possible the charger ic is damaged and needs to be replaced as the gate charge pump is not working.

First check all conditions needed to enable the gate and that the mosfets are not defective.

VCC : 19V
ACDET:2.6V
REGN:6V
ACOK:5.2V

Look ok.

What is the exact markings on the charger IC?

Is it bq25780s or bq24780s ?

Post the voltages on the SDA and SCL lines.

[Yosua]

Re: Asus x442u cant use adaptor

Hi.

1) remove all power. Meter in resistance mode. Check the resistance across each front side mosfet.

Source and drain
Source and gate
Gate and drain

Look for low resistance values which means the mosfet is damaged.

2) quite possible the charger ic is damaged and needs to be replaced as the gate charge pump is not working.

First check all conditions needed to enable the gate and that the mosfets are not defective.

VCC : 19V
ACDET:2.6V
REGN:6V
ACOK:5.2V

Look ok.

What is the exact markings on the charger IC?

Is it bq25780s or bq24780s ?

Post the voltages on the SDA and SCL lines.

May I ask, is it true that ACOK for normal conditions is 5.2v?


I think this pin should have a voltage of 2.8v?

correct me if i'm wrong

[Yosua]

Re: Asus x442u cant use adaptor

ohh I'm sorry, the correct one is bq24780s

[mon2]

Re: Asus x442u cant use adaptor

According to the TI datasheet for this part, ACOK is an open-drain output.

So if ACDET > 2v4 then this ACOK will be floating. It is upto the external pull-up resistor to define the 'high' value. The pull-up voltage of 5v0 is fine for this pin to be considered OK.

[Yosua]

Re: Asus x442u cant use adaptor

According to the TI datasheet for this part, ACOK is an open-drain output.

So if ACDET > 2v4 then this ACOK will be floating. It is upto the external pull-up resistor to define the 'high' value. The pull-up voltage of 5v0 is fine for this pin to be considered OK.

thanks for your direction, i'm too equating it with other boards and i also see other treads for shuffle measurement many use 3.3v for ACOK on this ic, i'm sorry

and for SDA & SCL PIN both 0v bro

I've also replaced acfet with a good one but it's still the same

[mcplslg123]

Re: Asus x442u cant use adaptor

I've never seen ACOK at 5.2V on BQ24780(S). It should be 3.3V as the pull up resistor is always from 3.3V ACDRV will work only when CMSRC is 19V. So do check that. Is there 19V on charging Coil??

[Yosua]

Re: Asus x442u cant use adaptor

I've never seen ACOK at 5.2V on BQ24780(S). It should be 3.3V as the pull up resistor is always from 3.3V ACDRV will work only when CMSRC is 19V. So do check that. Is there 19V on charging Coil??

thank you for taking your time to help me, then at what parameter is the volts when ACOK is on high?


the charging coil only shows 0.23v bro.

[mon2]

Re: Asus x442u cant use adaptor

Post the voltage on each pin of the charger IC when the dc adapter is attached (no battery).

[Yosua]

Re: Asus x442u cant use adaptor

Post the voltage on each pin of the charger IC when the dc adapter is attached (no battery).

This is the measurement of the adapter attached and without battery

1.acn = 5.61v
2.acp = 5.61v
3.cmsrc = 0.18v
4.acdrv = 0.21v
5.shuffle = 5.51v
6.acdet = 2.6v
7.iadp = 0.03v
8.idchg = 0.01
9.psys = 0v
10.prochot = 0.03
11.sda = 0v
12.scl = 0v
13.cmpin = 0.32v
14.cmpout = 6v
15batpres = 0v
16.tb status = 0v
17.batsrc = 0.23
18.batdrv = 0.23v
19.srn,20.srp = 0.23v
21.ilim = 1.12v
22.grd
23.lg = 0v
24.regn = 6v
25.bst = 5.97v
26.hg = 0.23v
27.lx = 0.24
28.vcc = 19.1v

[mon2]

Re: Asus x442u cant use adaptor

Confirm the voltages on pins 1, 2 and 3 again for the charger IC.

The SDA and SCL lines are missing their pull up voltage. Trace these lines to the local pull up resistors. The other side of each resistor will go to an always on rail of 3v3.

That regulator is not working to supply the missing rail.

[Yosua]

Re: Asus x442u cant use adaptor

Confirm the voltages on pins 1, 2 and 3 again for the charger IC.

The SDA and SCL lines are missing their pull up voltage. Trace these lines to the local pull up resistors. The other side of each resistor will go to an always on rail of 3v3.

That regulator is not working to supply the missing rail.

thanks bro, but indeed pins 1,2 and 3 the voltage remains the same, does that mean the sda and scl lines are broken?

and under what conditions those sda and scl pins appear?

[Yosua]

Re: Asus x442u cant use adaptor

I found a 6 pin diode parallel to 2 resistors connected to the sda and scl lines, and on pin number 5 there is +3va and on pin 3,4 is the source of sda 0v and scl 0v too

[mon2]

Re: Asus x442u cant use adaptor

No. The I2C (SMBUS) SDA & SCL lines are not broken but each should have a pull-up resistor. The other side of each resistor should be pulled up to +3v3.

The +3v3 rail is missing.

1) See attached. The schematic for this logic board looks to be very close to yours for the charger IC. This should help for this case.

2) Check the resistor values for the requested parts. Remove all power. Meter in resistance mode. Measure each resistor value.

[mon2]

Re: Asus x442u cant use adaptor

Post a picture of the DIODE you are referencing and will see it can be found in the schematic.

Where is it on the boardview file ?

Need to get ready for work...will continue at the office.

[Yosua]

Re: Asus x442u cant use adaptor

Post a picture of the DIODE you are referencing and will see it can be found in the schematic.

Where is it on the boardview file ?

Need to get ready for work...will continue at the office.

is the schematic you gave is suitable for this board?

the diode is at the top of the board near the battery connector and the code for this diode is PD6001 bro.

okay I'll wait when you're at the office

[Yosua]

Re: Asus x442u cant use adaptor

Post a picture of the DIODE you are referencing and will see it can be found in the schematic.

Where is it on the boardview file ?

Need to get ready for work...will continue at the office.

Is the source of sda and scl +3va on pin 5 of the diode?

because i measure on kbc also no voltage output for sda and scl . lines

[Yosua]

Re: Asus x442u cant use adaptor

No. The I2C (SMBUS) SDA & SCL lines are not broken but each should have a pull-up resistor. The other side of each resistor should be pulled up to +3v3.

The +3v3 rail is missing.

1) See attached. The schematic for this logic board looks to be very close to yours for the charger IC. This should help for this case.

2) Check the resistor values for the requested parts. Remove all power. Meter in resistance mode. Measure each resistor value.

you are right bro, the source of sda and scl is +3va_ec which is on the RN305 near EC, after I measured it turned out that +3va_ec was indeed missing

[mcplslg123]

Re: Asus x442u cant use adaptor

+3V LDO will be missing as perhaps 19V is not passing thru on this board. Since 3V PWM is not getting +19V as VIN ,it cant produce +3V LDO. So dont bother about SDA/SCL at this moment. You need to check why charging IC ACP/ACN is not 19V. Thats the 1st step for repairing this mb. Stay focussed on this issue alone till you fix it.

[Yosua]

Re: Asus x442u cant use adaptor

+3V LDO will be missing as perhaps 19V is not passing thru on this board. Since 3V PWM is not getting +19V as VIN ,it cant produce +3V LDO. So dont bother about SDA/SCL at this moment. You need to check why charging IC ACP/ACN is not 19V. Thats the 1st step for repairing this mb. Stay focussed on this issue alone till you fix it.

ok thanks sir.. i will focus on acn and acl first..., then on which parameters should i check first sir?