Asus X453SA No Display - Charging Indicator Blinking

[binary0101]

Greetings

I got an Asus X453SA for repair
Symptom : no display, with charging indicator blinking, with or without battery. Power indicator is steady. When battery plugged in, the current consumption jumps, but the charging indicator is still blinking.

Here is the measured power sequence :

+3VA_EC +3.3V
EC_RST# +3.025V
+5VSUS_ON +3.307V
PWR_SW# +2.982V
3VSUS_ON +3.307V
SUS_PWRGD +3.386V
+1.05VSUS_PWRGD +1.061V
1.8VSUS_EN +1.873V
VSUS_PWRGD +3.383V
PM_PWRBTN# +1.830V
PM_RSMRST# +3.307V
PM_SUSC# +1.872V
PM_SUSB# +1.872V
SUSC_EC +3.292V
+1.35V_ON +3.308V
SUSB_EC# +3.290V
VDDQ_PWRGD +3.383V
ALL_SYSTEM_PWRGD +3.385V
PM_PWROK -> VCCA_PWROK +1.353V; CORE_PWROK +3.307V; DRAM_POWEROK +1.353V
BUF_PLT_RST# +3.383V

For current draw, the board is taking 270mA
The processor is heating up
I have tried to re-flash the BIOS, but it is still the same

Kindly ask for guidance
Repair guide and board view is attached

Thank You

[mon2]

Re: Asus X453SA No Display - Charging Indicator Blinking

Hi.

1) power adapter is the recommended rated unit for this laptop ?

2) Which charger IC is onboard? Locate it and share the topside markings. Perhaps will be the 'BQ' style from Texas Instruments? Also locate the 2 x DCin mosfets that will be close to the charger IC / power adapter connector onboard.

3) In the repair guide are DIODE mode readings.

Remove all power. Meter in DIODE mode.

Red meter lead, yes RED, to ground.
Black meter lead to the point to test.

Test each point they show in the repair guide and compare against your logic board to review if there is a possible fault in that area of the design.

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

Hi too, mon2

1) the power adapter is rated for the laptop(19V-1.75A-33W)
2) The charger IC is BQ735, located near the battery socket. I also located both mosfets. Haven't done "deep dive" on charging IC and DC-in mosfet.
3) Alright, will do it in the afternoon. I will post the diode mode value comparison. Also, is there any max tolerance in diode mode reading?

Thank you for the heads up, i will update this thread later on.

[mon2]

Re: Asus X453SA No Display - Charging Indicator Blinking

1) Ok. Sounds low but Asus website states the same.
2) Good.

The datasheet for the charger is on the TI website. Start with the quick review of the voltage to ground of:

REGN pin ; should be ~6 volts
ACDRV pin ; should be ~25 volts to enable the 2 x DCin mosfets

on the charger IC.

If you DO NOT see ~25 volts on ACDRV pin, then locate the series resistor on this pin which should be ~4k ohms and remove it. Do not lose this resistor. Just remove it and power up again. The confirm if the ACDRV pin is ~25 volts.

At this stage, just wanting to confirm that there are no leaky DCin mosfets and that the charger IC is working. Otherwise, a leaky mosfet could still allow for the power rails to come on.

On the DIODE mode - there is only one setting. The higher the value, the less of a chance that you have a short and vice versa. Check against the reference guide and compare against your board.

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

Good morning from Indonesia. Currently I am measuring the diode value. Will update!

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

Update : this is my measured diode mode value, compared to repair guide

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

Update :
REGN +6.05V
ACDRV 0V

Already removed the 4.7k ohms resistor, laptop is not powering up
The resistor (off board) is measured around 3.9k ohms

[mon2]

Re: Asus X453SA No Display - Charging Indicator Blinking

Measure the voltage to ground of the following pins on the BQ735 charger IC:

ACOK

ACDET

Hints are that the charger IC is defective if ACDRV is 0 volts.

Do test the mosfets that being driven by the ACDRV pin to see if they are leaky.

Remove all power. Meter in resistance mode. Check the resistance across the mosfet pins:

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. If any resistance reading is low, the mosfet is defective.

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

ACDET +2.581V
ACOK +1.577V

mosfet measurement will be updated

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

MOSFET 1
SOURCE TO DRAIN : 2.05M ohms

SOURCE TO GATE : 0.973M ohms

GATE TO DRAIN : 1.05M ohms

MOSFET 2
SOURCE TO DRAIN : 125.5k ohms

SOURCE TO GATE : 175.1k ohms

GATE TO DRAIN : 0.638M ohms

[mon2]

Re: Asus X453SA No Display - Charging Indicator Blinking

Mosfet #2 looks to be too low. Can you replace it and test again ?

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

Alright. Will update once the part comes

[mon2]

Re: Asus X453SA No Display - Charging Indicator Blinking

Also source a fresh charger IC. This is in case the ACDRV voltage does not boost as required to ~25 volts.

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

Greetings, today the parts arrived
Tried 2 charging IC and change the mosfets too
ACDRV measured around +1.3V. The 19v is not passing through the mosfets, even though i tried new mosfets..

I will update with mosfet measurement

[mon2]

Re: Asus X453SA No Display - Charging Indicator Blinking

Remove the ~4k resistor on the ACDRV pin and measure the voltage again, at the charger IC pin.

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

4k resistor is removed, measured ACDRV ~+1.3V
I will try another pair of mosfet and soruce a new charging IC

[mon2]

Re: Asus X453SA No Display - Charging Indicator Blinking

ACDET looks a bit low. From another case, we had to adjust the resistor based voltage divider so that ACDET was > 2v67.

Can you do the same?

Locate the 2 resistors that define the ACDET voltage. Then lower the R1 = resistor that mates with the adapter rae voltage.

Or increase the R2 resistor that mates to ground.

You can use an online voltage divider calculator to assist you in selecting the Vout = ACDET value.

Update: (review this thread)

https://www.badcaps.net/forum/showthread.php?t=115192

[binary0101]

Re: Asus X453SA No Display - Charging Indicator Blinking

i will try to change the value of those resistor

note:
default value-based on boardview:
R1 = 127k ohms
R2 = 20k ohms