u36sd rev2.1 - chg_en# 0v battery only!

[infordecima]

Good evening, my asus u36sd rev2.1 always has the orange charging LED on when I have the battery inserted, without the charger inserted, without the battery I have chg_en# at 3v everything is fine but when I insert the battery I only have chg_en# to 0v when in reality it should have 3v.

b24740

help

[mon2]

The net name label has a ‘#’ suffix which means this is an active low signal. So when this signal is at 0 volts = logic low, the battery is considered to be attached and vice-versa.

[infordecima]

Bom dia, sim, eu sei disso, o problema é que a bateria só está conectada sem um carregador acoplado e o chg_en# está em 0v, quando deveria estar em 3v.
Does the value of chg_en# come from ic bq or kbc (ec)?

[rogfanther]

English, please.
The signal is right if the battery is inserted.
You seem to have problem with the ac adapter detection. Measure voltages around the BQ chip.

[infordecima]

bq24740

No battery connected to charger but PC turned off

1- 3.30
2- 18.45
3- 18.45
4- 0
5- 2.63
6- 1.15
7- 0
8- 0
9- 0
10- 3.30
11- 3.30
12- 0
13- 0
14- 1
15- 0
16- 0
17- 1.06
18- 1.06
19- 1.06
20- 3.16
21- 1.74
22- 0
23- 0
24- 5.95
25- 1.06
26- 1.06
27- 5.84
28- 18.81

with battery only connected and PC turned off (orange charging LED on)

1- 0v
2- 15.45
3- 15.45
4- 0.15
5- 0
6- 0
7- 0
8- 0
9- 0
10- 0
11- 0
12- 1.31
13- 3.31
14- 0
15- 0
16- 1.95
17- 15.67
18- 15.67
19- 15.67
20- 0
21- 1.09
22- 0
23- 0
24- 0.20
25- 15.65
26- 15.65
27- 15.65
28- 7.56

[mon2]

Check your diode feeding into pin #28 (Vcc) from the battery. The voltage is too low here for the battery only case.

[infordecima]

passes through a capacitor and goes to the diode image below

[mon2]

Trace the voltage to ground of the battery on each leg of the diode that feeds onto pin #28 (Vcc). With only the battery attached, the battery voltage should only drop by 0v6 or similar to pin #28. Also this voltage should not reverse leak onto power adapter side of the power path.

What is the voltage of the raw battery? See ~15v on a few pins and expecting a similar voltage on pin #28.

[infordecima]

with grounding on the battery and measuring the diode pins, same voltages as the image above, pin 1=0.43, pin 2=0.43v, pin 3=7.48v

battery is 15.59v and I measured the battery pins with it connected,
I have 15.59v on the pin
8 and 9
and 3.33 in 4 and 5.

[infordecima]

with grounding on the battery and measuring the diode pins, same voltages as the image above

battery is 15.59 and I measured the battery pins with it connected, I have 15.59 on the pin
8 and 9 and 3.33 in 4 and 5

I don't know where the 7.53v comes from pin28

Please note that the computer turns on and works only when the orange LED charging light is always on, even without a charger placed with an indication in the windows that it is charging.

[mon2]

Ok. The battery voltage is now confirmed and appears to be OK.

Which diode is taking this voltage to power the charger IC @ pin #28?

Is it PD8802? If yes, one leg of this dual diode must be at the same voltage as the battery voltage = ~16v to ground.

Then pin #28 must receive about the same voltage as the battery voltage (battery voltage - 0v6 for the diode forward voltage drop). If pin #28 is must lower, then PD8802 is defective.

[infordecima]

It goes through the pd8802 but it shouldn't be the one sending the battery voltage, maybe the pq8804?

The pq8804 seems to me to come from the vin (charger) and another battery pin.

The PD8802 pins 1 and 2 (0.46v) are connected.

The pr8829 is not on the board, it must come from the factory like this.

The second image is pin 28 vin of the load bq that will connect to pin 3 pd8802

[mon2]

Ok. Confirm that pins # 1 & # 2 on PD8802 have the same battery voltage of ~15v59 volts.

Then pin #3 on PD8802 should be about 0v6 lower than the input voltage so around 15v on pin #28 of the charger IC.

If not, then PD8802 should be replaced. Since Asus schematics are in the witness protection program, the schematics are rare. You will need to trace out this region of the circuit and post all details here. Which exact part / diode mates to pin #28 (Vcc) of the charger IC. Assuming it is PD8802 or another, the voltage should not be so low when you attach the battery on the Vcc pin.

[infordecima]

pin #1 and #2 of the PD8802 have 0.46V and #3 7.48v when it should have 15v, as this pin goes to pin #28 of the load ci.

I'm going to replace the pd8802 to check if the #3 voltage goes up.

[mon2]

Hunt for the diode that has the battery voltage on pins 1 or 2. That is the diode of interest. It is not this one since you have a very low voltage at pins 1&2. You can remove it to see if this part is reverse leaking.

[infordecima]

I didn't find any diode in the charging bq power circuit, just that pd8802 is normal?

Now I don't know where the 7.53v from the pd8802 comes from.

I already changed the pd8802 and the behavior remains

I attach the boardviewer to help me please