Asus FX504 not charging battery

[mon2]

Re: Asus FX504 not charging battery

No, do not short the mosfets.

Remove the battery.

Apply the external power adapter that should be the original and recommended unit for this laptop.

Measure the voltages for the DCin mosfets. Post the readings for each mosfet,

Source
Gate
Drain

Also interested in the charger IC voltage readings.

For the TI BQ charger series, ACDRV should be ~25v so that the 2 x DCin mosfets enable to pass through the adapter voltage. This voltage should be on the gate pin #4 of the N-channel mosfets when the adapter is plugged in to the logic board. If the voltage on pin #4 is not this value, then some condition is not being met for the charger IC or the charger IC is defective or not soldered properly if it was replaced.

[Roll]

Re: Asus FX504 not charging battery

OK, original ASUS 150W adapter that shipped with this laptop connected, battery disconnected.
PQ21
D: 19,95 V 75 kohm to gnd
S: 0 V about 8 Mohm
G: 0 V 3,4 Mohm

PQ22
D: 0 V 200 kohm
S: 0 V
G: 0 V 5,5 Mohm

ACDET - 2,7 V
CMPIN - jumping around 0,165 V
CMPOUT - around 0,170 V
BOOT - 0,126 V
VCC - 20 V
others are 0 or almost 0. There are no shorts to GND on this IC

[mon2]

Re: Asus FX504 not charging battery

What is the voltage on the following pins of the charger IC?

ACDRV
REGN

[Roll]

Re: Asus FX504 not charging battery

They are both 0 V.

[mon2]

Re: Asus FX504 not charging battery

Remove all power. Meter in resistance mode.

Measure the resistance to ground for the REGN pin.

One meter lead to REGN, other lead to ground.

Post the reading.

Repeat for ACDRV.

If the readings are not low resistance, the charger IC is defective and must be replaced.

The REGN should be ~6v when this chip is powered by the battery or external power adapter. Confirm again that it is receiving the voltage on the VCC pin.

[Roll]

Re: Asus FX504 not charging battery

Oh my god, you are the best. I checked it - no short on those lines, so I replaced the charging IC again and now it works AND charges!
So the first IC was faulty. Good thing I ordered two of them.

[DavidRM]

Hi all

I have followed this topic because I have the same problem.

Laptop can work without battery as desktop computer.
If I connect the battery and I plug the AC adapter, power supply overpower protections triggers and the voltage from the AC adapter drops from 19V to 0V.
I turn on my computer with the battery and If I plug AC adapter it is not detected, but it can be detected sometimes without any reason. When It was detected It worked properly

My board is DABKLGMB8D0 REV D

I have replaced PQ21 because source, drain and gate were shorted.

After that laptop detected the AC adapter when it was plugged but the battery did not charged.

I have replaced IC, PQ22and PQ23, but now the computers does not power on.

The datasheet has this block diagram that with the blocks related with the problem that I have.



When I plug the AC adapter IC pin have the following voltages in the pin showed in the previous image,
VCC 19.34
ACDET 2.66
ACOK 0.05
ACDRV 0.28
CMSRC 0.3

Datasheet says that if ACDET is higher than 2.4 and VCC is higher than UVLO (which is very low, about 3V), ACOK should be high and ACDRV should be 25V. Since it was mentioned before REGN voltage is 6.6 which is OK. I do not know what is happening and why the laptop cannot work only with the AC adapter.

I have replaced the IC and some MOSFETS with new ones. I do not if they are fake and bouce of that is is not working.

Thanks for your help

[mon2]

Is the charger suitable to power this laptop? Some gaming laptops are pigs on the current draw.

What is the voltage to ground of REGN (the schematic has a typo name of RENG) pin # 24 on the charger IC? It should be ~6 volts.

Suggest to flux and remove PQ20 off the board to remove it from the equation. Be sure your power adapter is of the proper polarity and suggest the original Asus.

Moving forward, carefully flux and remove PR198 off the board if you are comfortable. Do not lose this part. Power up again. Do you now see a boosted gate voltage on the removed SMD resistor pad that is mated to pin # 4 on the charger IC? It should be ~25 volts.

[DavidRM]

Is the charger suitable to power this laptop? Some gaming laptops are pigs on the current draw.

What is the voltage to ground of REGN (the schematic has a typo name of RENG) pin # 24 on the charger IC? It should be ~6 volts.

Suggest to flux and remove PQ20 off the board to remove it from the equation. Be sure your power adapter is of the proper polarity and suggest the original Asus.

Moving forward, carefully flux and remove PR198 off the board if you are comfortable. Do not lose this part. Power up again. Do you now see a boosted gate voltage on the removed SMD resistor pad that is mated to pin # 4 on the charger IC? It should be ~25 volts.

Voltage in REGN is 6.6 V(you can see it in my first message).

Charger is correct I have another one from MSI which can be suitable in this case. Both have same polarity.

My board does not have Reverse Input Voltage Protection circuit.

I do not have any problem to remove that resistor but as my laptop does not have that protection that I mention I pretty sure that the problem has a different origin.

I can try but I have measure ACDRV-1 (before resistor and it is the same)

Thanks

[mon2]

ACDRV voltage will be shunted if the DCin power path mosfets are defective. That is the reason to remove the ACDRV resistor that is in series with the gate pins.

What is the resistance to ground of ACN on the charger IC?

What is the full path resistance between pins ACP (2) and ACN (1) on the charger IC? Measure directly at the charger IC without any power to the board.

Suggest to test the resistance across the DCin mosfets:

source / drain
source / gate
gate / drain

for each.

[DavidRM]

ACN GND 12 Mohm
ACN ACP 1.3 Mohm

PQ21
source / drain 1.6M
source / gate 1.6M
gate / drain 1.4M

PQ22
source / drain 1.8M
source / gate 1.6M
gate / drain 1.4M

[mon2]

ACN ACP 1.3 Mohm

Can you confirm this measurement again? This path should be close to 0 ohms. Touch your meter probes together, what is the resistance? This measurement should be close to the same reading.

If not, there is a break in this critical resistance path. For such a case, continue to leave in resistance mode and trace out this path from ACP leg to the current sense resistor @ PR192. Then repeat for ACN leg to PR192. Each should be ~0 ohms.

[DavidRM]

I have replaced IC charger, there were some shorts

I have repeated all the measurements:

PR198 removed and voltage remains 0

ACN ACP 0.5 ohm
ACN GND 1M ohm (changes depending on the scale)

PQ21
D: 19,95 V 75kohm to gnd
S: 0 V 2.4 Mohm
G: 0 V very high

PQ22
D: 0 V 300 kohm
S: 0 V 2.4 Mohm
G: 0 V very high

[mon2]

ACN ACP 0.5 ohm

If you touch your meter probes together, what is the resistance? Assuming that it is also ~0R5 ohms? In this case, the measurement is correct.

Apply the ACDRV resistor back onto the board.

Attach the power adapter. Carefully measure the voltage to ground of each pin on the charger IC.

Post each measurement with the pin # and function label for the charger IC.

[DavidRM]

I use different probes with resisiance of 0.5 ohms

ACN 3 drops to 0
ACP 3 drops to 0
CMSRC 0.02
ACDRV 0
ACOK 0
ACDET 2,6
IADP 0
IDCHG 0
PMON 0
PROCHOT 0
SDA 0
SCL 0
CMPIN 0
CMPOUT 0
BATPRES 0
TB_STAT 0
BATSRC 0
BATDRV 0
SRN 0
SRP 0
ILIM 0
GND 0
LODRV 0
REGN 2 drops to 0
BOOT 0
HIDRV 0
PHASE 0
VCC 19.6

[mon2]

REGN 2 drops to 0

Remove all power. Measure the resistance to ground of REGN. Checking if there is a fault here. There is a cap on this rail and if required, flux and remove it. Then check if the resistance is higher than you originally measure. This is a LDO rail that will take the ~19v from the power adapter and buck regulate it to 6 volts.

[DavidRM]

I have replaced DCin MOSFETs with the initial ones (one with source and drain sorted and the other seems ok). Then REGN value is 6.8, ACDRV is 19.8. Also PQ23 has been replaced with a bad mosfet. I think that I am going to buy new ones to repeat all the measures properly.

[DavidRM]

Also i have checked that +VCC_CORE is shorted to GND, it is means that the CPU is dead? Resistance is 4.5 ohm

[mon2]

Wait on other comments but no, the CPU may be ok at this value. If under 1 ohm, then yes, it is shorted. Low voltage rails operate with a low resistance on the devices.

[DavidRM]

Thanks it was a check to see it was worth to continue or not.

The reason is that I have placed a MOSFET whose source and drain were shorted in PQ21. Since I was working fine before and I thought that there was no problem. But I have read that there is the risk of feeding the CPU with 19V, burning it.

Apart of that, with that defective MOSFET in PQ21 and a good MOSFET in PQ22 my laptop was able to power on.

However now it does not. Since the topic is related with a laptop that can work like a desktop but it does not charge the battery (or the case in which works as laptop but not recognized AC adapter).

What can cause that the laptop doesn't power on?

I have read that the main cause is a failure in power supply, but is there a were to check if more hardware involved in power on process has been damaged?

Thanks