Asus X512DA - AMD Ryzen 5 3500U - No power

[krayz]

I've ordered a new BQ IC. I also measured the voltage to pin 28 with the BQ removed and I get the 19V. Still curious why I'm getting 3.3v on my 19v rail... But we'll see.

[mcplslg123]

10 Ohms resistor blown always leads to charging ic being shorted. Pad2 resistance to GND clearly indicated that charging ic is faulty.

That's why i always suggest to replace the ic whenever any resistor on vin/vcc line is blown. It has blown 'coz excessive current was drawn.
This applies to all pwm ic and charging ic alone.

[krayz]

Hello again. I have replaced the BQ chip and now i have 19v passing the input mosfets😎

However, when I replaced the IC, the laptop still wouldn't start. Then I started poking around the IC with the multimeter to check some values, and found a problem and solution combo ^^.
If i measure the voltage of pin 5 - PC_CHG_ACOK_10 (measuring on test pad that's right next to it), while the laptop is plugged in, it magically boots and charges. If i remove the probes, the laptop stays on, but stops charging. If I dont do this, the laptop does not respond to the power button.

Thanks for the help so far

[pc_okay]

First thing to do is to check resistance between
S-G
S-D
G-D
of the 2 dc in mosfets.
Next thing to check is whether 19V rail is shorted or not.

If these 2 steps fails, then move on to charger ic requirements.

Please Check résistance on mofset (without power)

You can Check ACDET voltage.(With power)
And tell us your ACOK value With power, dont you short two pins when you Check ACOK?

Review your soldier on IC, QFN chip are a pain to soldier if you are not used to.

[pc_okay]

First thing to do is to check resistance between
S-G
S-D
G-D
of the 2 dc in mosfets.
Next thing to check is whether 19V rail is shorted or not.

If these 2 steps fails, then move on to charger ic requirements.

Please Check résistance on mofset (without power) like mcplslg123 earlier.


You can Check ACDET voltage.(With power)
And tell us your ACOK value With power, dont you short two pins when you Check ACOK?

Review your soldier on IC, QFN chip are a pain to soldier if you are not used to.

[krayz]

It really was a pain to solder i have resoldered it (i'm confident it's good enough), yet the same things are happening.

The two DC in mosfets let the 19v as soon as i plug in the charger, so they should be good (but ill measure when i get home). It's just that the laptop is still unresponsive.

Then i measure ACOK - charging and power led come on and the laptop starts.

ACDET with power - 2,6 V
ACOK with power - 1,3 V

Looking at the BQ datasheet, I'm guessing that by measuring it with my multimeter, i am pulling ACOK high ? (don't know what this means though).

[pc_okay]

Ok you progress.
ACDET is fine.
ACOK is problématique, ACOK is an ON/OFF signal you should get 0v or 3V not 1V or 2V or anithing else.
ACOK provide power to your SIO via 3VA (3V always) so without it, you can't have a power on.

Check résistance to ground on ACOK Line, and Check PQ8905A, it may « kill itself » to protect your SIO during the overvoltage when IC charge burnt.
Sending ACOK to the ground.

That's weird your laptiop start when you take your mesurement.
How do you mesure voltage on ACOK? where do you put red and black probes?

[krayz]

There really is something funky going on ACOK line, when measuring resistance, it goes from 0,7kohm and just keeps rising slowly to over 1kohm. It sure doesn't do either/or with 0v and 3v.

When I measure ACOK, i put black to GND and positive to the test pad shown on picture.



How do i check if PQ8905A for proper functioning? according to the boardview it's this: https://fscdn.rohm.com/en/products/d...em6k6t2r-e.pdf

[mon2]

Post the mosfet measurements as requested above. The adapter voltage appearing downstream can be from leaky and defective mosfets.

[krayz]

With resistance mode and the mosfets desoldered:

1.PQ8901 - QM3056M6AC
------------------------
source (pin 1,2,3) to drain (pin 5,6,7,8) - 0 Ohm / 0.L
gate (pin 4) to source (pin 1,2,3) - 0.L
gate (pin 4) to drain (pin 5,6,7,8) - 0.L


2.PQ8902 - P0903BEA
-------------------------
source (pin 1,2,3) to drain (pin 5,6,7,8) - 0 Ohm / 0.L (and 0,5 Mohm if i reverse the probes for some reason )
gate (pin 4) to source (pin 1,2,3) - 0.L
gate (pin 4) to drain (pin 5,6,7,8) - 0.L

[mcplslg123]

Source to Drain resistance is 0 ohms or OL? i'm bit confused with your writing.

[krayz]

0 ohm when mosfet is on, 0L when it is off.

I used this as a guide:
https://electronicsbeliever.com/how-...-is-defective/

[mcplslg123]

Never measure resistance with power attached.

[pc_okay]

0 ohm when mosfet is on, 0L when it is off.

I used this as a guide:
https://electronicsbeliever.com/how-...-is-defective/

Hello,

To check mofset you just have without power to put your:

• red probe on gate, black on source, then check resistance (has to be >= KOHM or OL), then revert probs
• red probe on gate, black on drain, then check resistance (has to be >= KOHM or OL), then revert probs
• red probe on source, black on drain, then check resistance (has to be >= KOHM or OL), then revert probs

At what point on the motherboard did you found ACOK =1,3 V?
Check this mofset too: PQ8905A with pin 1,2 and 9.

[krayz]

Never measure resistance with power attached.

You misunderstood, i measured the mosfets off the board, desoldered. What i meant with on/off is the mosfet itself:
"However, you should take note that when you put the positive of the DMM to the gate and the negative to the source of an NMOS, the MOSFET will turn on. You might mistakenly judge that the MOSFET is defective when you measure drain-to source resistance since the DMM will read 0 ohm. So, to avoid this scenario, ensure to discharge the charge on the gate".

Hello,

To check mofset you just have without power to put your:

red probe on gate, black on source, then check resistance (has to be >= KOHM or OL), then revert probs
red probe on gate, black on drain, then check resistance (has to be >= KOHM or OL), then revert probs
red probe on source, black on drain, then check resistance (has to be >= KOHM or OL), then revert probs

At what point on the motherboard did you found ACOK =1,3 V?
Check this mofset too: PQ8905A with pin 1,2 and 9.

The measurements of the 2 mosfets are like you specified.

ACOK is between 1-1,5v the whole time, even when the laptop is already booted.

I'l check PQ8905A and all the components on that line next.

[mcplslg123]

I know these facts with NMOS. I just guesssed that may be measuring with adapter connected. lot of people does this mistake. Anyway,doesnt apply in your case.

[krayz]

Hello,

To check mofset you just have without power to put your:

• red probe on gate, black on source, then check resistance (has to be >= KOHM or OL), then revert probs
• red probe on gate, black on drain, then check resistance (has to be >= KOHM or OL), then revert probs
• red probe on source, black on drain, then check resistance (has to be >= KOHM or OL), then revert probs

At what point on the motherboard did you found ACOK =1,3 V?
Check this mofset too: PQ8905A with pin 1,2 and 9.

I've measured PQ8905A (N-MOSFET EM6K1GT2R EMT6) as well. Resistance mode, no power. With both probe polarity.

red (1) & black (6)	250 kOhm
red (2) & black (6)	0,5 MOhm
red (1) & black (2)	0.L

black (1) & red (6)	75 kOhm
black (2) & red (6)	0.L
black (1) & red (2)	45 kOhm

[krayz]

As i was checking the components on the line, I discovered something else as well. It would seem I blew off a component when replacing the BQ: PR8912.



I replaced it with a resistor with the value taken from the boardview (100k). Now the ACOK pin gets 6V. The laptop is not turning on though (with just the adapter plugged in). So... don't know if this is progress or regress

[mon2]

Progress. Now the rest of the logic board is receiving the ok signal to power up. Keep testing.

[krayz]

I searched further and found that i have 3VA, but i don't have 3VA_EC, i'm guessing that's why it isn't turning on. Can't find the cause though. Also, isn't 6V for ACOK too high?