ASUS TUF FX516PM - no power

[Gigabyte_PL]

mon2 I'm counting on your help 🙄

[mon2]

The pull-up voltage for the smbus lines is linked to a local load switch from uPi with part number uP9030. This load switch requires the main power rail which is absent so back to the basics. Trace the dcin mosfets.

remove all power. Meter in resistance mode.

check resistance of:

source & drain
source & gate
gate & drain

post each measurement. Repeat for the 2nd dcin mosfet.

[Gigabyte_PL]

tHello mon2 ,

I again test it:
First mosfet:
source & drain - 5,18M ohm
source & gate - 3,17M ohm
gate & drain - 4,83M ohm

Second mosfet:
source & drain - 5,28M ohm
source & gate - 4,70M ohm
gate & drain - 7M ohm

Additionally, last time I replaced the first and second mosfet, but there was no change. I tested the original mosfet and all the resistance and test diode were fine.
I checked motherboard with a thermal imaging camera and only one element that lights up is PR9024. I checked its resistance in circuit and it is 13.7K ohm (that is, as much as in diagram).

[mon2]

Flux and carefully remove PR8918 = ~4k ohm resistor which is in series with the ACDRV pin on the charger IC. Do not lose this part.

Then power up and check the voltage to ground of the ACDRV pin # 4. Measure it carefully. What is the voltage to ground now?

[Gigabyte_PL]

After remove PR8918
ACDRV - 0,17V #4
Source and gate on first mosfet - 0,07V

I checked resistance of PC8916 and its value is 4.65 M ohms (measurement in circuit)

[mon2]

Consider to replace the charger ic. Be sure the replacement is the same as the original. Purchase a few spares.

[Gigabyte_PL]

Ok, I will buy new charger IC. I belivie BQ24800RUYT it's same that BQ24800RUYR? I checked and I saw different information in the packaging. Can you confirm ? Thanks.

[mon2]

Yes, they are the same. They only vary in the shipped quantity on a reel. That is 250pcs vs 3000pcs.

we use suhms on AliExpress but you should be able to receive as a free sample from the ti.com website.

[Gigabyte_PL]

Hi,
I bought a BQ24 yesterday and replaced it now. The same situation - on the measuring resistor 4V.
Maybe new chip is damaged...

[mon2]

Confirm the soldering.

carefully measure on this charger ic - each pin's voltage to ground. Post each measurement.

[Gigabyte_PL]

After soldering, I checked all pins and everything looks good.

I checked again by measuring BQ24:
CHG_ACN - 4,15v
CHG_ACP - 4,15V
CHG_CMSRC - 0,7v UP T0 1,10V
CHG_ACDRV - 0,85V UP TO 1,4V
CHG_ACOK - 0,002V UP TO 0,05V
CHG_ACDET - 2,64V
CHG_IADP - 0,03V
CHG_SDA - 0,57V UP TP 0,9V
CHG_SCL - 0,56V UP TO 0,9V
CHG_ILIM - 0,02V UP TO 0,14V
CHG_LG - 0V
CHG_REGN - 6V
CHG_HG - 0,22V
CHG_LX - 0,22V
CHG_VCC - 19V


when I turn on power supply from the service power supply, consumption of 0.08A appears every now and then and drops to 0 and so on.

[mon2]

These measurements were with both the battery and power adapter attached?

[Gigabyte_PL]

I connected service power supply without a battery. I don't have the original power supply

[mon2]

Trace these pins using board view file:

CHG_ACN - 4,15v
CHG_ACP - 4,15V

these signals are after the dcin mosfets which are off yet you have a voltage on each. Be sure the soldering is ok. Best to review the voltage to ground on each of the dcin mosfets again.

source
gate
drain

without the high gate voltage to enable the mosfets, the referenced pins should be at 0 volts since the battery is not connected.

[Gigabyte_PL]

Mosfet #1
source 0,02V up to 0,8V (up and down - it's unstable)
gate 0,02V up to 0,8V (up and down - it's unstable)
drain 19V

Mosfet #2
source 0,02V up to 0,8V (up and down - it's unstable)
gate 0,02V up to 0,8V (up and down - it's unstable)
drain 4,10-4,20V

[mon2]

Can you confirm that the mosfet pins being measured are:

source (1-2-3) ; any will be ok
gate (4)
drain (5-6-7-8) ; any will be ok

[mon2]

Do confirm that the DCin mosfets you are measuring are located @ PQ8901 and PQ8902. Interested in the voltage to ground of each pin on these parts.

[Gigabyte_PL]

Yes, I confirm.

Check attached files.

[mon2]

In tracing the current sense resistor appears to be from the drain pins on PQ8902.

Can you confirm the following measurements?

CHG_ACN - 4,15v
CHG_ACP - 4,15V

[Gigabyte_PL]

Please check attached files.