Asus n550jv rev 2.1 no power

[Zilicon]

Greetings...
please I need your help in troubleshooting the above PCB, voltage gets to PQ8801 mosfet but the mosfet doesn't open as there was no voltage at the gate. i traced the gate to the IC (PU8801) that was meant to generate the voltage, but 0V at pin 4, I.ve changed the IC but still the same result.

please help, i'm out ideas and i could not lay my hands on the schematics only the boardview is available. suggestions would highly be appreciated.

[mon2]

Re: Asus n550jv rev 2.1 no power

hi. place your meter in resistance mode, turn off / remove all power. Check the resistance to ground on each and every coil. If you see a very low resistance value, then that rail may be a low voltage rail (ie. CPU core voltage of 1v0 or 1v05, etc.) OR could be a rail with a shorted cap. Bad caps are usually the polarized tantalum style that over time, just die and try to take down the owner with them.

Have repaired a number of logic boards with this process.

You can also check for dry solder joints on the COIL(s) and nearby mosfets. Over time, the ROHS solder can become brittle / crusty and causes hairline cracks that fail eventually.

[mcplslg123]

Re: Asus n550jv rev 2.1 no power

DC-in mosfets are not shorted?? Most common problem in asus is one of the two dc-in mosfet gets shorted. So do check that first.

[Zilicon]

Re: Asus n550jv rev 2.1 no power

DC-in mosfets are not shorted?? Most common problem in asus is one of the two dc-in mosfet gets shorted. So do check that first.

not shorted at all, I even changed both N-channel FETs but still the same

[Zilicon]

Re: Asus n550jv rev 2.1 no power

hi. place your meter in resistance mode, turn off / remove all power. Check the resistance to ground on each and every coil. If you see a very low resistance value, then that rail may be a low voltage rail (ie. CPU core voltage of 1v0 or 1v05, etc.) OR could be a rail with a shorted cap. Bad caps are usually the polarized tantalum style that over time, just die and try to take down the owner with them.

Have repaired a number of logic boards with this process.

You can also check for dry solder joints on the COIL(s) and nearby mosfets. Over time, the ROHS solder can become brittle / crusty and causes hairline cracks that fail eventually.

these are the readings at the coils:

PL8801 90k
PL8701 0k
PL8003 0k
PL8002 0k
PL8502 0k
PL8501 0k
PL8200 0k
PL8301 0.6k
PL8100 14.4k
PL8101 14.4k
L3901 29k
L3901 29k

please what do you think?

plus i see no sign of short on the board

[myth77]

Re: Asus n550jv rev 2.1 no power

Are those readings ih Kohm for all coils? You can not read in Kohm many of these Coils because they have much lower resistence to the ground...some even few ohms.
Use your multimeter in ohms for that that you measure 0k and post back results.

[mcplslg123]

Re: Asus n550jv rev 2.1 no power

post PU8801 pin voltages here.

[Zilicon]

Re: Asus n550jv rev 2.1 no power

Are those readings ih Kohm for all coils? You can not read in Kohm many of these Coils because they have much lower resistence to the ground...some even few ohms.
Use your multimeter in ohms for that that you measure 0k and post back results.

yes there were taken in Kohms.

ok i will update you ASAP

[Zilicon]

Re: Asus n550jv rev 2.1 no power

post PU8801 pin voltages here.

ok thanks.

i will do that ASAP

[Zilicon]

Re: Asus n550jv rev 2.1 no power

ok thanks.

i will do that ASAP

the PU8801 voltage pin

1 0.7v
2 0.7v
3 0v
4 0v
5 0v
6 2.5v
7 0v
8 0v
9 0v
10 0.1v
11 0v
12 1.1v
13 1.1v
14 GND
15 0v
16 6v
17 5.8v
18 1.1v
19 1.1v
20 18.8v

[Zilicon]

Re: Asus n550jv rev 2.1 no power

yes there were taken in Kohms.

ok i will update you ASAP

PL8801 327k (it appears i made mistake in the previous reading)


for the low resistance reading:

PL8701 77.6ohms
PL8003 19.8ohms
PL8002 19.8ohms
PL8001 19.8ohms
PL8501 8ohms
PL8502 80hms
PL8200 76.6ohms

every other coils remain the same, they read in Kilo ohms

[Zilicon]

Asus n550jv rev 2.1 not turning on

Hello Friends,

please I need your help in troubleshooting the above PCB, voltage gets to PQ8801 mosfet but the mosfet doesn't open as there was no voltage at the gate. i traced the gate to the IC (PU8801) that was meant to generate the voltage, but 0V at pin 4, I.ve changed the IC but still the same result.

please help, i'm out ideas and i could not lay my hands on the schematics only the boardview is available. suggestions would highly be appreciated.

PU8801 pin voltage

1 0.7v
2 0.7v
3 0v
4 0v
5 0v
6 2.5v
7 0v
8 0v
9 0v
10 0.1v
11 0v
12 1.1v
13 1.1v
14 GND
15 0v
16 6v
17 5.8v
18 1.1v
19 1.1v
20 18.8v

[questore]

Re: Asus n550jv rev 2.1 not turning on

Test the following points of sequence and write down voltages:
(your pin nr 5 is 0v means some default voltage rails is probably missing (one of 3v 5v etc))

1A +3VA -
1B +5VA -
2 PS_ON -
3 +3VA_EC -
4 EC_RST -
5 3VA_DSW_ON -
6 3VA_DSW_PWGD -
7 DPWROK_EC -
8 ME_AC_PRESENT -
9 PCH_SLPSUS# -
10 5VSUS_ON -
11 3VSUS_ON -
12 5VSUS_PWRGD -
13 +3VSUS_PWRGD -
14 PM_RSMRST# -
15 PCH_SUSACK# -
16 ME_SuspwrDnAck -
17 PWR_SW# -
18 PM_PWRBTN# -
19 PM_SUSC# -
20 PM_SUSB# -
21 SLP_A# -
22 SUSC_EC# -
23 SUSB_EC# -
24 1.35V_PWRGD -
25 +1.05VS_PWRGD -
26 P_1.5VS_PWRGD -
27 ALL_SYSTEM_PWRGD -
28 VRM_PWRGD -
29 PM_PWROK -
30 H_DRAM_PWRGD -
31 DRAMPWROK -
32 H_CPUPWRGD -
33 PM_SYSPWROK -
34 BUF_PLT_RST# -
35 NVDD -

[questore]

Re: Asus n550jv rev 2.1 not turning on

Test the following points of sequence and write down voltages:
(your pin nr 5 is 0v means some default voltage rails is probably missing (one of 3v 5v etc))

1A +3VA -
1B +5VA -
2 PS_ON -
3 +3VA_EC -
...

Forget about all that.

Pin #5 is "ACOK" signal:
AC adapter detection open drain output. It is pulled HIGH to external pull-up supply rail by external pull-up resistor when
voltage on ACDET pin is between 2.4V and 3.15V, and voltage on VCC is above UVLO and voltage on VCC pin is
275mV above voltage on SRN pin, indicating a valid adapter is present to start charge. If any one of the above
conditions can not meet, it is pulled LOW to GND by internal MOSFET. Connect a 10kΩ pull up resistor from ACOK to
the pull-up supply rail

I think since your ACDET és 2.4< 2.5v <3,15 and VCC is close enough to 19V
you should replace the charger chip.

Question: Are you sure pin #11 BATDRV is 0v? Resistance on that pin? Is your battery disconnected?

[Zilicon]

Re: Asus n550jv rev 2.1 not turning on

THANK you so very much, I changed the chip again and it worked. thank you!

the previous chips must have been bad because, i got them from donor boards.

[Zilicon]

Re: Asus n550jv rev 2.1 no power

thank you guys for your help, the board is working now. I changed the chip again, the previous chips must have been bad because i got them from donor boards.

Thanks again and again and again

[questore]

Re: Asus n550jv rev 2.1 no power

thank you guys for your help, the board is working now. I changed the chip again, the previous chips must have been bad because i got them from donor boards.

Thanks again and again and again

Glad that it worked!