Acer Aspire 8951G, power on and immediately turns off (Main DA0ZYGMB8E0 REV E )

Good morning friends of the forum. This laptop enters me with the defect that by giving the power on, the power on led turns on but turns off immediately. Opening it, no traces of oxide. I tried another cpu, reprogramming eeprom bios and eeprom EC but nothing. I find the Always voltages on the PL16 and PL17 coils and are ok. I have noticed a low resistance in the PL9 and PL8 coils (1.50ohm)
I also checked the voltage on the PU1 charger
pin 1 0v
pin 2 3,91v
pin 3 3,20v
pin 4 0v
pin 5 0v
pin 6 0v
pin 7 0v
pin 8 0v
pin 9 3,35v
pin 10 3,35v
pin 11 3,36v
pin 12 0v
pin 13 3,32v
pin 14 0v
pin 15 1,22 and slowly down
pin 16 1,22 and slowly down
pin 17 1,22 and slowly down
pin 18 1,22 and slowly down
pin 19 0v
pin 20 0v
pin 21 5,10v
pin 22 18,55v
pin 23 1,34v
pin 24 1,34v
pin 25 4,80v
pin 26 5,09v
pin 27 19v
pin 28 19v

Hello!

Measure the voltages to ground on all coils for a short time, when the machine is turned on. You will need to turn on the machine multiple times to measure all of the voltages.

robgerr ha scritto:I have noticed a low resistance in the PL9 and PL8 coils (1.50ohm)

Yes, this resistance seems a bit too low. The GPU is probably damaged.

Measure the voltages to ground on all coils for a short time, when the machine is turned on. You will need to turn on the machine multiple times to measure all of the voltages.

PL1 0,90V
PL7 1,51V
PL10 0V
PL11 0V
PL12 0V
PL13 0V
PL14 1,06V
PL15 1,82V
PL16 3,33V
PL17 5,08V
PL18 0V

Measure the resistances to ground on all coils with 0V.

Measure the voltages to ground on pin 10, 11, 13, 24 of chip PU10 for a short time, when the machine is turned on.

PL10 21 OHM
PL11 13 OHM
PL12 13 OHM
PL18 38 KOHM
I forgot to write that PL8 and PL9 remain at 0v during power on

Measure the voltages to ground on pin 10, 11, 13, 24 of chip PU10 for a short time, when the machine is turned on

PU10:
pin 10 3,33v
pin 11 3,35v
pin 13 0,90v after power on go to 1,15 and drop to 0,85 after mainboard shutdown
pin 24 0,75V

Measure the voltages to ground on all pins of transistors PQ63, PQ72 when the machine is turned off.

Measure the voltages to ground on pins 1, 4 of transistors PQ19, PQ73, PQ75 for a short time, when the machine is turned on.
Measure the voltages to ground on pins 1, 2 of transistors PQ9, PQ54 for a short time, when the machine is turned on.

Transistors PQ9, PQ54, PQ63, PQ72 pin count:

pq63:
pin 1 0v
pin 2 0v
pin 3 3,37v
PQ72:
pin 1 0v
pin 2 0v
pin 3 5,08v

PQ73
pin 1 5,08v
pin 4 11,70v
PQ75
pin 1 3,37v
pin 4 11,70v

PQ9:
pin 1 1,51V
pin 2 11,68v

PQ54
pin 1 0v
pin 2 0v

How about the transistor PQ19?
Measure the voltages to ground on pins 1, 2 of transistors PQ63, PQ72 for a short time, when the machine is turned on.

Measure the resistance to ground on pin 1 of transistor PQ54.

Measure the voltages on pins 3, 5, 6 of CN15.
Measure the voltages on pin 2 of the CN15 in the following cases:
at power off
with pressed power on
to power on.

How about the transistor PQ19?

Sorry, missed,
PQ19
pin 1 1,06v
pin 4 11,71v

Measure the voltages to ground on pins 1, 2 of transistors PQ63, PQ72 for a short time, when the machine is turned on.

PQ63
pin 1 3,37v
pin 2 11,86v
PQ72:
pin 1 5,08v
pin 2 11,86v

Measure the resistance to ground on pin 1 of transistor PQ54.

98Kohm

Measure the voltages on pins 3, 5, 6 of CN15.
Measure the voltages on pin 2 of the CN15 in the following cases:
at power off
with pressed power on
to power on.

Hi machine
CN15 only pad, no connector:
pin 3 0v
pin 5 0v
pin 6 0v
Pin 2 measure:
popwer off 3,32v, when press power button drop to 0,44v, after release power button go back to 3,32v

Did you take the measurements on CN15 after pressing the power button?
If the answer is yes:
Replace the bios and remember to save the old one.
If the voltages on CN15 do not appear, replace the KBC.

The bios has been reprogrammed but has not given positive results.
on CN15 I redid the measurements but I tried with the "CREST" function of my "brymen" multimeter.
Practically this function detects the maximum peak voltages very quickly.
I write the voltages on cn15 with the crest function active:
PIN 3 1,23V
PIN 5 1,39V
PIN 6 2,41V
If I try without the crest function of my brymen multimentro I always see 0V
If I had to replace the kbc, the one mounted on the main board is NPCE791LA0DX, my spare that I have instead NPCE795LA0DX.
Can it work?

The voltages on CN15, after pressing the start button, must remain stable at 3v.

Measure the voltages to ground on pins 1, 3, 4, 6, 10, 11, 14 of chip PU9 for a short time, when the machine is turned on.

Measure the voltages to ground on pins 1, 3, 4, 6, 10, 11, 14 of chip PU9 for a short time, when the machine is turned on.

PIN 1 2,02V
PIN 3 0V
PIN 4 5V
PIN 6 0V
PIN 10 5,08V
PIN 11 0V
PIN 14 4,58v

Measure the voltages on pins 5, 10, 14, 15, 16, 22, 23, 24 of PU10.

Measure the voltages on pins 5, 10, 14, 15, 16, 22, 23, 24 of PU10

PIN 5 0,75v
PIN 10 3,33V
PIN 14 5,07V
PIN 15 5,08V
PIN 16 4,74V
PIN 22 6,2V
PIN 23 1,50V
PIN 24 0,75V
*The measurements were made during the power on*

Check PR148=1.3K, PR250=2K
Check that PC125 is not shorted.
On pin 1 of PU9 there must be 3v.

Check PR148=1.3K, PR250=2K
Check that PC125 is not shorted

All component's checked and are ok

Replace PU9, PQ76.