Dell Inspiron 17R 3721 (LA-9102P) - No power on

Hi I have a Dell Inspiron 17R 3721 (LA-9102P) It is not powering on plugged in it draws 0.01A and after press power button it drws 0.02A for around 20seconds then goes off, power LED is on whilst this happens.
19V line is ok, i have 3VALW, 5VALW, VREG3 and VREG5 are all present.

Power on/off signal drops low when button is pressed measured on KBC and KBC is getting power. I think that PCH may not be getting power? There is no PM_SLP_S signals coming from the PCH (UH1) and after inspecting the area the capacitor on top of PCH chip is reading ~0.7v after power button pressed.

If i am not mistaking PCH requires +3VS, and this is generated by QZ7 which is outputing 0.7v on pin 1,2,3 and 0V on gate pin 4. I do not know where to go from here and would appreciate your assistance. below are the measurements i have recorded. schematic is available on this site.

Thank you

PU200
-----
8 = 3.3v
17 = 5.1v

PL200 = 3.3V
PL201 = 5.1V


KBC = KB9012QF before / after pwr button

6 = PM SLP S3 - 0v / 0v
9 = 3VALW - 3.3v / 3.3v
24 = PM SLP S5 - 0v / 0v
40 = PCH_PWR_EN# - 0v / 0v
100 = EC RSMRST# - 0v / 3.3v
114 = ON/OFF - 3.3v / 0.4v (goes low)
127 = PM SLP S4 - 0v / 400mv

Capacitor on top of UH1 = 0v off plugged in / 0.7v after power button

page 35 of schematic
QZ7 +3VALW to +3VS

pin 1 - 3 = 0v / 0.7v
pin 5 - 8 = 3.3v / 3.3v

Measure the voltages on pins 16, 106, 110, 124 of KBC.

Please note i am not using genuine Dell adapter, i am using probes from power supply to supply power. thank you

16 = PS ID - 0v / ~0.2v
106 = PBTN_OUT# - 0v / 1.9v
110 = ACIN D - 3.27v / 3.27v
124 = +V18R - 1.78v / 1.78v

106 = PBTN_OUT# - 0v / 1.9v

Voltage too low. Measure resistance to mass.

16 = PS ID - 0v / ~0.2v

Voltage too low.
Measure the voltages in the image at the points indicated by a green circle.

here are readings

Measure the resistance to ground on pin 1 of PQ901, PD901.

PQ901, PD901 pin count:

PQ901 = 114k ohms

PD901 = 2.3k ohms

I am not using a genuine Dell adapter, i am using power supply.
so there is no voltage on adapter ID pin, will that not make a difference?

KenM0560 napisał(a):I am not using a genuine Dell adapter, i am using power supply.
so there is no voltage on adapter ID pin, no?

Yes, the "PS_ID" voltage is missing, but it is not caused by the charger. After repairing the identification circuit you will need a genuine Dell adapter to test the laptop.

Check the resistors PR902, PR903. If both are good, remove the diode PD901 from the board and measure the voltage to ground on pin 1 on the place of that diode.

resistor PR902 and PR903 measurements are good.

i removed PD901 from board

Voltage on pin 1 was 97mV. It seemed to be pulsing also, the multimeter kept calculating on/off 97mv.

Reflash the KBC chip. Don't forget to save the old dump.
If the voltage still does not appear on pin 1 of PD901, it is bad KBC chip.

ok i will try find KBC file.

I have SAS programmer, but not keyboard module, is it possible to use the 30pin ribbon cable in the 32pin connector like in attached picture.?

KenM0560 napisał(a):I have SAS programmer, but not keyboard module, is it possible to use the 30pin ribbon cable in the 32pin connector like in attached picture.?

Yes, of course.

I program KBC with file from internet and issue is still the same, no power on. Just 0.02A consumption after press power button.

I did manage to find genuine Dell adapter and with that plugged in the measurements of PS_ID circuit are slightly different than before, see below.

KenM0560 napisał(a):I did manage to find genuine Dell adapter and with that plugged in the measurements of PS_ID circuit are slightly different than before, see below.

These are the correct values.

Does the board respond to pressing on the power button with genuine Dell charger?
Does the battery charges?

With genuine Dell charger and battery plugged in, i get white battery LED.

After power button press, power LED comes on, but no fan spin or sign of powering on.

There must be another issue with the board?

Measure the voltages on all the coils.

here are coil voltges

pwr_button before/after

PL100 = 0.4v / 0.4v
PL200 = 3.3v / 3.3v
PL201 = 5.1v / 5.1v
PL202 = 19v / 19v
PL300 = 0 / 0
PL400 = 0 / 0
PL500 = 0 / 0
PL600 = 0 / 0
PL700 = 0 / 0
PL701 = 0 / 0

Original power supply?
Measure the voltages on all the pins of PU400.
Measure voltage and resistance to ground of PL400.

Yes, orignal power supply

PL400 = 460k ohms
0v / 0v

PU400
1 = 0 / 0
2 = 0 / 0
3 = 0 / 0
4 = 0 / 0
5 = 0 / 0 (enable pin)
6 = 0 / 0
7 = 0.7v / 0.6v
8 = 3.3 / 3.3v
9 = 3.3 / 3.3v
10= 3.3 / 3.3v

Measure the voltages on all the pins of PU300.
Measure voltage and resistance to ground of PL300.