Sony Vaio PCG-71211M starts and shuts off after 3 seconds and so on continuously.

This laptop starts and shut off after 3 seconds and restarts continuously.

Motherboard code is
M960_MP_MB
8Layer MBX-224

I check

PL5= 70 ohm
PL7= 6 ohm
PL8= 19 Kohm
PL18= 54 ohm
PL6= 14 Kohm

I check

PL5= 70 ohm
PL7= 6 ohm
PL8= 19 Kohm
PL18= 54 ohm
PL6= 14 Kohm

Now please measure the voltages on those inductors (in reference to ground) before and after switching-on.

Ok
All voltages just plugging power supply in= 0V

Pushing power button all voltages stay on for a while less than 1 second.

PL6= 1,5V
PL18= 1V
PL7= 1V
PL8= 0,20V
PL5= 0,20V

valieromarco napisał(a):I check

PL5= 70 ohm
PL7= 6 ohm
PL8= 19 Kohm
PL18= 54 ohm
PL6= 14 Kohm

I think that you have a wrong measure in PL8 and PL5, should be the same.



Please repeat this measure on those inductors

I know, but pc shuts down immediately, maybe it cannot reach right voltage, rebooting continuously, but value is 0,20V/0,25V

Measure the voltages on pins 13, 14, 31, 15, 26, 7, 18, 17, 3, 21, 30 of PU28

Testing PU28 when I put red cap on pin 13 notebook boot with logo VAIO, motherboard was rebooting continuously of course.
Unplugging power and plugging it again when I push power button, problem returns again.

-- 14 May 2014 --

Maybe with red cap I shorted pin 13 and 14 or 12 and 13, now when I touch with cap near pin 13 motherboard starts, but no video now, so I measured all PL and only PL 5 and PL 8 are without voltage.

Check welding of PU28.
Make the required voltages of PU28

All pin measured with power supply plugged 0V

When it starts

13 3,3V
14 0V
31 3,3V
15 0V
26 5V
7 5V
18 3,3V
17 0V
3 4V
21 6V
30 5,8V

PL5= 70 ohm
PL8= 19 Kohm

Inductors connese together can not have different values​​.
PL8 too high.
Measure the voltage on pin 16 of PU28.
Measured with the oscilloscope, the signals on the gate Pq40, PG36, PQ38, PQ37

I checked PL5 and PL8 again, 70 ohm both.

-- 27 May 2014 --

Now when I push button it try 3/4 then hdd starts green led stay on but not video, I will try to reflash bios.

On PL5 and PL8 voltage is present?

Yes 1V

On external monitor works?
Measure the voltages on pins 1, 2, 3 U17
voltages pins 3, 4, 5 of CN5
voltage pin 40 CN13
BGA reflow (LP-M2 AMD Madison Park XT-M2)

Before checking those voltages, if flashing bios did not resolve I think problem is GPU, but not reballing replacing GPU because when PC starts there is no HDD activity, I try to reflow GPU, but nothing is changed

After replacing GPU nothing is changed