Asus K53SD restart,no picture

[ziko07]

Hi, I have this laptop when insert charger battery charging is on andcwhen press ON button,power led lights 1-2 sec and goes off. I opened and reset bios,after that power ked is on and 2,3 more leds is on but after 6sec restart and loops constantly same (only charger insert,without press power button). As I see no more battery charging led is on. It draws 370-450mA. All power present, on cpu cire 0.6v only missing power is gfx core.
any help?
Pcb is rev 6.0, I put bios 5,1 and after that found here 6.0 but no changes on laptop behaviour
Tnx

[mon2]

What is the history? Any liquid damage? Just died one day? Often, some shorted capacitor is causing an excessive current draw and that local power rail is shutting off leading to the observation if the fault is not from other factors.

Remove all power. Meter in resistance mode. Measure the resistance to ground at each inductor. Each inductor is a local buck regulator and there may be a fault at one of these downstream regulators. The GFX core will probably not be enabled till it is required using extensive graphics or till after the device driver loads.

Be sure the power supply is ample to support this laptop.

[ziko07]

No liquid damage, just died, here is image with voltage and resistance on power coils. 5v alw and 3v3 have resistance more then 5k and both power draive ~90mA when bring external desired voltage on coils

[ziko07]

i found what going mad hot , its IC ISL95831 PWM controller for CPU core, but cpu core voltage 0.6v present, or maybe its low voltage for cpu??

[ziko07]

There was short on gate of both FETs, when removed IC short gone, must find that IC to test, hope not processor dead.
0.6V that shows on cpu coils actually not have PWM on one side of coil at all. Now I lift one side of coil, resistance from mcu core VDD to GND is only 5R8, not know is it normal or also processor gone

Tnx

[ziko07]

I got aliexpress ics, tried 2 no joy, even power ok pin thru series 10k resistor has 3v3 on one side only when install IC
probably fake chips, I also desoldered coils to mcu...
see age "new" ic from package opened

[mon2]

Is that a bottom side view of a 'new' IC from Aliexpress? I would complain.

At the very least, flux the backside and then use desoldering braid to suck up the solder shorts so that each contact is visible. Watch the heat used to do the job so that the pins are not lifted off the component. You are trying to flatten each pad and also remove the massive amounts of shorts along the contacts. Then flux it again and apply into your PCB for resoldering before testing.

Be aware of the pin # 1 markings on the IC for the proper alignment.

[ziko07]

Only one from 5 was like this, other looks ok but when insert on pcb I lost 3v3 on VRM,_PWRGD at pin 8 on IC. It comes on 10k resistor, one side has 3v3, other side that goes to pin 8 on IC is zero voltage

[mon2]

VRM,_PWRGD is open drain. Only if the power rail (VRM) is OK, then this output signal will float.

Then the 10k resistor will pull-up the floating line to 3v3. Since it is @ 0v, this means this power good output is stating the power rail (VRM) is not good.

[ziko07]

VR_ON pin7 on ic is present...
Tnx but think will give up, first problem was no vc core and this ic was hot and make hole in it
power rail (VRM) mean when there will output 0.8v to cpu? Sorry I ask this butvmy primary job is car electronics, this is hobby more