Dell N7110/Vostro 3750 no power problem

[hazardus]

Hi guys,

I've a Dell vostro 3750 which has no power at all after I shorted the power ic.
I changed the power IC but the KBC was still shorted.
After I changed KBC there was no more short problem but now no power at the FETs.

I changed PQ44 and PQ43 but still nothing.

PQ44

5,6,7,8 pins has 19.5V
1,2,3,4 nothing at all

PQ43

5,6,7,8 pins has 19.5V
1,2,3,4 nothing at all

What a hell could this be?

[hazardus]

Re: Dell N7110/Vostro 3750 no power problem

PU12 measurements

1 - 1,98V
2 - nothing
3 - 4,94V
4 - 4,84V
5 - 0,30V
6 - 19,30V
7 - 4,95V
8, 9 ,10, 11 nothing
12 - 1,20V
13, 14, 15, 16 nothing
17 - 0,14V
18 - nothing
19 and 20 - 4,97V
21, 22, 23 - nothing
24 - 4,46V
25, 26 - nothing
27 - 4,50V
28, 29 ,30 - nothing
31 0,89V
32 4,95V

This is on the new Power control IC.

[hazardus]

Re: Dell N7110/Vostro 3750 no power problem

Anyone?

[hazardus]

Re: Dell N7110/Vostro 3750 no power problem

I don't have battery so I just can try with power supply.
When power supply connected I mausered 12Ohm on PL11 and 6KOhm on PL10.

[hazardus]

Re: Dell N7110/Vostro 3750 no power problem

Question is why I don't have +5V on PIN 15,18 and why I don't have +3.3V on PIN 23,26?

[dspok]

Re: Dell N7110/Vostro 3750 no power problem

It looks like there still shorting problem somewhere, maybe PU12 itself.

[hazardus]

Re: Dell N7110/Vostro 3750 no power problem

Thanks for your reply.

When I changed it first I thought the replacement chip was bad so I changed it to another one(both were new). Same measurements on the second chip too. The chip doesn't get hot and it's just pulling 0.0043A.

[cyberhack]

Re: Dell N7110/Vostro 3750 no power problem

Pin 14 is low +5v_en1

[hazardus]

Re: Dell N7110/Vostro 3750 no power problem

I don't know why I don't have anything on Pin 14.
I checked the schottky diodes and those are fine.
I've 4.40-4.20 around there(PD4,PD5), but after PG48 nothing.
ALW_ON comes from KBC but there is no voltage.

[khaahk]

Re: Dell N7110/Vostro 3750 no power problem

How did you know that KBC was shorted? Why was it shorted? Was there overvoltage at 3.3V? Is there something else shorted at 3.3V?(LAN?) Resistance from 3.3V ALW to GND is how much? PQ42 is ok?
It seems that +5V ALW_2 should turn on 3.3V ALW through ON2 start signal. You have these conditions met but the controller does not start...

[hazardus]

Re: Dell N7110/Vostro 3750 no power problem

I accidentally shorted the RT8206B because I forgot to turn off the PSU and I got a phone call etc. so I accidentally shorted it. PSU showed 5V and 1A so I know something wrong.
That IC was really hot so I changed it. After I changed it I switched the PSU on and it still showed 5V and 1A so there was still short somewhere. I checked the KBC and it got really hot so I changed that too. Now there is no short at least when I switch the PSU on.

I checked PQ42 several times and it looks ok to me but I'm going to change it anyway.
I don't know why was the KBC shorted I believe I shorted the 3.3V line with something.

I've 5V on Pin 7 so +5_ALW_2 is on as you said.
On Pin 27 I measured 4.50V which is way to much if there should be 3.3V.

[khaahk]

Re: Dell N7110/Vostro 3750 no power problem

Who said that it has to be 3.3V on pin 27? There should be logic level high to enable 3.3V on pin 25. 4.5V seems like logical high level to me.