No power on G512LI

[vrasp]

Hi,

I received an asus laptop G512LI that doesn't power on. Apparently it suddenly turned off. There was no spill or anything like that.

I have some/little experience fixing boards. I have not been able to find a schematic and boardview for this board. Are there other motherboards that are similar for which there are available?

So far I've determined that the adapter is providing 20.2V at J6001 and there is 0.12V on pins 6-8 and 0v on pins 4-5 of PJ6001 (the battery). The badcaps guide says to "check the voltage after the 2nd DC-in MOSFET and after the current sensing resistor for AC adapter power input.". I m not sure how to find these without a proper schematic and boardview.

How can I easily determine whether it's the battery or something on the board?

Thank you for your help,

Vrasp

[mcplslg123]

Re: No power on G512LI

DC-in mosfets can be easily located and usually they are near dc-in jack. There will be two of them . Try locating them and then measure voltage on Pin1-4-8 of these mosfets. Else post a clear pic of your motherboard-we'll help you locate them.

[vrasp]

Re: No power on G512LI

Here are the front and back pictures of the DC jack and battery connectors. I put green dots where I think the MOSFETs are for the DC_JACK. Is that correct?

[mon2]

Re: No power on G512LI

Yes. Download the datasheet for each mosfet to review the pinout. Then without power to the board, measure the resistance across the pins.

Source & drain
Source & gate
Gate & drain

Post each measurement.

[SMDFlea]

Re: No power on G512LI

Posted the schematic earlier today -> https://www.badcaps.net/forum/showthread.php?t=119245 .

.

[vrasp]

Re: No power on G512LI

Yes. Download the datasheet for each mosfet to review the pinout. Then without power to the board, measure the resistance across the pins.

Source & drain
Source & gate
Gate & drain

Post each measurement.

I m getting "infinite" resistance between all of them.

[mon2]

Re: No power on G512LI

Good. Review the schematic linked above and then measure the following points of interest on the charger IC:

REGN
ACDRV
ACDET
ACOK
CMSRC
ACP
ACN

[vrasp]

Re: No power on G512LI

I finally got around to it. With the charger and battery plugged in I got:

REGN -> 5.95 V
ACDRV -> 0 V
ACDET -> 0 V
ACOK -> 1.69 V
CMSRC -> 0 V
ACP -> 0 V
ACN -> 0 V

Thanks!

[mon2]

Re: No power on G512LI

ACDET should not be 0 volts when the power adapter is plugged in.

Locate pr8904 that is use for the ACDET circuit.

Measure the voltage to ground on each side of this resistor.

Remove all power and with meter in resistance mode, measure the resistance across pr8904.

Post each measurement.

[vrasp]

Re: No power on G512LI

My bad the writings in the schematic were shifted and so were my readings. It goes:

REGN -> 5.95 V
ACDRV -> 0 V
ACDET -> 1.69 V
ACOK -> 0 V
CMSRC -> 0 V
ACP -> 0 V
ACN -> 0 V

[mon2]

Re: No power on G512LI

ACDET is still too low of a voltage for a good adapter voltage.

This pin should be 2v4 or higher and only then the charger IC will consider the adapter voltage to be suitable to power the logic board and charge the battery.

See here:

https://ohmslawcalculator.com/voltag...der-calculator

Input:

18volts. ; Minimum expected adapter voltage is 17v8
127000 ohms ; r1 = pr8904
20000 ohms ; r2 = pr8905

And then press calculate. Your true voltage on the logic board should match or exceed this calculator voltage.

Proceed to review the resistors pr8904 and pr8905 and check each resistor value. Something is wrong here.

[vrasp]

Re: No power on G512LI

I got 75.5 Kilohms for r1 and 18.8 Kilohms for r2. Based on the calculator, that should give me about 4 V. Does that mean the charger IC is shot?

[mon2]

Re: No power on G512LI

See attached.

1) measure the voltage to ground on each side of PR8904.

Post the measurements.

2) Remove all power -> meter in resistance mode.

Measure the resistance to ground at the common junction of PR8904 & PR8905.

3) Yes, the voltage to ground at the common junction should be ~3v5 based on your measured resistor values but it is not so someone is pulling down this line or the resistors are defective.

[Sephir0th]

Re: No power on G512LI

A picture of the ACDET curcuit location would be nice and resistors have to be checked out of circuit. Don't miss there is also a Short protection circuit connected, consisting of PR9024 and PD9002. ACDET voltage is supposed to be 2.6 Volts here

[vrasp]

Re: No power on G512LI

I got

20.2 V on pin 1 of PR8904
1.69 V on pin 2 of PR8904

Resistance to ground at the common junction of PR8904 & PR8905 is 18.8 Kilohms

[vrasp]

Re: No power on G512LI

On PD9002 I got

Pin 1: 1.09 V
Pin 2: 0 V
Pin 3: 0.6 V

PR9024 resistance to ground

Pin 1: 78 KiloOhms
Pin 2: 91 KiloOhms

PR9024 voltage

Pin 1: 20.2 V
Pin 2: 0.6 V

[mon2]

Re: No power on G512LI

Resistance of pr8905 is matching the schematic values.

Pr8904 resistance is not.

Carefully flux and remove pr8904 resistor. Do not lose this part. After it is removed, measure the resistance of pr8904 while it is on your work table.

Suspecting that pr8904 will not match the schematic value.

[vrasp]

Re: No power on G512LI

I fluxed and carefully removed, measured, and resoldered PR8904, PR8905, and PR9024.

They all match the resistance values on the schematic.

[mon2]

Re: No power on G512LI

Suggest to replace the charger IC. Buy spares. Also recommend to purchase the surrounding mosfets linked to the charger IC. They will not be expensive.

When you do flux and carefully remove the charger IC -> check if the voltage at the resistor based voltage divider returns to the proper range without this IC.

[vrasp]

Re: No power on G512LI

I removed the IC and checked the voltage. It's still 1.69 V at the divider. I'm gonna place the order you mentioned.

What else could be lowering the voltage on that line? It is worth removing the capacitor and checking the voltage again?

Thanks for the help!