Asus GL503VD Not charging or powering on

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

hi,

I got the order and replaced the 2 TPCA 8059-H mosfets. Now I'm not getting 0.4v anymore but 19v. My laptop is still refusing to power on and i noticed the volage fluctuates between 19.60-19.85v.

[mon2]

Re: Asus GL503VD Not charging or powering on

Carefully measure the voltage to ground of each pin on the BQ24780S charger IC with the power adapter connected.

Post each measurement and the pin numbers.

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

I heard a click sound after leaving the power adapter connected and the voltage dropped to 0.4v again. a shorted component is killing the mosfet I think.

[mon2]

Re: Asus GL503VD Not charging or powering on

Remove all power. Meter in resistance mode. Check the resistance to ground of each inductor. Checking for low resistance readings.

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

Where should i check exactly?

[mon2]

Re: Asus GL503VD Not charging or powering on

Locate the large square grey inductors. There will be 2 tabs on the component; one on each side. These are the coils (inductors) and are used for the local switching power supply rail.

Respectively, each coil has local capacitors and then the final target load.

We need to check the resistance to ground of this coil to understand if there is a possible shorted component on that rail.

Start with the mosfets that you recently replaced -> one meter probe on the source pins (1-2-3 = pick one as they are shorted on the mosfet); other meter probe to ground.

What is the resistance? Make a list and post it here.

Repeat with checking the gate pin # 4; then drain pins (5-6-7-8).

Repeat for the next mosfet that was replaced.

Then hunt down all coils on the board and repeat this testing.

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

Okay i will check, does it matter if i use the ground pin from the dc jack or a other ground point?

[mon2]

Re: Asus GL503VD Not charging or powering on

Ground can be any known good ground. It can be the metal shields or the backside of a local capacitor.

To confirm the ground, place the meter in the lowest resistance scale. One meter probe to the ground of your DC power adapter connector; other meter probe to a capacitor pin.

If the resistance is really low like 0.3 ohms or less, then the ground is the same and you can use either pin.

Another method is to use diode mode scale on your meter. Short the meter probe and the meter should tone beep.

Now repeat the above testing with 2 points of interest. If the meter tone beeps, the trace is likely the same ground and is with a low resistance. Resistance method is preferred but tone beep is a quick way to get started to locate a local ground.

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

Okay the ground points are good.

I checked resistance of both mosfets i replaced and i'm getting 0.5 ohms on the drain pins when measuring the mosfet on the left side. The mosfet on the right side gives me 7K ohms on the drain pins. I get the same resistance on the source pins and gate pin from both mosfets. My multimeter was set to 20K when i was measuring

however.. if i set 200k on my multimeter i get 39.2k ohms as reading on the pins where i was getting 7k ohms on. Im not sure if that is normal ?

I also checked the resistance from the inductor close to the battery charger ic and im getting 7.51k ohms when multimeter is set to 20k, when i set 200k on my multimeter i get 32.7k ohms as reading.

[mon2]

Re: Asus GL503VD Not charging or powering on

That is a very low resistance to ground.

Can you identify if this mosfet is PQ21 or PQ22 ?

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

I checked and i believe that the mosfet with low reading is the PQ22.

[Vesko356]

Re: Asus GL503VD Not charging or powering on

The short is gone after desoldering it. Both mosfets are the TPCA 8059-H so i will replace them both.

And most probably you're wrong with your conclusion about the fault.

You see? What did I told you?

Obviously you have a shorted main power line...

That is a very low resistance to ground.

Can you identify if this mosfet is PQ21 or PQ22 ?

Yes it is, I don't have a schematic for this board, but according to the image these are first two input fets.

@Jasonexe:

Exactly as I told you, 0.6 Ohms is a dead short. Now you must find what is shorting your main power line.

.

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

You see? What did I told you?


Yes it is, I don't have a schematic for this board, but according to the image these are first two input fets.

@Jasonexe:



.

What could i do to find the short? before i tried injecting 1v to see if anything gets hot but nothing was heating up.

[Vesko356]

Re: Asus GL503VD Not charging or powering on

What could i do to find the short? before i tried injecting 1v to see if anything gets hot but nothing was heating up.

Try the same again - use a thermal camera to find the warm area.

.

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

Try the same again - use a thermal camera to find the warm area.

.

I don't have a thermal camera. I got isopropyl alcohol, i could give that a try.

[mon2]

Re: Asus GL503VD Not charging or powering on

Have not gone through this whole thread but was there not a link to the schematic? Have the schematic from a locked paid service so can take screen grabs only of select areas.

Remove all power. Meter in resistance mode.

One meter probe to the drain pins showing the low resistance to ground. Other meter probe to any inductor on the board. If the resistance is not 0.6 ohms, check another inductor. Continue to check all inductors on the logic board.

We are checking to see if you have a high side mosfet that may be leaky.

Also, remove this mosfet and check if the same drain pins are with the low resistance to ground on the pcb.

You can check the removed mosfet for the short condition but likely is now defective.

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

Have not gone through this whole thread but was there not a link to the schematic? Have the schematic from a locked paid service so can take screen grabs only of select areas.

Remove all power. Meter in resistance mode.

One meter probe to the drain pins showing the low resistance to ground. Other meter probe to any inductor on the board. If the resistance is not 0.6 ohms, check another inductor. Continue to check all inductors on the logic board.

We are checking to see if you have a high side mosfet that may be leaky.

Also, remove this mosfet and check if the same drain pins are with the low resistance to ground on the pcb.

You can check the removed mosfet for the short condition but likely is now defective.

i measured resistance from all inductors with one probe on the drain pins that had low resistance and all the inductors had a higher resistance then 0.6 ohms. I removed the mosfet and i'm still getting the same resistance from drain to ground.

[Vesko356]

Re: Asus GL503VD Not charging or powering on

What's the current draw if you inject 1V/2A at the shorted line now?
Do it at least for several minutes to see if anything heats up.

.

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

What's the current draw if you inject 1V/2A at the shorted line now?
Do it at least for several minutes to see if anything heats up.

.

it's been 4 minutes now and i still don't feel anything getting hot. It's drawing 0.583A

[Jasonexe]

Re: Asus GL503VD Not charging or powering on

if i measure the voltage with my multimeter while injecting, it gives me 48 millivolts