Asus Model G501j , Board N501jw short at AC_BAT_SYS

[TheWizard]

Hey fellow techs. I have a new issue i have been working on for quite some time now while waiting for parts from china to ship.

- Issue started with no power coming into laptop at all. I replaced the DC IN Jack and received 19v.
- Problem then was 19v would only reach to the first power mosfet. Long story short i replaced both the 1st and 2nd power mosfets.
- I currently have the second mosfet off because if i solder it back the charger gets tripped to protect circuit and 19v is not applied.
- I replaced the current sense resistor above this mosfet but no change.
_ Currently i have 0v across the whole PU8102 chip besides a 0.2 read on P_5VSUS_BST_30. I have replaced this but no change.
- I reflowed PU8800. I can provide readings for that chip currently. Just wanted to see if i am on the right track. Anyone else had issues with this board? Seems like Asus just needs to give up lately. Thanks for your time!

[myth77]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

this board had problems with central pin on dc in jack that would short pch and ite chip...Check there first for short.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Myth77,
What pin are you referring to? Schematic shows 2 grounds and 1, dc in and 1 ac. Or are you referring to someplace else?

[myth77]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

pin 3 a/d max power.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Measured A/D Max Power in Continuity and diode mode. No short.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Here is the read out currently for PU8800
Pin 1 = 0v
Pin 2 = 0v
Pin 3 = 19v
Pin 4 = 19v
Pin 5 = 0v
Pin 6 = 2.6v
Pin 7 = 0v
Pin 8 = 0v
Pin 9 = 0v
Pin 10 = 0v
Pin 11 = 0.2v
Pin 12 = 0.3v
Pin 13 = 0.3v
Pin 14 = 0v
Pin 15 = 0v
Pin 16 = 6.0v
Pin 17 = 5.8v
Pin 18 = 0.3v
Pin 19 = 0.3v
Pin 20 = 19.2

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Measured A/D Max Power in Continuity and diode mode. No short.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Measured A/D Max Power in Continuity and diode mode. No short.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Can someone remove #7 and #8 replies. Phone had a moment. I can't delete them. Thanks!

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Here is the schematic or Asus Repair Guide as they state.

[Sephir0th]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

What has this poor device done to you my friend?

So many components replaced... sry but i can't understand that. You have a shorted main power rail (AC_BAT_SYS), which is one of the most simple faults existing. And you have literally written it in the thread title. So with a 99% chance you have either a shorted capacitor or a internal shorted high-side mosfet. Need assistance to clarify?

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Sephiroth,
I received this laptop for free. A friend's nephew tried to replace the DC IN Jack and failed horribly. I bought a new jack and soldered. Then proceeded to run into all these problems on top of the bad DC In jack. Haha. Yes. I would love all the help i can get. Ready to throw this thing haha

[mon2]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

What are the topside markings of PU8800?

From this feedback, we maybe able to locate a similar charger circuit schematic.

Remove all power. Meter in resistance mode.

Check the resistance from the main power rail after the DCin mosfets to each coil on the logic board.

You are checking for a low resistance which will imply that you have a shorted high side mosfet onboard.

This can be deadly to the CPU if on the CPU power rails.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Mon2,
I posted the schematic in the zip above. I will take these readings and report back. Thanks!

[reformatt]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Refer post #11. Good advice.

You have either an passive or active short on your +19V rail. Not familiar with this charge IC, but the first two FET's are there to protect the laptop. Reflowing and replacing components at random can muddy the water.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Here is a picture pointing to pin 5 of the second mosfet. Which is where I first notice the short.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Mon2,
Are you referring to the power inductors? If so, looks like my lowest readings are coming from PL8101 and PL8100. Highest is 8.5 on PL8101 and lowest 1.5 on PL8100

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Reformatt,
I was getting desperate. Not knowing what was tried the previous repair attempts before me. Haha

[reformatt]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Generally, if you're not getting volts past the first two MOSFET's, first thing is you check resistance to ground at the current sense resistor and you troubleshoot from there. Most charger IC's detect the short and remove the drive to protect the laptop.

With any luck, being an ASUS, it's just a shorted cap on the main +19V rail. But can also be a shorted high side MOSFET for the CPU/GPU. Quick check is to measure resistance between the CPU/GPU coils and the current sense resistor for the +19V rail. If you get low ohms, you have a shorted high side FET and your silicon is probably toast.

[TheWizard]

Re: Asus Model G501j , Board N501jw short at AC_BAT_SYS

Reformatt,
Resistance to ground from current sense resistor is 1.5. What is considered low ohms from current sense resistor to CPU/GPU coils? Mon2 is also assisting me. Thank you to you both. I appreciate it. This one has been a headache. Normally i am the first one to open up a device. This one not so much haha