Asus x455l

[mardocdor]

Hello good day! I have this ASUS X455L that wont turn on and even if i plug the power adapter it wont charge and the charging light indicator wont lit... i've done initial troubleshooting i found out that there is smd component marked 43t shorted but when i pull out it was ok, and there is 20 pin smd component beside it marked 5E=3H which im not sure what type of component it is and i suspected it to be shorted since some of its pins tested shorted. by the way can somebody share a schematic to me... thanks

[piernov]

Re: Asus x455l

5E= is Richtek RT8248A, which should be used for the RAM power supply so that's not your issue. Your issue seems to be related to charging circuit, most likely the DC-in MOSFET (there are probably 2 of them near the DC-in connector) which can be shorted or a defective charger IC (around this area too). You could have a shorted B+ line too, you can check that by measuring the resistance to ground after the DC-in MOSFETs.

[mardocdor]

Re: Asus x455l

hi thanks for your quick response... do you have schematic for this model?

[mardocdor]

Re: Asus x455l

5E= is Richtek RT8248A, which should be used for the RAM power supply so that's not your issue. Your issue seems to be related to charging circuit, most likely the DC-in MOSFET (there are probably 2 of them near the DC-in connector) which can be shorted or a defective charger IC (around this area too). You could have a shorted B+ line too, you can check that by measuring the resistance to ground after the DC-in MOSFETs.

i measured the resistance to ground after the DC mosfets it measured 2 ohms, is it normal for this model?

[piernov]

Re: Asus x455l

If you're measuring after the DC-in MOSFET (*not* the CPU ones) then 2 ohms is way too low, you should have at least several kohms. It means the B+ line is shorted. Inject 1V using a lab power supply and check which component gets hot. If the CPU/PCH/GPU don't get hot and nothing else get hot, you can increase the voltage a little.

[mardocdor]

Re: Asus x455l

If you're measuring after the DC-in MOSFET (*not* the CPU ones) then 2 ohms is way too low, you should have at least several kohms. It means the B+ line is shorted. Inject 1V using a lab power supply and check which component gets hot. If the CPU/PCH/GPU don't get hot and nothing else get hot, you can increase the voltage a little.

i did what you advised me to do, i used my lab power supply and increase the voltage and current little by little until it reaches 19V 2A and found out that one of the internal RAM chip is getting significantly hot...

[mardocdor]

Re: Asus x455l




first DC mosfet has 19V input from DC jack but no output so i by pass the 1st mosfet

[mardocdor]

Re: Asus x455l

[mardocdor]

Re: Asus x455l




then the 2nd A5 VNC mosfet output and the 3rd and 4th E4 GUC mosfet near that big coil and PJP8302 tested less than 2 ohms to ground...

[mardocdor]

Re: Asus x455l




That smd transistor at the left top of that 5E=3H ic tested short but when remove transistor is ok.

[piernov]

Re: Asus x455l

Sorry my mistake, the RAM power supply circuit is indeed related to your issue.
What's the resistance between the current sense resistor marked R010 on the first picture and the big coil on the bottom of your 2nd picture?

[mardocdor]

Re: Asus x455l

Sorry my mistake, the RAM power supply circuit is indeed related to your issue.
What's the resistance between the current sense resistor marked R010 on the first picture and the big coil on the bottom of your 2nd picture?

i measured it 1.5 ohm only... i try to removed that 5E=3H ic since i suspected it to be shorted but still there is that short...

[mardocdor]

Re: Asus x455l

by the way sir piernov do you have any idea if we can disable the internal ram and see if it will work using external ram?

[Isracons]

Re: Asus x455l

by the way sir piernov do you have any idea if we can disable the internal ram and see if it will work using external ram?

Hi, i'm new in the forum. I know it's been a long time since you posted this thread but i though this might be helpful for those who want to disable the internal ram.
In this video it shows how to do it, but it's for the model X550.

https://www.youtube.com/watch?v=YU8GylW-gQI&t=63s

It's a pretty rustic solution, and it doesn't explain very much, but it might be of use.
Hope you know spanish