Asus N550LF LAN components burned

[tofik]

Hi guys,

Could you help me identify burned components on asus N550LF mainboard please?

I am sure that main LAN IC is burned, this is the Realtek 8112G.

Please check photo attached with burned components, tracks are easy to repair, resistor is 75 ohm but what could be that big capacitor which seems to be dead and three others probably capacitors (tiny ones).


Any suggestion would be much appreciated

[tofik]

Re: Asus N550LF LAN components burned

UPDATE:
- replaced main IC of the Ethernet controller (Realtek 8112G),
- restored all tracks,
- replaced all 75 ohm resistors,
- replaced 1000pF / 2 kV capacitor,

Did not touch these 3 tiny caps, I am not sure if these are really important.

Anyway Ethernet controller is still dead, I mean in Windows device manager it shows as not connected (drivers are fine).
Any suggestions what I could check now?

Thanks

[mon2]

Re: Asus N550LF LAN components burned

There must be some interconnect or part that is defective on the rj45 side.

Review the 75 ohm resistor network array. Confirm it is still at 75 ohms. Also the long inductor (?) that is beside the array. What is the resistance across this part? It looks burnt.

This board had a lightning surge travel through it to cause this damage.

Best to review a realtek example schematic for this part to understand the parts required to rebuild it.

May be easier to use an Ethernet USB dongle. They are cheaper than underwear from Amazon.

[tofik]

Re: Asus N550LF LAN components burned

Thanks for your response,
You are correct, board had a lighting surge.

Saying Ethernet controller is still dead, I meant Ethernet controller is completely not visible in Windows device manager.

75 ohm resistors are 100% fine, cheched them twice.
That long inductor is a 1000pF / 2 kV capacitor (Bob Smith termination), also has been replaced.

"Best to review a realtek example schematic for this part to understand the parts required to rebuild it." That's the best advice, I will into it in future, for now I just ordered Ethernet - USB dongle, brand new Dell 470-ABBT for $13, should be alright.

[mon2]

Re: Asus N550LF LAN components burned

Flux the replacement ethernet controller well and allow it to naturally swim onto the PCB pads. The controller must be enumerated by the host controller and appear in the device manager (Windows) before testing the back end with the rj45.

I do have some pinouts for the Realtek 8111G which appears to be similar in pin count and can post it if there is an interest.

[tofik]

Re: Asus N550LF LAN components burned

Flux the replacement ethernet controller well and allow it to naturally swim onto the PCB pads. The controller must be enumerated by the host controller and appear in the device manager (Windows) before testing the back end with the rj45.

I did use a flux, it should not be a problem, I visually checked every single pad under scope, I am more worried I bought a fake 8112G chip, ordered it from Aliexpres.

I do have some pinouts for the Realtek 8111G which appears to be similar in pin count and can post it if there is an interest.

That would be helpful please

[mon2]

Re: Asus N550LF LAN components burned

I think fake chips are an overrated concern but of course buy from a vendor with a high store rating. Personally like SUHMS but there are others. Even consider to buy the same part from multiple vendors since they are so cheap.

It is a twisted market strategy to lock down parts with unique part numbers. If I see Realtek at the next trade fair, will give them an earful. Did this with NEC in the past who had local agents trying to sell the USB bridge for more than the finished product from offshore. Different pricing for USA market than China.

Let me take some screen grabs of the protected datasheet and post them here in a few.

[Stevedb]

Re: Asus N550LF LAN components burned

I think fake chips are an overrated concern but of course buy from a vendor with a high store rating. Personally like SUHMS but there are others. Even consider to buy the same part from multiple vendors since they are so cheap.

Hi Mon I got also fake chips from SUHMS . I ordered 5 audio ic IDT 92HD91B2X5NLG and none off them worked. He refund me . But were also fake.

Regards
Steve

[mon2]

Re: Asus N550LF LAN components burned

See attached. This may be the pinout for the Realtek 8112 QFN package. Confirm it by reviewing the power and ground pins.

Just noticed, the pinout for the 8112 appears to be a USB to Ethernet controller.

The 8111 Realtek is a PCIe to Ethernet controller.

First of all, can you confirm that we are dealing with a 48 pin QFN package? 12 pins per side on your device? That is what is showing on the Aliexpress stores.

[mon2]

Re: Asus N550LF LAN components burned

I got also fake chips from SUHMS

Wow. That is not good. I know that the store vendor is very responsive and quick to act when there is a concern but good to know. At this time, we cannot justify an x-ray machine which run $50k-$100k USD but that is on our tools to acquire. Often, then you can compare the original die photo against the new purchase.

[tofik]

Re: Asus N550LF LAN components burned

See attached. This may be the pinout for the Realtek 8112 QFN package. Confirm it by reviewing the power and ground pins.

Just noticed, the pinout for the 8112 appears to be a USB to Ethernet controller.

The 8111 Realtek is a PCIe to Ethernet controller.

First of all, can you confirm that we are dealing with a 48 pin QFN package? 12 pins per side on your device? That is what is showing on the Aliexpress stores.

Thank you very much for your message,

The one which I bought is 32 pin package, 8 pins per side.
I ordered from that guy, here is a link: https://m.pl.aliexpress.com/item/400...yAdapt=glo2pol

The original one was the same, see attached.

I checked aliexpress store rating and it's really low, only 88% of positive reviews and rating of 3,6.