HP 355 G2 Left USB Ports and Ethernet Port not working

[Fluxi_77]

Hello Guys,
I currently have a problem with an HP 355 G2 where the right USB Port works without a Problem but the left ones and the Ethernet port which is also in the region of the two USB ports are not working.
The HP Hardware Diagnostic tool also shows them as faulty. I used a USB tester and it also shows that I don't have 5V on the ports so I suspect a problem with an IC that controls the Voltages that goes to this ports.
Unfortunately I found no boardview or schematic for this device and I am a newbie in tech repairs so I don't know where to start. Other than this problem the laptop works fine.
Could someone maybe guide me where to look for and what measurements I could do to get more information on the fault.
Thanks in Advance!

[FriedFred]

Hi! Is this board on the left side connected with a ribbon cable?
It's likely unusual that the USB and LAN power has a problem at the same time. Only if there is a problem with the connection of this ribbon cable, maybe.
They don't share the same voltage, I think. For example, the USB has 5V, the LAN has 3.3V and less. So, there can be a problem with a higher-order voltage rail from where the lower-order voltages are generated.
You can check with the beeper of your multimeter, whether the 5V-pins of the USB ports are all connected together. Probably you can find a disconnection.

[Fluxi_77]

No the port which is connected with the ribbon cable is at the right side and this port works fine. But I could do the multimeter check tomorrow if that helps narrowing down the problem.
Thanks in the meantime for answering

[Fluxi_77]

I have now done the test and both pins 1 which are displayed in the image have a continuous path to ground which is probably not good... The Pin 1 of the ethernet port on the other hand is not connected to ground.
Where could I continue?

[mon2]

Flux and remove the esd diode array you show behind the usb connector (D***). Test the resistance again without this esd TVS array.

[Fluxi_77]

Should I remove both of them behind each connector or just one and test that connector?

[mon2]

Each TVS diode is local to the usb connector. Before you start, locate nearby a local usb switch. This local usb load switch acts like a current limit switch for vbus.

Often, it is the load switch that gets killed. Share a pic of what is onboard near the usb port.

[Fluxi_77]

This is front and back... Hope you can read something.. If you want a more detailed image of a specific chip I can use the microscope to make a photo.

[mon2]

Unable to locate the local USB load switches in the posted pics. Review the opposite side of the USB connector area. The load switches may be soldered in that region.

[Fluxi_77]

With these four images and the two from before you should have the whole board. Sorry it is difficult for me to take good photos because I don't know what to look for.

[SMDFlea]

Unable to locate the local USB load switches in the posted pics. Review the opposite side of the USB connector area. The load switches may be soldered in that region.

In the second picture at post 8 ,bottom right hand corner U2400 https://www.mouser.com/ds/2/115/AP2820-271651.pdf

[Fluxi_77]

Okay thanks how can I check if it is faulty?

[Fluxi_77]

I measured a connection to ground on all three Vout pins.

[mon2]

Flux and remove this load switch. Then test the resistance to ground again without this part on the board.

[Fluxi_77]

Short is still present on all three Vout pads

[mon2]

Flux and remove the ESD device mentioned earlier but the one that is near the USB connector under review.

[Fluxi_77]

Removed both but Vout still shorted. You meant these ones right?

[mon2]

Yes. Ok - hunt for a local bulk capacitor that will be camped onto the same Vbus line. By USB specification, this bulk capacitor is often 100-120uF. Flux and remove it when it is found.

[SMDFlea]

Short is still present on all three Vout pads

Have you looked inside each USB socket for bent pins, dirt, liquid damage, corrosion etc

[Fluxi_77]

Yeah the pins look fine... How do these bulk capacitors look and how can I measure the F value. As I said I am a newbie so sorry for that