Dell Latitude E6540 2 right side USB dead

[Andreasbest]

Hello
I received a Dell E6540 today, everything works fine except the 2 right side USB JUSB3 & JUSB2 ,they are completely dead regardless what USB devide i tried.
There is no physical damage on them and look perfect, there is no 3.3v in D90 and D89 when i insert a USB device.
Any advice?
Donor MB available

Schematics and boardview attached.
Thank you in advance!!

[mon2]

Re: Dell Latitude E6540 2 right side USB dead

1) U93 is the local current protected load switch for JUSB3 connector.

2) meter in DC voltage mode; with the adapter connected, what is the voltage on pins 2 & 3 of U93 ?

Then voltage on pins 6,7,8 ?

3) same question for U91, pin 2 & 3 voltage reading ?

Then voltage on pins 6,7,8 ?

[Andreasbest]

Re: Dell Latitude E6540 2 right side USB dead

1) U93 is the local current protected load switch for JUSB3 connector.

2) meter in DC voltage mode; with the adapter connected, what is the voltage on pins 2 & 3 of U93 ?

Then voltage on pins 6,7,8 ?

3) same question for U91, pin 2 & 3 voltage reading ?

Then voltage on pins 6,7,8 ?

Hello!
U93 is missing from these MB (LA-9413), although U91 is soldered.
U91 has 5v on pins 2 & 3, 0v on 6, 7 & 8

[Andreasbest]

Re: Dell Latitude E6540 2 right side USB dead

[deleted]

[mon2]

Re: Dell Latitude E6540 2 right side USB dead

I am suspecting that the usb load switch is damaged and needs to be replaced. They are very common and available from many different vendors.

You could, swap the usb load switch that is working to the side that is not working to validate the usb ports still function. Without Vbus, the docked usb host powered device will not function.

Or you could test with a usb cable to other external self powered devices.

[Andreasbest]

Re: Dell Latitude E6540 2 right side USB dead

I am suspecting that the usb load switch is damaged and needs to be replaced. They are very common and available from many different vendors.

You could, swap the usb load switch that is working to the side that is not working to validate the usb ports still function. Without Vbus, the docked usb host powered device will not function.

Or you could test with a usb cable to other external self powered devices.

I have a donor MB here, if i understand correctly you want to replace U91?

[mon2]

Re: Dell Latitude E6540 2 right side USB dead

1) Check and post the voltage on pin #4 = EN# for this loadswitch. Being active-low, this pin should be LOW to enable the flow of the voltage from logic board to the USB VBus pin on the local usb connector.

What is the reading here ?

2) Also post the voltage on pin # 5 = OC (over current flag). This pin is used to flag the host USB controller that something nasty on the USB connector(s) has consumed too much current so shut it down !!

Aside from the above notes, believe that this load switch may be defective. First check if the switch is being enabled or not. Then ok to swap U91 with a known good or from a donor and check again.

[Andreasbest]

Re: Dell Latitude E6540 2 right side USB dead

1) Check and post the voltage on pin #4 = EN# for this loadswitch. Being active-low, this pin should be LOW to enable the flow of the voltage from logic board to the USB VBus pin on the local usb connector.

What is the reading here ?

2) Also post the voltage on pin # 5 = OC (over current flag). This pin is used to flag the host USB controller that something nasty on the USB connector(s) has consumed too much current so shut it down !!

Aside from the above notes, believe that this load switch may be defective. First check if the switch is being enabled or not. Then ok to swap U91 with a known good or from a donor and check again.

Replacement of U91 fixed everything, thank you very much!!!