Erratic USB Performane on Dell 5420 Laptop

[RogueTrader]

I am troubleshooting subject laptop USB ports which have displayed signs of connecting/disconnecting. The laptop has three USB ports, two USB 3.0 SuperSpeed, the other is not SuperSpeed.
When I plug in the USB 3.0 Loopback Plug, one of several things happen: 1) the loopback plug is not detected at all; 2) the loopback plug is detected, and tests successfully at full speed, but not the highest speed; 3) the loopback plug tests successfully at the highest speed. All of this seems random, and non-repeatable. I have updated the chipset and all manner of drivers from the Dell support site. It seems unlikely that all three ports would fail, so I am exploring any similar instances to see if a common problem/solution has been found. Thanks for considering my issue.

[David (PassMark)]

1) Confirm the USB3 plug is working correctly, and the fault is really on the laptop, by testing plug on another machine. I assume the plug and it's cable are fine, as you wouldn't be doing this unless the Laptop had prior problems.

2) Do a close up inspection on the USB ports (macro lens or microscope). Maybe the customer had some bad device / bad cable that they used to systematically damage the connectors. Customer plugs in bad device, which doesn't work, so they try the next port, which works briefly then also fails. So they try the third port. And voila, you have a laptop with 3 bad ports.

3) Similar to 2 but the bad device does electrical damage to the USB host controller chip. For example the bad device has a short circuit between the voltage line and the data line. Or the bad device applied a high voltage on a line it shouldn't have. The host controller chips typically can't protect themselves against possible scenarios. Unfortunately internal damage to the chip on the motherboard won't typically be visible. But likely you'll need a new motherboard as nearly no one replaces these chips.

4) Reset BIOS and do clean install of Windows. Remove all other connected USB devices & hubs before testing. Just to confirm the problem is hardware and not software.

5) Check voltage levels from the ports. Our plug does this. Check both on mains power and battery power.

6) If you really want to get to the bottom of it, get a usb3 protocol analyzer and oscilloscope. This is difficult, technical work however.

7) A quick search of the internet showed several people with the same model had the USB connector come loose from the motherboard, then become intermittent. e.g. to much force applied to the plug and / or the soldering to the motherboard not being very robust. USB connectors, especially Type-C are pretty fragile. But as there are so many wires on a type-C connector (20) an the pitch is so fine, they are very hard to re-solder. You need to be an expert solderer and have the right gear.

[David (PassMark)]

This comment from Reddit was for the Dell 5410, but you get the idea.

[RogueTrader]

Thanks for the insights, very useful.

1} The USB3 plug works perfectly in another, newer laptop.

2} Inspection with a high power magnifying glass reveals one of the port's gold pins is at a slightly lower level than the others. Not much, but perceptible. I'm thinking this might account for erratic performance, sometimes working, sometimes not, or at different speed levels. Your thoughts?

3) Standing by on the motherboard possibility, but likely this unit is not repairable given its age.

4) BIOS reflash/update accomplished, no change in symptoms

5) Both on mains and battery, voltage fluctuates between 5.01, 5.02, and 5.03.

6) This one is beyond my capabilities, will consider taking to professional shop.

7) This, also, is beyond my capabilities.

Laptop also has a USB-C port; I'm working on getting the right connections to connect the tester.

[David (PassMark)]

the port's gold pins is at a slightly lower level than the others. Not much, but perceptible

Obviously if the pin doesn't make electrical contact it could be a problem.
Even if we had a photo I think it would be hard to judge if it was an issue.

Some pins on Type-C are redundant however. If you flip a Type-C cable up side down it might work as different pins would be used.

[RogueTrader]

Final report here. I was able to to connect the USB3.0 loopback tester to the USB C port. It was reliable, always connecting at the highest rate of speed. Tests were flawless at the highest rate.

I'll just forgo using the USB 3.0A ports, and get a 3.0 hub to run off the USB-C port. This will be a workable solution for me.

Using the USB3.0 Test Plug, I was able to confirm that each of the USB Type A ports has a problem, and can't be used reliably. It also demonstrated the USB-C port was perfect. Thanks for the help on this!

[David (PassMark)]

Glad it got sorted out, or mostly sorted out.