USB Hub Current Overload Issue? - Page 1
Forum section: electronics / repair

author: otpowell
author_rank: Regular Contributor
timestamp: April 09, 2016, 06:31:38 pm
content: Hello my fellow EE enthusiasts. I have an issue. I have an old USB hub, which I wanted to use, and don't have an external power supply for. I wanted to be able to run a couple flash drives, charge my phone (0.9 A), and run my HackRF or another software defined radio.Since I didn't have an external supply for the hub, I bought a USB power supply which supplies 5V 4A.Today, I plugged that hub into my computer, then plugged in the 4A supply, I noticed that either the yellow/tan square capacitor or the chip under it was smoking. I immediately unplugged everything. NOW, the USB hub still works on other USB ports so I assume the hub is fine.The only issue is, the USB port on my laptop no longer works! Did I burn out the USB controller or voltage regulator on this specific port or something?Additionally, how would this happen? There was a load (my phone and USB flash drives) and loads only pull as much current as they need right? Why would the hub start smoking? My next step is to measure the 5V 4A power supply voltage to make sure it's only 5V, which I doubt that's the issue? Anyone have any suggestions on what the issue is, how to prevent this in the future, and how to fix my USB port. I'm going to pull apart my laptop soon and see if I can see any physical damage or bulging capacitors. Which I doubt I'll be able to tell because it's all surface mount stuff that's almost microscopic.I have various EE tools (oscilloscope, analyzers, etc) and even a USB microscope so I can usually run a few troubleshooting steps and take close up images relatively well.I disabled the USB ports in device manager and then reenabled them. I also unplugged the computer and removed the battery, and held the power button down while off to discharge any remaining electricity. I was thinking that maybe the computer turned off the USB port because It detected a surge of current or something but that did not work.Any suggestions would be greatly appreciated.Sent from my iPhone using Tapatalk

author: SeanB
author_rank: Super Contributor
timestamp: April 09, 2016, 06:46:03 pm
content: Is the power brick centre positive or centre negative, and does the USB hub power input match. The smoking device is a polyfuse, to protect the hub from overcurrent, and really the only way you can get it to trip without a shorted USB cable is to plug in the power to the external port backwards.Use a DMM to measure the voltage and polarity of the power supply, and do a continuity check on the power port to the hub to see how it is wired, and which power line the central pin connects to.Sadly if you applied reverse voltage to the computer USB port you will have blown the port, likely the polyswitch or other power switch on the port power itself and likely the actual silicon port drivers inside the chipset in the computer as well. Polyswitch fixable with care, but if the chipset is failed you are going to need to replace a thousand ball BGA package that was never designed to be replaced.

author: wraper
author_rank: Unknown
timestamp: April 09, 2016, 06:48:28 pm
content: First of all, square part is not a capacitor but resettable fuse. Secondly, are you sure the polarity of PSU connector is right. I guess you destroyed the power switch on that USB port.

author: wraper
author_rank: Unknown
timestamp: April 09, 2016, 06:52:05 pm
content: Quote from: SeanB on April 09, 2016, 06:46:03 pmHave not seen motherboards with polyfuses for USB for a long time. Almost any modern motherboard uses some kind of switch IC with built in current overload protection or something like this.

author: daveshah
author_rank: Unknown
timestamp: April 09, 2016, 06:53:32 pm
content: Is it just me or does U5 (presumably a regulator) look like it's let some smoke out?

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: April 09, 2016, 07:05:36 pm
content: Specs say it's a CP power jack on the power supply. So possibly the hub is CN? NVM hub is Centre Pos:Upstream Ports 1Downstream Ports 3Per-Port Voltage DC +5VPer-Port Current 500mA (max)Power Mode Self-poweredOperating Temperature 5º C ~ 40º CStorage Temperature -20º C ~ 60º CEnclosure PlasticPower Supply Output: DC 5V 2.4APlug Size: 3.5mm (outer)1.0mm (center)Plug Polarity: Center Positivehttp://www.belkin.com/support/dl/f5u217.pdf

author: stmdude
author_rank: Frequent Contributor
timestamp: April 09, 2016, 07:08:35 pm
content: Quote from: daveshah on April 09, 2016, 06:53:32 pmNope, it's not just you.OP: Can we get a closeup of U5 ?

author: otpowell
author_rank: Regular Contributor
timestamp: April 09, 2016, 07:52:17 pm
content: Quote from: daveshah on April 09, 2016, 06:53:32 pmYup, it has let some smoke out. Good observation sir.

author: otpowell
author_rank: Regular Contributor
timestamp: April 09, 2016, 07:55:30 pm
content: Quote from: stmdude on April 09, 2016, 07:08:35 pmHopefully that's close enough. I couldn't get any closer without losing focus. I can get my microscope out if needed. It did let some smoke out. Any idea what this means?

author: otpowell
author_rank: Regular Contributor
timestamp: April 09, 2016, 07:57:49 pm
content: Quote from: RGB255_0_0 on April 09, 2016, 07:05:36 pmThank you sir good idea googling it to pull specs and polarity. The polarity is correct, what now?

author: otpowell
author_rank: Regular Contributor
timestamp: April 09, 2016, 08:00:07 pm
content: Quote from: wraper on April 09, 2016, 06:48:28 pmThat's wraper, stupid me. I didn't see the fuse symbol initially. Thank you for noticing.

author: daveshah
author_rank: Unknown
timestamp: April 09, 2016, 08:01:43 pm
content: Hard to see but I suspect it had 33/3.3 on it at one point, and given the package, it's almost certainly a 3.3V or thereabouts LDO for the hub logic. I would first suspect reverse polarity, but as that has seemingly been ruled out significant over voltage due to the supply being unregulated (it looks fairly large and therefore likely not switch mode) must be the cause of damage - many LDOs are only rated up to 5.5V ish. Unfortunately it may have failed input to output short (very common), taking out the hub logic and quite possibly overvolting the data lines.

author: otpowell
author_rank: Regular Contributor
timestamp: April 09, 2016, 11:10:26 pm
content: Ok guys, polarity is the issue. The hub is CN and the jack is CP. The hub still works, that's a plus. Anyone know how to get the USB port back working again? Can I desolder the blown 5V regulator and rig up a 7805 regulator in it's place? Or maybe a zener diode? Surely there's a way to circumvent the components and bring power to the USB port again, seems like there would be anyway. Not sure how this works but maybe it's not as simple as that. lol. How do I pinpoint what the issue is? Guess we won't know until I open the laptop up and see what's going on behind that USB port.Sent from my iPhone using Tapatalk

author: otpowell
author_rank: Regular Contributor
timestamp: April 09, 2016, 11:39:48 pm
content: Well I opened up the laptop. No idea where to go with it now. The components are so tiny. The USB port which my finger is on is the broken one.Sent from my iPhone using Tapatalk

author: cowana
author_rank: Frequent Contributor
timestamp: April 09, 2016, 11:44:00 pm
content: If the controller of the hub is okay, you can hope that the USB data lines going into the laptop are okay, and the damage was just caused by feeding -5v up into the laptop's 5v USB connection.Being optimisic, that hopefully means the laptop's USB controller IC, and the damage is limited to the power circuitry supplying the USB port.There's often a FET, similar switch or current control circuitry to control power to the 5v line - this is likely the damaged part. Are you able to follow the PCB trace from the damaged port's 5v pin and see where it goes to? If it's on an internal layer, you could do the same by probing with a multimeter.If you're lucky, there might be a single component that can be replaced. What's the laptop motherboard make/model? Occasionally there are helpful schematics floating around the web!

author: otpowell
author_rank: Regular Contributor
timestamp: April 09, 2016, 11:45:25 pm
content: I just bought a brand new board for 20 bucks, do you guys think this will fix it?Sent from my iPhone using Tapatalk

author: cowana
author_rank: Frequent Contributor
timestamp: April 09, 2016, 11:48:10 pm
content: Quote from: otpowell on April 09, 2016, 11:45:25 pmAlmost certainly.Each of the three ports has an 8 pin IC near it (two are visible on the bottom of that seller's photo) - my money would be on the one closest to the blown port being damaged - thus a new board would replace it and get it working again.From the pinout, I think it's a P channel MOSFET switching the 5V line.From your photo, the middle chip (nearest the 'S' of Sony on the bottom of the board) seems to have a burn mark on it - is this actually there or just a bit of dirt?Andy

author: amyk
author_rank: Super Contributor
timestamp: April 10, 2016, 12:09:46 am
content: You can find the schematic for your laptop (Google "Foxconn M960" and look for the Vietnamese site) and it shows those MSOP-8s connected to the USB ports areG545 Power Distribution Switches. A quick Google shows that it's pretty common for those to fail if the USB ports are subjected to abuse, and also this thread comes up saying a TPS2065 is a suitable replacement:https://www.eevblog.com/forum/projects/g545-mosfet-power-switch-alternative/(The TPS2065 looks to be a little better, since it has a 70m MOSFET vs 100m RDSon for the G545)

author: otpowell
author_rank: Regular Contributor
timestamp: April 10, 2016, 12:41:25 am
content: Thank you guys. Honestly I've already closed the laptop up so I'm not sure if it's a burn mark. I looked at the board for a while and didn't notice any burn marks. Even if I was able to get a replacement G545 or TPS chip, my surface mount soldering skills aren't that great so I'm glad I bought a new board. Save me the mess of desoldering and tracing and all that. Not that I don't enjoy to do all that, I really do, but I have a ton of other stuff I can do that on. I have other projects that I'm working on and this came at a bad time. It just bothers me that I have a bad USB port ya know. At least the replacement is on the way. Thank you everyone for all your research and feedback to help me fix my issue. I really do appreciate it. Your guys here in this forum are the smartest guys on the web in my opinion.Sent from my iPhone using Tapatalk