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**Scenic** · 01-30-2011, 05:36 PM

Re: ESD damage to laptop's USB ports

usually, double-USB ports (stacked on top of each other) share one fuse for +5V.
at least on normal PC motherboards..

some of them are self-resetting, some are ordinary surface mount fuses. might be semi-dead, as self-powered devices work fine..

**gretti** · 02-01-2011, 04:00 AM

Re: ESD damage to laptop's USB ports

I have had that same issue before on a 600m. I had to reflow the southbridge to get the USBs to work again. However since they work working before you started swapping USB drives, I don't know if this is your problem. Did you remove the board from the case? you may have cracked a solder joint somewhere.

**jarl** · 02-03-2011, 10:32 AM

Re: ESD damage to laptop's USB ports

Thank you for your answers,

@gretti: do you mean that after a static discharge you had to reflow the southbridge?
The mobo has been out of the case once or twice, but it was a really long time ago, so I tend to believe the problem has nothing to do with a crack or anything like that. I have read about other people who have had similar problems, who are using their peripherics with a powered hub and stuff like that. But I'm moving this laptop all the time and having an extra cord is not an option.

@scenic: I think only *very* cheap USB devices use fuses as their main protection against discharges (it seems to be "forbidden" on the USB spec), and most probably these laptops use a self-resetting device (a PTC?). Also, if it was a fuse (it looks like sometimes there are fuses as an extra protection), there wouldn't be 5V on the USB port, right?

So, the question remains: on these particular laptops (ok... I suspect they use a similar approach on several computers), what gets fried when there's a ESD?

**ablacon64** · 02-03-2011, 10:47 AM

Re: ESD damage to laptop's USB ports

Maybe it's nothing about ESD, check the data terminals soldering, one may be cracked.

**ratdude747** · 02-03-2011, 04:28 PM

Re: ESD damage to laptop's USB ports

i see the problem

you have a the i855 chipset. you need a new mainboard. they like to randomly blow the usb... my latitude d400 did last week and i just fixed it with a new mainboard.

sorry to have to tell you that, but thats what it likely is.

**jarl** · 02-04-2011, 01:08 AM

Re: ESD damage to laptop's USB ports

Hello ratdude,

I can't find anything about failed i855 chipsets. What are the symptoms? When these chipsets "blow" the USB, does it continue working with self-powered devices?

If the USB ports were dead I would just assume it was something major. However, since there is 5V in the power line, and self-powered devices work fine, my guess is that whatever current-limiting device is used to protect these ports was damaged by ESD. Also, do you know if the USB ports on the docking station are driven by the laptop's chipset? Because those are working without flaw.

Now, why my insistence it *probably* has to do with ESD: I was (and continue to be) shocked by ESD several times that day, except I was being careful to touch bare metal before handling ESD-sensitive devices (laptop & memory stick) every time I had to move around. After many hours of work (i.e tired/sleepy), I unplugged the thumb drive and had to stand up to pick up a CD (and walk on a carpet) with the thumb drive in my hand. When I plugged the thumb on the laptop it didn't work. I assumed I had fried the thumb drive but, alas, it was something else. I think it's too much of a coincidence that any mobo crack / chipset error / etc. showed up it's rear end right then and there. Of course I may be wrong, but to me this points to a ESD problem

**ratdude747** · 02-04-2011, 02:30 AM

Re: ESD damage to laptop's USB ports

no, the opposite happens. you have power and overcurent monitoring but the data part dies. by blow the usb, i meqnt the usb function of the chipset goes (but anything connected is A-OK).

symptoms:

- NO usb function
- controller detected in device manager (windows ) or lspci (linux via terminal)
- 5v+ still exists on ports
- all other devices function

the best way to test for 5v+ would be to find something that just power will make it do something (ipod (charging), some usb mice, usb book light, etc.)

It was mentioned in my dead usb thread:

https://www.badcaps.net/forum/showthread.php?t=13143

it was more of a noticed pattern be a member who has seen a LOT of laptops. what causes it is not to my knowledge but it id a chipset issue, only fixable by a trip to ebay for a new mainboard. hopefully you can get it cheaper than i did since your model has a socketed cpu (while mine is a soldered BGA).

if you do not mind not being able to boot from usb, the other option is a usb 2.0 PCMCIA card. you should still have power from the dead ports, so the card's power cord can be plugged in. cheaper and easier, but bulkier and uglier (and non-bootable). If yours has the bluetooth module in it (iirc you model has that option), then you will not be able to use the module with this option.

**Scenic** · 02-04-2011, 02:36 AM

Re: ESD damage to laptop's USB ports

sounds like the same problem the ICH5 southbridge (used on socket 478 boards with i865 and i875 chipset) used to have..

http://en.wikipedia.org/wiki/Intel_ICH5#ICH5

**jarl** · 02-04-2011, 01:10 PM

Re: ESD damage to laptop's USB ports

Thank you for the answers, people, but as I stated on the original post the USB ports *are working*. The only problem (albeit a large one) is that there doesn't seem to be enough power to drive non-self-powered devices. Again, I can use external DVD drives, external hard drives, etc, as long as those devices don't draw their power from the USB port.

The USB spec requires 500mA to be available at the ports; the USB-specific current-limiting devices I have seen usually cite 1.5A as the upper limit (check for instance the TI TPS2062). I don't think this ports are providing more than a few (50mA? How much a thumb drive requires?) mA. My guess is that a device like this is fried, but I can't find any mention of these things on the 600m

**ratdude747** · 02-04-2011, 02:10 PM

Re: ESD damage to laptop's USB ports

sounds like a cold/cracked solder joint in the 5v...

**jarl** · 02-04-2011, 02:20 PM

Re: ESD damage to laptop's USB ports

Well... it looks like it as a self-resetting device after all.
I left the laptop disconnected and without a battery for several hours in preparation for "exploratory surgery", and after my last post I decided to open it up. I decided to try the USB port once more, though, to make sure I had the symptoms of the problem straight. Lo and behold, the USB ports have accepted everything I have thrown at them

Just for the record: when the problem first showed up I tried removing the battery but it didn't help. Either I didn't removed it long enough, or the ESD was still present, or -something-. Leaving the laptp for a few hours without any power source did the trick.

I just hope the life of the device wasn't shortened... This laptop is the one I use when I need to abuse a machine.

Thanks for taking the time to answer!

**ratdude747** · 02-04-2011, 04:18 PM

Re: ESD damage to laptop's USB ports

you should be fine.

glad it is self curing... wish my issue was... but oh well, at least I got a nicer cpu out of it.

**ratdude747** · 03-16-2011, 05:37 PM

Re: ESD damage to laptop's USB ports

fate is a B****, isn't it... my rear usb port has done the exact same thing as described. the left one works, as does the internal one for the bluetooth... once i have time to leave it for a few hours w/o battery, I will try that.

**PCBONEZ** · 03-16-2011, 06:49 PM

Re: ESD damage to laptop's USB ports

Keep in mind the amp limit on USB is 0.5 amps per port. [ 500 milliamps. ]
Most modern laptop hard drives exceed that.

**ratdude747** · 03-16-2011, 06:54 PM

Re: ESD damage to laptop's USB ports

45min wait w/o battery didn't fix it.

bummer

at least I have a hub... for mice and game controllers only (no rumble).

**tronxkid** · 07-01-2011, 05:22 PM

Re: ESD damage to laptop's USB ports

Is it possible to provide +5v to the faulty USB port and fix it?
I mean USB data pins are working So If we can provide external +5v It should work (I guess so)

If its not possible, please tell us why?

**PCBONEZ** · 07-01-2011, 08:07 PM

Re: ESD damage to laptop's USB ports

That would probably work if you also disconnect the original power source.

Bear in mind the USB power has filtering to prevent EMI from coming through the attached cable and feeding the EMI back into the motherboard's power rails. [The length of attached cable inheirently acts as an antenna.]
EMI on your +5v rail won't make for a stable system.

Also there is presumably some kind of over-current and surge protection to protect both the device and the motherboard.
[This may simply be a fuse.]

IOW: It could be done but it's not as simple as installing jumper wires.
.

**tronxkid** · 07-02-2011, 03:20 AM

Re: ESD damage to laptop's USB ports

Originally posted by PCBONEZ View Post

That would probably work if you also disconnect the original power source.

Bear in mind the USB power has filtering to prevent EMI from coming through the attached cable and feeding the EMI back into the motherboard's power rails. [The length of attached cable inheirently acts as an antenna.]
EMI on your +5v rail won't make for a stable system.

Also there is presumably some kind of over-current and surge protection to protect both the device and the motherboard.
[This may simply be a fuse.]

IOW: It could be done but it's not as simple as installing jumper wires.
.

thanks for the input pcbonez. I think I should learn more about power management of USB and stuff. Actually I thought about installing jumper wires.

**joshnz** · 07-02-2011, 06:29 AM

Re: ESD damage to laptop's USB ports

Powered usb hub is the way to go.

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ESD damage to laptop's USB ports

ESD damage to laptop's USB ports

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