USB malfunction due to short circuit!

Hey guys!

I was trying out some old hard drives via an external USB HD device, when one of them shorted my external USB HD device. I managed to fix the external USB HD device circuit since it burnt some component. But I think that while I was fixing it I somehow shorted the data connections in my laptop's USB port because I'm an idiot and should have unplugged the damn thing before attempting repairs. Anyway. As soon as Windows starts and without anything connected to any of the USB ports, a message appears stating that the device has malfunctioned.There are 4 USB ports in my laptop. I checked all of them for voltage and ground. All ports have correct voltage except for the one I used when messing around. This USB port's D+ and D- give 1V and are grounded which doesn't happen with the rest, which give 3V and are not grounded. I have tried following the data connectors through the motherboard but they disappear before I get to any component. Also my SD card reader doesn't work. My guess is that until I manage to (unground) those data connections, none of the other ports will work. This laptop doesn't have a PCMCIA so I don't know how to get at least one USB port in any manner! And I really need a USB port!!!! Any suggestions are greatly appreciated!!

Aspire 5738G Intel Core 2 2.0GhZ, 1066 MHz FSB + 4 unusable USB ports

THANKS!

 

Oh, Boy! Sounds like you may have done your board in there. I really hate to say it, but I think your ports are permanently shot. Your only hope now may be to get a USB card.

 

This is the standard USB connection,
Universal Serial Bus - Wikipedia, the free encyclopedia

Check from a true zero point (circuit ground) on the PC that 5 volts is present on pin 1.
Check that pin 4 has continuity to ground. I can't see that the current available via USB would be enough to open circuit a ground trace.

 

Thanks for the replies! I will check that out ASAP!

Ok these are the readings. All ports have 5V present on pin 1 and continuity to ground on pin 4. But both the data pins on 3 of the ports give me 3.23V while the port that seems to be damaged gives only 0.59V & 1.13V respectively. Not sure why I got data to ground on my first test and not this time. Maybe some component like a resistor has fried and until it is replaced, it will malfunction due to lack of voltage via data pins?? Any suggestions? Thanks again!

 

If you are patient enough to do the tedious work and the USB controller itself is still good you might be able to get it to work again. If you do it that way, use your meter to test the resistors, capacitors, transistors, etc. to see if they all come back with nominal values until you find the one(s) that are damaged.

If it turns out to be a big solder job you may still be able to revive it.

 

Thanks again for the reply, your getting my hopes up because I am very patient and I will be even more so in regards to my USB ports
Do I need to unsolder a resistor, capacitor or transistor to test it? Or can it be done while it is still connected? And I suppose the only way to know if the USB controller is still good, I would have to fix the damaged component first? Thanks again, I really appreciate your help and time

Just to clear things out a little, here is a picture of the issue itself.

http://www.spoton.comuf.com/MotherBoard/USBVoltages.jpg

 

Hard to say. I would have thought the data lines would be pretty immune to a short either to ground or 5 volts tbh.
I would be tempted to see if the 5 volts on the USB socket can supply current. A 47 ohm resistor would draw around 100 milliamps and the 5 volts should remain stable.
Could it be that the ports are no longer recognised due to some corruption. What if you uninstall via device manager and reboot and let windows pick them up again.

 

I already uninstalled the drivers via device manager but as sonn as windows starts, i get an error message staing that the USB device malfunctioned, even though there is nothing inserted in any port. I will try the 47 ohm resistor test as soon as I can.

 

Definitely try the resistor to load the supply although I doubt now it's going to be a supply issue as you have 5 volts present.

If it is a component that's zapped it's more then likely an IC rather than a discrete part. Can you trace where the pots go to or look up some of the IC types in that area to see what they do. U18 is it for instance... can't make the number out.

Was the external drive self powered. Is it possible that more than 5 volts has been applied to the port?

 

You should be able to test those components with them still connected to the board if the problem is not a short. If it's a short that is causing the problem, then you may have to remove the component, yes, but also depending on where the short is and you would be able to tell most likely if it were a short.

 

U18 is an AHCT125
http://www.datasheetcatalog.org/datasheet/philips/74AHC_AHCT125_2.pdf

Yes the external drive was self powered. It is likely that has happened, but I am not sure, really. I realized that when the computer is off, that's when the data pins are shorted to ground, which doesn't happen when it's on, hence my first test.

Here is what reads I got out of U18, remember to zoom in to get a better look

http://www.spoton.comuf.com/MotherBoard/U18GoodPort.jpg

http://www.spoton.comuf.com/MotherBoard/U18BadPort.jpg

Sorry if it's a little confusing, I'm trying my best here and I lack the expertise.
Thanks again!

 

Sorry for not seeing your post... subscribed to thread but not notified.

So the IC is a common 74AHC series.
If you look at the data sheet the AHCT type needs a supply of 5 volts on pin 14. This is missing in your first picture as you read 1.77 volts. Also you show pin 7 as having 3.25 volts on it. So something is very wrong there, yet in the next picture you show them as more normal sounding.

The voltage on pin 7 and 14 should be constant. Zero and 5 volts respsectively. Recheck them. Make sure your meter is correctly grounded. Any flux or laquer on the PCB acts as an insulator and can prevent correct readings. The voltages on the other pins can not really be measured with a DVM as they could be constantly changing data... that needs a 'scope to confirm the amplitudes correctly.

Check those supplies. Make sure that pin 7 is grounded correctly. It looks to go to a large ground plane so can not imagine a problem there really.

 

Thanks for the reply, Mooly. Don't worry, I really appreciate your help and time . I will check those values again as soon as I can, I could have made a mistake or as you say, the lacquer could have given me false measurements, although I did keep that in mind pressing and wiggling the meter's pins before writing the measurements down. I still use the laptop as always so I have to take it apart each time I want to check something out, which is kind of annoying and a bad thing for the mouse pad wiring. Although I'm getting so good at it, I might be able to get a job in China mounting laptops I'll try to build a temporary desktop in the meantime and have the laptop ready for testing. I did check some resistors to the right of the hub yesterday which gave me no value:R204,205,209,179,190,126,130,131,120,121 and 87. The thing is, those seem to belong to the GPU which is on the other side of the board. Anyways, I'll check the IC and more components soon, especially on the other side of the board and report back. Thanks again

 

I've noticed that through device manager, disabling and enabling Enhanced USB Controller 293A I am able to use devices such as pen drives and SD memory sticks but not a mouse, keyboard or most important of all, my midi keyboard. I will attach some screen shots of how it's done.

I also found a solution to share these devices through my network. I share the mouse and keyboard with Input Director a fantastic solution. And I share the midi keyboard and any other USB device with USB over Network, another great utility. I hope this helps anyone having trouble with USB's.

 

Hello again. I solved my problem with this USB Hub.
I figured out that the problem is not low voltage on the remaining 3 working ports, but low amperage amperage. Of course there is still something wrong, but since this hub is plugged in your computer and at the same time it's plugged into the main 230V outlet, it gives the amps it needs in order to work.
My next project is to find out how to get this amp shortage from within the laptop. Any suggestions are greatly appreciated. Cheers!

 

You need to trace one of the USB supplies back to the PSU in the laptop. If the supply is switched via a transistor that could well have failed or there may be a circuit protector (fuse) or fusible resistor somewhere.