Low Voltage USB Ports and USB External HDD Problem

I'm facing a low power USB port issue on my desktop PC. I have a USB 2.5" external harddrive and it does not work with any of the USB ports on the computer case except for one.

Also if I use a extension cable with that port, the HDD will not work. I measured the voltage of the USB ports and they gave me about 4.60-4.70V. I updated the BIOS to the latest version. My motherboard is an AUS M4A785TD-V Evo and my power supply is Xilence 700W.

Is there any way to increase the voltage of the USB ports?

zforx

Posted 2011-06-05T13:25:49.673

Reputation: 235

does the port work with other devices? – None – 2011-06-05T15:30:49.470

bckbck, obviously, I cannot say for sure, but it probably works fine with many devices that require less power. I got the sense that the external drive he is using might be powered solely by the USB port, making power critical. A mouse will use a lot less, and probably work fine. – KCotreau – 2011-06-05T16:03:29.073

A)How are you measuring the voltage? B)Have you tried another PSU? Also, it is very silly that you didn't think about or didn't mention about 'B'. – barlop – 2011-06-05T16:32:58.700

@bckbck yes wireless mouse and keyboard, and other usb devices are working on my pc. They require less power than usb hdd. – zforx – 2011-06-06T14:35:19.273

Answers

I doubt you can change it on your computer. You should probably buy a powered USB hub. Google "powered usb hub" without the quotes.

KCotreau

Posted 2011-06-05T13:25:49.673

Reputation: 24 985

I know external powered usb hubs but I want to know why my pc does not give 5V on usb ports. – zforx – 2011-06-05T13:39:33.850

The specification for USB is +5 DC volts. I don't regularly (by that, I mean never have) measure the voltage on USB ports, but 4.7 seems like it may just not be working right, and the hardware is bad. I would probably call ASUS and ask them about it, and if it is a problem, as I suspect, have them RMA the board. Does the external drive have its own power source? – KCotreau – 2011-06-05T14:05:10.240

External drive does not have it's own power source, and it is working with my laptop which give +5V when I measure it's usb ports. – zforx – 2011-06-06T14:31:39.870

They make usb Y cables that use 2 usb ports to properly power the drive. It draws power from 2 usb ports.

http://www.amazon.com/Apricorn-Power-Adapter-Cable-AUSB-Y/dp/B000JIOHDE enter image description here

Moab

Posted 2011-06-05T13:25:49.673

Reputation: 54 203

USB low voltage can impact a hard drive. I have an Apple (Fujitsu make) drive my brother gave me. I put it in an external USB 2 enclosure and used a USB connector with a Y (double USB ends)to plug into an nGear powered USB hub and then to my computer. The drive would mount and unmount and I could never complete a clone of my internal drive. I ended up just plugging it directly into one of my Mac Mini's USB port (just using one of the USB ends) and I didn't have any further problems. This leads me to believe that hard drives are especially sensitive to power sources as the Y connector didn't seemingly provide enough juice (even double plugged in with a powered HUB). Also, my 2012 Mac Mini has USB 3.0 which I understand provides more power (in the range of 900 mA verses 500 mA for USB 2). This boost may have helped things.

Andrew

Posted 2011-06-05T13:25:49.673

Reputation: 1

Welcome to Super User! This is really a comment and not an answer to the original question. To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient reputation you will be able to comment on any post.

– DavidPostill – 2015-10-13T14:19:24.950