Why is my serial usb cable not working?

Tech Support: Why is a 10 meters USB 2.0 cable (no repeater) working on my laptop?

• A few months back when I bought my 10 meters USB cable it could not work on any of the USB 2.0 ports. I learned later that the maximum USB 2.0 cable distance is 5 meters and also you should use a powered hub or active repeater cable if you want to extend it to more than 5 meters. Last week when I bought a new laptop. I decide I would buy the 10 meters active repeater cable from Amazon. But before I bought it I tested my old 10 meters 2.0 cable on the new laptop. Guess what? It worked (only on one USB 2.0 port and the USB 3.0 port). Transfers to my flash were between 5-7 MB/s. It even worked with my USB 3G modem very well. The good news is that I've saved myself some money. But I want to know why it doesn't work on the other USB 2.0 port? And more importantly, why is it working with a 10 meters cable? NB: The 10 meters USB 2.0 cable has no repeater and it's just the normal USB cable used to connect computers to printers. Here is a link to a cable that is similar to mine: http://www.dhgate.com/product/new-usb-2-0-a-male-to-female-extension-cable/128851598.html Note the two ferrite beads are for reducing EMI and are not repeaters.

• Answer:

  some basic troubleshooting before any answer can be given: do your other ports work otherwise? does unplugging one or more of the devices from the long cable help? is your port that works in fact an USB3 port whilst the other are USB20? are the other ports close to each other? (it could mean they share the same controller) does your PC's user guide explicitly state that the current on certain ports is limited? how many USB devices do you have in your system, and in what configuration? do  you have any devices that require a lot of current? scanners,  harddrives, usb headphones with an integrated amplifier, LED lamps,  anything that draws >100mA/ >0.5W? - this is usually specified on the sticker of the device does any of the previous devices have its own 5V supply? do you have any obvious sources of electrical noise nearby? Speakers near the cable, mains cable near the USB, light or fan dimmers; communications tower next to where you live? can you test the system with a shorter cable and see what happens? Did you mean mbps as in megabit/s = 500-750 Kbytes/s?. Either way, this transfer rate is remotely acceptable for a modem. An USB2 harddrive or flash drive should get in the upper 50MB/s (unless they are very cheap models) USB2 is theoretically limited to 480mbit/s by specification. With your long cable, it is unlikely to reach this 60MB/s. It is very unlikely you will get a definite answer for this one if none of the above yields an obvious solution. If this is for a company and you call a specialist IT/electrical contractor, they will shrug it off and say that it is below the standard. In this case, they would probably recommend an Ethernet to USB solution. CAT6a cable can go to considerable lengths without much signal loss. An even more expensive solution is Power over Ethernet, that can supply DC voltage up to 48V (this would solve the problem of providing power in the other end, if there is no possibility to do so)