Thread: Powered USB hub 5v feedback

For those of you who measured the voltage from the hub on the upstream port, was the voltage present on the 5v power line or the data line?

Since the hub is powered, I'm wondering if simply disconnecting the 5v line between the PC and the hub would solve the problem. Of course that doesn't help if the voltage somehow leaks to the USB D+ line.

Hi, problem in my case was voltage leaking from 12v powered devices that have USB connections to the PC. This USB interface in these powered devices would Phantom power the +5v USB line to around 2.8 volts, prior to the PC starting (powered on). As the +5V/standby USB line is common to everything in the PC and every internal/external device powered from +5v, including things the SSD. That voltage is enough to part power some devices (especially devices without brownout protection) and cause them to be not ready or locked when the PC boots.

There is also the problem of some powered Hubs leaking back to the same +5v line and causing the same problem if they are powered before the PSU +5 line is active. They need to come up at the same time as the PSU as there are timing requirements for initialisation of SOME USB devices to consider.

The 5 volts was on the power line, not the data line. I tried cutting the 5 volt line and it worked but had other consequences that I cannot remember at the moment. I thought I explained them in this thread but I'm too lazy to go back and read the thread right now... Sorry.

Definitely the easiest solution was to get a good quality hub. I purchased one from radio shack and it has been fine for the last several months.