Powered USB Hub

frogdoctorfrogdoctor Toronto, On
edited January 2006 in Hardware
Last week I bought a new APC 4 port powered hub. My keyboard (normal type, not USB) hangs up, after I power up. Could not figure it out until I wanted to go to bed. Turned my PC off, turned my worklight off, but there was still a blue glow coming from the PC! What the #&^%*! I pulled the AC cord out, still blue light from the power supply! I shut down the power bar and all was black. Troubleshooting found the power backfeeding to the motherboard from the USB hub. I had another APC 4 port hub, and it never did this. After I beat up my friend, and stole my old USB hub back from him, I reinstalled the old hub and all is well.
Anyone come across this before?

Comments

  • tmh88tmh88 Pittsburgh / Athens, OH
    edited January 2006
    If you never had this problem before, and the old hub is working again, then your new hub is probably messed up, or could need some drivers(if there are, ive never used a hub). As for that blue glow sometimes theres still a little electricity flowing and will take a few seconds for the light to dim out, but thats still kinda strange. I know my amp for my guitar does that. Even after i unplug it, the LED stays lit for maybe like 4 seconds and then dims out.
  • frogdoctorfrogdoctor Toronto, On
    edited January 2006
    The lights stayed on for 0.5 hours before I shut off the power bar. I thought I had invented a new power source! Then I came back to reality. The old hub does not have as much power output as the new one.
  • tmh88tmh88 Pittsburgh / Athens, OH
    edited January 2006
    frogdoctor wrote:
    The lights stayed on for 0.5 hours before I shut off the power bar. I thought I had invented a new power source! Then I came back to reality. The old hub does not have as much power output as the new one.


    by .5 hours do you mean half of an hour? thats insane, how could it be doing that. Quick, someone smart help. ;)

    Ok now im confused, which one is the working one?
  • profdlpprofdlp The Holy City Of Westlake, Ohio
    edited January 2006
    Turning the computer off doesn't kill the power to everything completely. Many motherboards even have a built-in light to remind you not to do something like change out RAM without killing the switch on the back of the PSU first. This feature is mostly useful for things like WOL (Wake-On-LAN) where you can turn a computer on remotely by requesting something across the network.

    As for the USB hub, if you go into Device Manager and look around under "Power" it will tell you how much each USB device is drawing, rated in mA.
  • godzilla525godzilla525 Western Pennsylvania Member
    edited January 2006
    frogdoctor wrote:
    Troubleshooting found the power backfeeding to the motherboard from the USB hub. Anyone come across this before?

    No. I'm not sure how the hub is able to send power back down the line to the PC and make it into the 5V standby line. It's possible there was enough residual charge stored in the PSU filter capacitors to hold it up long enough after you unplugged it until you managed to shut off the power to the hub.

    However, if something (the hub) has faulted, it's not out of the question for power to find it's way through the USB cable to the 5V standby line by means of the USB controller protection diodes—Many USB controllers are hooked into standby power to permit certain devices remain powered by instruction from the operating system (also found in Device Manager...Allow Windows to turn off this device to save power...) so that the system can be awakened by USB modem rings, keypresses, or mouse events.

    That's still... odd... though. :wtf:
  • frogdoctorfrogdoctor Toronto, On
    edited January 2006
    It took a while but I have found the power is coming from the APC hub.
    The old hub power source is 5V - 9VDC 2.6A - 1.8A. The new APC hub
    power source is 5.0VDC - 2.0A. The old one has more power (on paper anyway) than the new one.
    With the old hub, if I tell the software to shut down it does. My motherboard (ASUS) has a green LED on it to warn you power is still applied.
    No fans run when the system is shut down. If I disconnect the AC power cord from the PC power supply, the LED goes off.
    With the new hub, when I tell the software to shut down, it does, but the CPU cooler fan, and the case fan still operate. If I disconnect the AC cord from the PC power supply, the LED and the fans stay on, for as long as I keep the power to the hub. I even left it that way for 16 hours, it still was partially powered (the power supply fan does not run).
    I have changed cables from the motherboard USB port to the hub port, and this makes no difference. It is inside the hub itself, a difference in the designs of the two hubs. It seems newer, is not always better!

    FD
Sign In or Register to comment.