Thread: USB Hub problem

It is possible that your external CD ROM actually requires an external power source even though the power connecter is a USB plug.

Does your CD ROM have two USB connectors? If so one is data and the other is power. You would need something like this to provide power http://www.amazon.com/Gilsson-Univer...4799502&sr=8-2

I hope this helps.

The external works fine If i plug it directly into the machine without the hub.

any other ideas?

You could be seeing a voltage drop on that run from the back to the front of the car. You may want to check the voltage at the hub.

If possible, take the hub and connect it to the power supply with a short cable and see if your CD works then. If so, you might need to get a point-of-load power supply.

i used a multimeter to check the voltage that was fine. but it wasnt able to check the amperage so i bought a new multimeter and im going to check that next.

i tested the amperage and it was drawing between 500ma and 1.2 amps, i think thats fine. should i just try to power the cd rom directly? or could it just not like a usb hub

I'd suggest you power the hub through its (separate) 5V connection.

The hub absorbs some power and may limit each port (current).
The usb spec is 500mA but maybe that means "at least"?. Hence the PC whatever might supply 500-1200mA.

Usually hi-current devices use 2:1 usb connector - ie, for a 1A device, 2 from the PC for 500mA each into one usb into the device.

ya but the power supply is able to supply 8amps on the 5v line i figured that should be plenty no?

8 Amps for a 1.2A load.... I suspect that is enough.

So either the hub is limiting port current, or the cable from the hub is too long...