unreliable USB port

[Sebastian42]

I want switchable access to an external HDD, and have bought (from Ebay) and set up, a number of powered hubs - a number, because I found that 'contact was lost' after a short period of 'normal' functioning, and so replaced the hubs with new ones. After much trial and error (over years) I have discovered reliable operation is achieved only by removing the HDD USB cable from the hub socket and then re-inserting it - or simulating that action by moving the connector in the socket without actually extracting the USB plug. The need to 'remove & replace' the plug in the socket, pretty well defeats the purpose of having a switchable hub socket.  I would like to know why proper functioning stops after a short period of use when the hub is new; and why 'rubbing the plug in the socket' restores function; and if there is a technique (greasing the socket with graphite powder ?) to make it reliable.

[Salmon Trout]

Please clarify - same plug, different sockets?

[Geek-9pm]

After much trial and error (over years) I have discovered reliable operation is achieved only by removing the HDD USB cable from the hub socket and then re-inserting it - or simulating that action by moving the connector in the socket without actually extracting the USB plug.

This is a typical symptom of marginal hardware.   

[Sebastian42]

Same plug, same socket - removal not even needed, just 'jiggling' the plug in the socket brings recognition of the HDD.

[Salmon Trout]

I was trying to establish if the problem recurs if you insert the same plug in a different socket (I presume whatever device you are connecting to has more than one USB socket?).

If the problem moves to a new socket, it is likely that the USB lead you are using has a faulty connector. If the lead is detachable at both ends, try a new one - you can buy them. If it is captive to the external drive, then you have a problem, that may be solved by purchasing a new empty enclosure, and opening up the faulty one and transferring the hard drive.

If the problem goes away when you move to a new socket, then it is likely that you have a damaged or marginal socket.