If you can't hear a difference:
unscrew the screws that are holding your electronics control back plate.....and take a look at your caps to see if any of the two wires that are connected to the pot and cap are broken. In your case.....you will look at the cap that is attached to your volume knob's lugs on the pot.......I had this problem when i got a Js1. One of the wires that connected to a lug on the pot was broken and i had to replace it.
If no wires are unconnected or broken, and you still can't hear a difference.....maybe it's time to put a new one in.....
Your local guitar tech would do it for you. but if you know how to solder...you can do it yourself. Of course you'd have to buy the 330 uf capacitor from an ibanez dealer......check with your local music guitar tech....he may have one in stock.