I assembled my first kit last weekend and I made a mistake in soldering the end of an ofc (oxygen-free copper) wire to the terminal of a tweeter without first sliding the heat shrink up the wire. Now it's all soldered together and I can't get the heat shrink on the wire (since the other end of the wire is also soldered to the rest of the cross-over network). Any suggestions? Would wrapping electric tape around the exposed lead do just as well? Or is there a kind of heatshrink that can be wrapped around after things have been soldered together? I tried to unsolder the joint, but after 2 minutes, the solder still wasn't getting hot enough to let the joint loose. My solder gun is pretty weak though. Actually, how bad is it to leave it exposed to the air?