Removing the dustcap wil just give you a nice view of the magnet pole piece, but not anything you can fix.

Replacement lead out wires from the cone to terminals are available, but if you get no reading across the 'pips' the problem likely lies with the coils. Even checking that entails removing the cones. The foam surrounds will need prising off the chassis edge and the rear spider will need the same, if you can even reach it all round to do so.