Thanks heaps Homepin,

So I would be best to replace this TIP122 all together?... Soldering is not a problem for me so I don't mind replacing it. (and will do a better job than whoever did it before)

I saw them on the jaycar site http://www.jaycar.com.au/productView.asp?ID=ZT2292 so if this is the one I'll head down there tomorrow and purchase.