I am prepping my Hartke 210 Combo ("Transient Attack" c. 1993) for possible sale. There are two issues regarding the drivers I could use some help on. 1) Is there any way to safely clean them? One of them has brown spots on it and I'm not sure if something got spilled on it or if it's rust (is that possible on aluminum), or what. The driver sounds great, it just looks bad. 2) The other driver, appears to either be blown or suffering from the notorious "loose dust cap" issue. In the worst case scenario of having to replace the driver, do I have options other than buying one new from Samson (i.e. is there someplace that deals in reconditioned drivers), and what can I expect to spend (or need to discount my asking price if the buyer will take it as-is)? Thanks in advance.