Thanks guys, very detailed--I appreciate it. Will give it a try this weekend when I have some time and let you know.

  This is my first post. Glad I found you guys.  Been playing guitars for almost 35 yrs. now and have learned a bit over time about how to keep things working. Being left handed I have had to modify a few guitars (SGs mostly) for southpaw playing. Very little amp work though--made a few speaker cabs. Still playing but I let a couple of my older, bigger amps sit around for about ten years. Well now my son is heavily into it and the old amps are dirty, scratchy, one fades in and out a little bit. One is a tube marshall copy-handmade by a friend of a friend of a friend about 40 years ago. The other is a fender scorpio-a solid state made in 1970--like a twin. Would like to dig a little deeper into this whole field but, for now, I think a simple cleaning is all these amps need and a good way for me and the boy to start. What should I do?