I went to change my speaker cables today and had a problem tightening the speaker cable behind the 9B. I use spades so when I went to tighten the terminal the plastic part terminal was just turning making a grinding like sound but the terminal would not tighten on the spade. This only happened to 2 of them, the rest tightened up. Is something broken or stripped? I haven't changed my cable since I bought the amp 3 years ago. Any suggestions?
Tony