I turned on my Marshall 4140 today to let it warm up and when I went to switch the standby off....nothing. I checked all the connections and they were fine. Then I realized that the tubes weren't even glowing. I quickly switched receptacles to see if the outlet was the cause and...nothing! Checked the fuse and it seems to be fine. We were up and running yesterday without a problem. Any ideas? What could I have done wrong? I'm taking it in straight away tomorrow but I want to know what to expect. I'm crused.