Hi, my carlsbro amp head arrived this morning, but it doesn't seem to be working. The 4 valves were packed seperately inside the case, so i 'installed' them, and took it over to my freinds house, where my cab was. The ohm rating of my cab is 8 ohms, and the closest setting on the amp was 7.75, so i used that. The mains settings on the amp are 110, 225 and 250, so i used 250. When i switched it on, the pilot light lit up which was encouraging, but... When i played the amp made strange noises, a kind of rattling, appartently my friend could see the valves blinking. Has anybody got any idea what's wrong with it? please help me if you can, im very sad.