do you hear any noice at all? if you cant even hear background hiss that the amp may usualy produce give it to a tech to check out, if you dont know what your doing with valve amps you can easily get worse than a small shock. if you can hear background hiss check the rest of your signal chain, start by removing any pedals and go direct to the amp, try this with al your cables. if this works with all your cables add your pedals one by one finding the one that may be causing the problem. if you stil have no sound either try another guitar going into your amp or the same guitar going into another amp to see if its the wirring in your guitar