So I blew a fuse on my Mesa Dual Rectifier. I had 4 Mesa branded 6L6s and two 5U4Gs in it. I replaced the 5U4Gs with 2 brand new Mesa 5U4GBs and blew 2 more fuses. I have taken out the 6L6s and shaken them and nothing sounds broken. I can't even turn on the amp without the fuse blowing. I was told it might be a resistor problem. Does anyone have any insight? Thanks!