I just picked up a clean D&A phantom triple stage amp. First of all I've read the tune up directions and cannot for the life of the amp get anymore than 200w from this thing. I've read on multiple sites that there is a grid tune on the back of the amp, well there is none..not even a spot for one. This is a tan/brown D&A, not sure if it's older/newer. I am driving it with my Cobra 2000 which i can dead key 2-4 watts and swings about 20w, yet the Phantom does not swing at all. Could it be bad tubes?