I did a search read some threads, not finding answers... So I just purchased my svt from tber. The amp is about 4 and half years old mint condition, never had a tube change because it never gave him a problem. The bias 2 was glowing red. I figured it needed a new set of power tubes. Tech called back said it was the case and he would have to change all six because the ampeg runs in an aaa bbb setup. cost 325. Heres my questions. Do they really need to change all six and should I ask for all the still working tubes back. I think only 1 was giving a problem. Is Jimmy in da house?