HELLO, I HAVE A T-4X THAT HAS IDLING CURRENT BUT NO DRIVE OR OUTPUT. I HAVE CHECKED ALL TUBES,FOUND THE DRIVER TO BE BAD REPLACED WITH A 12BV7 MY TUBE BOOK SHOWS IT TO BE A DIRECT REPLACEMENT FOR THE 12BY7. STILL HAVE THE SAME NO DRIVE OR OUTPUT. CAN SOMEONE GIVE ME SOME IDEAS. TNX TERRY W9CAU