I just replaced the tubes in my Ten Tec Centurion with new matched pair RF Parts 3-500ZGs and have (1) from the old set FOR SALE. Before one of the tubes shorted - blowing one of the AC line fuses, the amp put out full power, so this is a good tube. New: $189.95 http://www.rfparts.com/tubetran.html Sale Price: $ 100.00 73, Bruce - N1LN