GZ34STR TAD selected rectifier tube (RT501) GZ34CZ TAD selected rectifier tube (RT521) 5Y3GT TAD selected rectifier tube (RT503) 5Y3WGTB TAD selected rectifier tube (RT513) 5U4GB TAD selected rectifier tube (RT504) 5U4G TAD selected rectifier tube (RT512) EZ81/6CA4 TAD selected rectifier tube (RT506) SSR1 TAD solid state rectifier (RT515)