I have a 6BK4 Tube used for HV regulator. What symtoms does tube give when bad?? Is there a differance between a 6BK4A/B tube & a 6BK4C tube?? My tube tester doesn't test these, what tube checker does???


:dunno:

Dark smeary picture. Blooms easily. Width bounces allover the place. Look at your tube. Is it dark brown in color on the glass?