The VR is the Philips/Mullard/Valvo code for a E188CC or a 7308 tube. The 5 after the VR denotes the fifth variation of that tube. The "*" is for Hicksville, NY, whereas the delta A would be Heerlen, Holland. The '5' after that would probably be 1965, as this tube wasn't made in the 50s and I don't think Hicksville was making them in '75, but this is a close one. If it has white labeling and given the fact that it's a CEP marked tube, I'm 95% sure it's 1965. And finally, the B is for February.
So we have US made Amperex 7308s, which are fifth versions and are consistent with a Feb. '65 manufacture date.
Simple, no?
Now whether the tubes test strong, are well matched across the triodes and are not mircophonic, I can't say. Plug 'em in and see.
Take care, Chris
So we have US made Amperex 7308s, which are fifth versions and are consistent with a Feb. '65 manufacture date.
Simple, no?
Now whether the tubes test strong, are well matched across the triodes and are not mircophonic, I can't say. Plug 'em in and see.
Take care, Chris