The 6BA6/EF93 is a miniature screened pentode on a B7G base. It is a variable μ valve designed for HF use.
The yellow paint was initially used for a year to mark 50 years of Mullard - 1969-70. However, some 1975 production at Blackburn also used yellow paint after a drum was found in the stores.
The circular hole in the anode end wall shows the ends of the grids and the copper supports.
A close-up of the suppressor wire being gripped in a notch in the support. A pointed knife disc pushes the copper aside, the wire is wound into the notch and a final roller closes the displaced copper over the wire.
Control and suppressor grids are on copper supports.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
References: Data-sheet, 3002 & 1040. Type 6BA6 was first introduced in 1950. See also1950 adverts.
