The 6064 is a special quality version of the EF91. The special quality valve has a more rugged build than the commercial EF91 and a guaranteed minimum number of hours service life if used under specified conditions, such as bulb temperature etc.
Brimar special quality valves, eg 6064, originally had a paper label with the letter T to indicate their Trustworthy range. When special quality valves were normal the T was dropped.
The top mica is duplicated and the extra strength prevents early movement of the electrodes when used in an environment subject to vibration such as vehicles and aircraft.
The three wire grids and copper supports for the control grid. The suppressor grid has a closer pitch than expected and so could be used as a control electrode.
The anode is two small plates joined by an integral strap.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
Reference: Data-sheet. Type 6064 was first introduced in 1951. See also1951 adverts.
