The 6U5 = 6G5 is an American Magic Eye tuning indicator and its construction follows the normal pattern of a voltage amplifier triode feeding a display bowl. The electrode assembly is mounted centrally in the envelope.
The heater is wound as a double helix to minimise the external hum field. The anode of the triode connects to a flag electrode inserted into the display bowl.
Side view.
The cylindrical anode cavity and helical grid.
The central cap in the bowl hides the cathode within.
The wide glass tube envelope is 28 mm in diameter and, excluding the UX6 base pins, is 89 mm tall.
References: Data-sheet, 3002, 1043 & 1040. Type 6U5 was first introduced in 1937. See also1937 adverts.
