Haltron EF183 frame-grid variable-mu RF pentode
The EF183 is a high gain variable μ RF amplifier pentode. It is a late 1950s design and superseded the EF85. The EF184 was the straight version of the design and replaced the EF80. All four valves have the same pin connections. In 1959 Mullard describe the EF183 as a frame-grid variable-mu RF pentode for use as an automatic gain-controlled IF amplifier in television receivers. The heater is suitable for series or parallel operation by AC or DC. The valve performance figures are given at 40 MHz and the normal TV IF frequency was around 33 MHz. The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 54 mm tall. The EF183 was first introduced in 1959.