The EF80 internally screened pentode was a workhorse of the VHF TV receiver and was introduced in mid 1950 to replace the EF91. It was described as a high slope straight RF pentode. The EF85 was the variable μ counterpart to the EF80.The EF80 was much used for RF, intermediate frequency, and video amplification.The circuit designer is given maximum flexibility by having all electrodes brought to external pins. Many pentodes have g3, the suppressor grid, internally connected to the cathode.Through the outer screen the anode is a pair of plates joined by a strap. The suppressor and screen grids can be seen.BWB logo on the glass. Internally the anode strap is on the right inside the screen.The thin glass tube envelope is 20 mm diameter and excluding the B9A base pins, is 58 mm tall.References: Data-sheet & 1040. Type EF80 was first introduced in 1950. See also 1950 adverts. |