This exhibit is a standard EF80 made in Poland by Polam.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.
In this image the screen grid wire can be seen to pass flat across the inner grid and cathode. The suppressor grid is an open pitch wire helix.
The shaped outer screen is held between the mica discs.The thin glass tube envelope is 21 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. |
