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The Z719 is the M-OV version of the EF80 internally screened pentode. This RF valve design was the workhorse of VHF TV receivers and was introduced in mid 1950 to replace the EF91. It is a high slope RF pentode and not variable μ.

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.

Looking through the screening mesh the anode can be seen as two small plates strapped together at the centre. The suppressor grid can be seen as an open helix on strong copper supports. The inner grids are shaped so that the wire passes flat across the cathode. The control and screen grids are not aligned and the control grid has a much finer pitch.

The thin glass tube envelope is 20 mm diameter and excluding the B9A base pins, is 58 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type Z719 was first introduced in 1953. See also 1953 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.