The 17JN6 is a Compactron beam tetrode designed for line output use. The 6JN6 has a 6.3 Volt heater and the 12JN6 has a 12.6 Volt heater but otherwise are identical to the 17JN6 electrically. This whole series is electrically identical to the 6JM6 with the exception of a slightly lower capacitance between the control grid and anode.
The positive peak anode voltage can be as high as 6,500 Volts but the DC supply would normally be a maximum of 770 Volts. With a 17.5 Watt anode dissipation this would make a useful Class C RF amplifier for the HF bands.
The working part of the anode in the centre with side flanges for greater heat dissipation.
The B12C or Duodecar base.
The wide glass tube envelope is 38 mm in diameter, and excluding the B9A base pins is 62 mm tall.
Reference: Datasheet. Type 17JN6 was first introduced in 1964.