Sensibly equivalent¶ to:
The 1FD9 is a diode pentode valve that was designed for battery portable radio receivers and is identical to the CV784.
This short grid base pentode was designed with particular reference to AF voltage amplification. The 1.4 Volt filament is to be run from a dry cell and the anode rating matches standard HT batteries.
The device was specified for use as a detector and first audio amplifier. 1040 gives the 1S5 as identical in all but name. The the most likely daye of introduction is 1951.
The MAZDA lettering. The three grid supports can be seen as can the top of the control grid winding.
The thin glass tube envelope measures 18 mm in diameter and the excluding the B7G base pins, is 48 mm tall.
References: Datasheet & 1040. Type 1FD9 was first introduced in 1947.
Absolute Maximum Operating Conditions¶
Updated April 07, 2015.