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1FD9

Sensibly equivalent to:
1S5 CV784 DAF91 ZD17
See also:
CV784 short entry
    
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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.

 

Pin Connections
B7G
1
2
3
4
5
6
7
f-
nc
a(d)
g2
a
g1
f+

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
1.4
0.05
67.5
67.5
0
1.6
0.4
0.6M
0.63
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated April 07, 2015.
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