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K70B

Sensibly equivalent to:
PM22A
See also:
2 Volt Valves for Battery Receivers - Practical Class B Amplication
    
Extras ▼

 

The K70B from Every Ready is exactly Mullard PM22A, as Mullard made Ever Ready valves at this time.
The valve is a battery audio output valve for use in domestic broadcast receivers. The power output is low at 350 mW and so efficient loudspeakers were required to achieve an adequate listening volume.
For correct operation the anode load should be 19,000 ohms.
The gold paint is limited to the dome as audio valves do not need screening.
The pinch and lower mica. It is a true pentode with three wire grids.
Side view of the oval anode. The grid wires can just be seen at the lower end.
The classic envelope is 40 mm in diameter and, excluding the B5 base pins, is 92 mm tall.
References: Datasheet & 1043. Type K70B was first introduced in 1931.

 

Pin Connections
B5
1
2
3
4
5
a
g1
f(-)
f(+)
g2

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
ra
gm
Pout
D
2.0
0.15
135
135
-4.5
5.6
0.15M
2.2
0.34W
10%
PDF scanned from an original document held by the museum
Updated February 11, 2014.
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