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5B/255M

Sensibly equivalent to:
5B/252M CV391 CV8028
See also:
Beam Tetrodes and the 807 - Brimar 25P1 Amplifier - STC 5B/254M, 5B/255M, 5B/257/M & 5B/258M Advert - STC 5B/254M, 5B/255M, 5B/257/M & 5B/258M Advert
    
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The 5B/255M beam tetrode was designed for transmitter use in the HF and low VHF parts of the spectrum. The design has the same rating as the 807. The 5B/255M has a sister valve, the 5B/254M, that is a miniature enveloped version of the 807 complete with anode top cap.
In addition to RF power, the valves were designated for service as audio power amplifiers. Here the valve was to operate in class AB1 and a pair would deliver 15 Watts at 3% total distortion.
Looking along the grid axis, the side flanges are placed at the centre of the heat producing area for maximum cooling.
The wide glass tube envelope is 28 mm in diameter and, excluding the B8B base pins, is 79 mm tall.
References: 1040 & data-sheet Type 5B/255M was first introduced in 1957.

 

Pin Connections
B8B
1
2
3
4
5
6
7
8
h
a
g2
k,bp
g1
g1
k,bp
h

 

Absolute Maximum Operating Conditions
Beam Tetrode
Vh
Ah
Va
Vs
Vg
mAa
mAs
mAg
Pdriv
Pout
Pdiss
freq
6.3
0.9
600
250
-45
100
8
4
0.3W
40W
25W
60
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated October 20, 2020.
shape:wide.glass.tube construction:all.glass type:beam.tetrode age:1950.1960 base:b8b heater:6.3v pins:8 pin:1.h pin:2.a pin:3.g2 pin:4.k.bp pin:5.g1 pin:6.g1 pin:7.k.bp pin:8.h
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