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PT4

Sensibly equivalent to:
42MP/Pen 7A3 A70C A70D AC/Z AC2/Pen APP4B CV1181 KT41 N41 Pen4VB PenA4
    
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The Osram PT4 is a directly heated output pentode that was introduced in 1931 and could be used in AC or DC mains sets.
The MPT4 would have a greater output and is indirectly heated.
The remains of the Osram brand label.
Looking up from the pinch.
Thanks to Mike Edwards for the pictures and information that this valve came from a 1932 Kolster Brandes KB321 wireless set.
The classic envelope is  mm in diameter, and excluding the B5 base pins is  mm tall.
References: Data-sheet, 1040 & 1043. Type PT4 was first introduced in 1931.

 

Pin Connections
B5
1
2
3
4
5
a
g1
f(-),g3
f(+)
g2

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
rk
rl
Pout
D
4.0
1.0
250
250
-16.0
32.5
7.0
42,000
2.85
420
7,500
2.0W
10%
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated October 06, 2020.
shape:classic construction:pinch type:pentode age:1930.1940 base:b5 heater:4.0v pins:5 pin:1.a pin:2.g1 pin:3.f(-).g3 pin:4.f(+) pin:5.g2
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