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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 an output pentode that was introduced in 1931. It gives less output than the MPT4 but is for use where the indirectly heated valve cannot be used.
This exhibit has the original balloon envelope. Later production moved to the shouldered or classic envelope.
The box anode is substantial and held by rods in each corner. The rods extend down to a clamp around the pinch stem.
The production is inbetween the use of the glass rod for insulated supports and mica sheets. Here both are employed.
The filament can be seen to be oxide coated and held in hooks attached to spring arms that themselves are fixed into the glass rod.
The pinch end. The control grid and suppressor grids are visible but the screen grid is difficult to see. The U support at the base of g3 is mirrored by a similar U shaped support for g2 seen beside it.
The balloon envelope is 65 mm in diameter, and excluding the B5 base pins is 142 mm tall.
References: Datasheet, 1043 & 1040. 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 July 01, 2017.
shape:balloon 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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