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MPT4

Sensibly equivalent to:
7A2 MP/Pen Pen4VA
See also:
Catkin Valves - The Metal Valve - Osram Catkin Advert
    
Extras ▼

 

The MPT4 is an output pentode made with an external anode. The design is known as a catkin - M-OV CAT valves were large cooled anode transmitting valves such as the CAM3 audio modulator.
One of the curious ironies of the MPT4 saga is that the catkin version of 1933 although a 'blind alley', was technically very superior to the glass version MPT4. Comparison of the two photos makes it quite clear that the large anode used in the glass version could not possibly be used in the catkin version and shows the benefit of the external anode design.
The two versions are, in fact, entirely different designs. The compact catkin version was possible because the external anode was directly air cooled and did not reflect excessive heat back to the cathode-grid region of the valve.
It took M-OV about five years to learn how to make large glass power pentodes with grid structures which did not emit electrons, or buckle, due to overheating.
See also MPT4 on a B7 base.
The screw connection to the screen grid on the side of the base. The copper anode is connected to the base via the wire held by the clip.
The side terminal used the same screw cap as the top caps of the early 1930s.
The catkin envelope is 18 mm in diameter and, excluding the B5 base pins, is 102 mm tall.
References: Data-sheet 1040 & 1005. Type MPT4 was first introduced in 1931.

 

Pin Connections
B5
1
2
3
4
5
st
a
g1
h
h
k,g3
g2

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
Pout
4.0
1.0
250
250
-13.0
32
-
-
3.0
3.2
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated August 23, 2020.
shape:catkin construction:pinch type:pentode age:1930.1940 base:b5 heater:4.0v pins:5 pin:1.a pin:2.g1 pin:3.h pin:4.h pin:5.k.g3 pin:st.g2
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