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U142

Sensibly equivalent to:
311SU 31A3 UY41
    
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The U142 is a half wave rectifier designed for universal domestic equipment and replaced the UY21. By universal we mean AC or DC mains input and therefore no mains transformer. The national grid supplying 240 Volt 50 Hz Ac mains to all households eventually replaced the DC mains but in cost conscious equipment such as domestic radios and televisions the use of rectified mains without an isolating mains transformer continued for many years. Modern health and safety legislation would prevent this practice today.
The envelope shows that all four Type designations are equal. The way the hard glass base is formed looks typical Philips.
The anode has a X cross section and the working space is a small cylindrical space just larger than the cathode tube. The heater can be seen to be separate from the cathode connection.
Another view of the anode. The rippled effect in the glass is typical of late 1940's all glass valves with the B8A base.
The thin glass tube envelope is 20 mm in diameter, and excluding the B8A base pins is 60 mm tall.
References: Datasheet & 1040. Type U142 was first introduced in 1947.

 

Pin Connections
B8A
1
2
3
4
5
6
7
8
h
a
-
ic
ic
ic
k
h

 

Absolute Maximum Operating Conditions
Rectifier
Vh
Ah
Va
mAa
31.0
0.1
250
100
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated November 12, 2013.
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