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U31

Sensibly equivalent to:
25Z4 CV3753
    
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The U31 half wave rectifier was designed for series heater use.
The maximum reservoir capacitor specified is 32 µF and the minimum effective series resistance has to be 100 Ohms.
The classic envelope is 42 mm in diameter, and excluding the IO base pins, is 99 mm tall.
References: Data-sheet, 1040 & 1043. Type U31 was first introduced in 1937. See also 1937 adverts.

 

Pin Connections
IO
1
2
3
4
5
6
7
8
ic
h
nc
nc
a
nc
h
k

 

Absolute Maximum Operating Conditions
Rectifier
Vh
Ah
Va
mAs
26
0.3
250
120
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 05, 2022.
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