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U18/20

Sensibly equivalent to:
4/100BU 45IU AU1 CV31 CV1264 FW4-500 FW4-800 NU12 RV200/600
    
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The U18/20 is a medium power full wave rectifier. We have two Marconi examples in the collection. This version is in a longer and narrower envelope than U18/20 but despite different anode construction and envelope size the electrodes are the same size.
To protect the cathode from damage the rectifier needs to be fed from a supply with an effective series resistance of 180 Ohms. The reservoir capacitor may have a maximum value of 16 μF
The classic envelope is 46 mm in diameter and, excluding the B4 base pins, is 124 mm tall.
References: Datasheet, 1040 & 1043. Type U18/20 was first introduced in 1939.

 

Pin Connections
B4
1
2
3
4
a(2)
a(1)
f
f

 

Absolute Maximum Operating Conditions
Rectifier
Vh
Ah
Va
mAa
4.0
2.8
500
275
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated February 26, 2013.
shape:classic construction:pinch type:rectifier.fw age:1930.1940 base:b4 heater:4.0v pins:4 pin:1.a(2) pin:2.a(1) pin:3.f pin:4.f
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