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IW4-350

Sensibly equivalent to:
A11D R2 UU4
    
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The exhibit above looks like a late (1960s) version of the IW4-350 but the initial letter is indistinct. This is an indirectly-heated 4V AC HT rectifier essentially equivalent to the MU12 and UU4.
This full wave rectifier features indirectly heated cathodes that are tied to one side of the heater.
The cathodes can be seen to be flattened ovals and the white oxide coating is visible through the holes in the anodes.
A closer view of one anode.
The lower mica components.
The classic envelope is 40 mm in diameter and, excluding the B4 base pins, is 104 mm tall.
References: Data-sheet, Private communication & 1043. Type IW4-350 was first introduced in 1936. See also 1936 adverts.

 

Pin Connections
B4
1
2
3
4
a(1)
a(2)
h,k
h

 

Absolute Maximum Operating Conditions
Rectifier
Vh
Ah
Va
mAa
4.0
2.0
350
120
Thanks to Andy Cowley for supplying the above PDF datasheet.
Updated March 17, 2014.
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