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WE252A

Sensibly equivalent to:
252A
    
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The Western Electric is a directly heated medium power audio output triode. It is also probably the most sought after NOS audio valve. These are very rare in 2021 and a single valve can sell for £3,000.00.
In a single ended configuration a single valve can produce about 7.0 Watts.
The WE252A was superseded by the 275A. The 275A has a maximum anode voltage of 300 Volts and was designed for a three Watt output.
The anode dissipation is 27 Watts. The blackened rectangular anode is held at all four corners and the supports fitted to a collar that is tightened around the pinch stem. The PX25 has a similar construction and an anode dissipation of 25 Watts.
The base is of the bayonet type and a locating pip is present to engage in the slotted base.
The filament is an M shape and made of oxide coated ribbon. The top of each loop is held by a tensioning spring. In view of the anode voltages involved the springs are fixed into a ceramic block that fixes to the tops of the anode supports. Notches in the side hold the tops of the grid supports. The anode is blackened and the thin nickel sheet is ribbed for dimensional stability.
The top ceramic block with the focus on the tensioning springs.
The base of the anode showing the filament fixings and the central support hook. The filament tape is welded to the support rods. Clearly the tape is not tungsten but probably molybdenum.
The base with locating pip. The fixing of the collar around the pinch stem is clear to see.
The type designation pressed into the base cap.
The WE252A is presented here only because it was lent to the museum for photographing.
The balloon envelope is 66 mm in diameter and, excluding the UX4 base pins, is 145 mm tall.
References: Data-sheet. Type WE252A was first introduced in 1936.

 

Pin Connections
UX4
1
2
3
4
a
g1
f
f

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
Vg
mAa
ra
gm
5.0
2.0
450
-65
43
1,700
3.4
PDF scanned from an original document held by the museum
Updated September 02, 2021.
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