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AP412LF

 
See also:
The Four Electrode Valve - The Bi-Grid Valve - A needless Invention? - Shortpath Construction
    
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The AP412LF is a bi-grid valve designed for audio. The Aneloy AP412 valves were the HF, P, RC, SC and U all were bi-grid valves.
Thanks to Richard Stibbons for donating this valve.
The LF designation is also present on the pinch as well as being etched into the envelope. The side contact is for the second grid.
The B4 Base has simple split pins. The side terminal is probably original.
The filament is broken. On the right of the anode are the two grids the inner is made of thinner wire. The construction style is close to that of the Cosmos Shortpath valves.
Both grids are fixed on one side only to thick wire supports.
A better view of the grids.
The balloon envelope is 35 mm in diameter, and excluding the B4 base pins is 98 mm tall.
Reference: 1043. Type AP412LF was first introduced in 1927.

 

Pin Connections
B4
1
2
3
4
sc
a
g1
f
f
g2

 

Absolute Maximum Operating Conditions
The Bi-Grid Valve
Vh
Ah
Va
Vs
Vg
ra
gm
4.0
0.12
20-50
10-15
-
11,000
0.68
Updated August 21, 2017.
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