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PT225

Sensibly equivalent to:
PM22
See also:
Lissen PT225 Advert
    
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The PT225 is a low power audio Pentode with a bright anode and a single inverted V filament. The load impedance should be 20,000 Ohms and the output is 250 mW.
In 1930 the PT225 battery output pentode was re-engineered onto a B5 base thus placing this exhibit at 1929. The base is brown mottled Bakelite.
The screen grid connects to the side terminal. The moulded terminal is original with tag.
The top components: mica support, filament tension spring, bright anode and the three wire grids.
This negative image reveals the Type designation and Lissen logo on the envelope dome.. The top wording is Made in England. The code number is 308.
The balloon envelope is 48 mm in diameter, and excluding the B4 base pins is 97 mm tall.
Reference: 1043. Type PT225 was first introduced in 1929.

 

Pin Connections
B4
1
2
3
4
tc
a
g1
f,g3
f
g2

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
gm
2.0
0.27
150
150
-6
6.0
1.5
1.4
Updated September 09, 2013.
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