PX25M-GL Datasheet

The AVVT PX25 is only available with mesh plates.   This tube is an exact replacement for the original Marconi PX25. 


  • AVVT's patented ribbon filaments with 16 flat Surfaces
  • Mesh plates
  • Ceramic tube base,  with nickel plated brass sides. 
  • Globe Glass bulb 
  • Extra large getters, flashing the complete tube bottem. 
  • Unbreakable hard-metal filaments. (Note2

Plate Detail
Click here for plate curves

PX25 Filament Ratings
Filament Voltage 
4 Volt  (AC or DC 
Filament Current 
2.2 Ampere 
PX25 Maximum Conditions See also Note 3
Plate Voltage 
Plate Current 
Plate Dissipation 
Power Output in Class A 
PX25 Typical Data
Plate Voltage 
Plate Dissipation 
Plate Current 
Grid Voltage 
Plate Impedance 
1140 Ohm 
Amplification Factor 
7,8 mA/V 
Load Impedance 
3000 - 5500Ohm 
Grid Resistor
max. 50k Ohm
Operating Lifetime 
40.000 hours 
PX25 Mechanical Data 
Size 190 x 60mm
(Includes tube base) 
145 Gram 

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Note 1) Open Filaments means, the filaments and the grid are longer than the Plate, and stick out on both ends for about 5...8mm. The cold ends of the filaments do not have a very good function, and cause distortion. The AD100 does not use this part of the tube, and the emitted electrons by the cold ends, will bypass the Plate, and land on the glass. At maximum Power this may cause fluorescent, blue glow on the tube glass inside. See also our Tech Brief on Blue Glow in Tubes.
Note 2) Hard-metal filaments are operated at much higher temperature than normal tubes. This tube will glow bright orange, instead of the dark orange color of nickel filament tubes.
Note 3 Individual Test data, such as: Matching Data, Grid Current, Vacuum, Filament Current, etc, are on the Certificate that comes with each individual Tube. Each tube is numbered, inside the bulb with a metal Tag

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