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A tungsten filament acting as a directly heated cathode in a low pressure mercury gas discharge lamp which emits electrons. To increase electron emiss
A tungsten filament acting as a directly heated cathode in a low pressure mercury gas discharge lamp which emits electrons. To increase electron emission, a white thermionic emission mix coating is applied on hot cathodes, visible on the central portion of the coil. Typically made of a mixture of barium, strontium, and calcium oxides, the coating is sputtered away through normal use, eventually resulting in lamp failure.
Two indirectly heated cathodes (orange heater strip) in ECC83 dual triode tube
Two indirectly heated cathodes (orange heater strip) in ECC83 dual triode tube
Glow of a directly heated cathode in an Eimac 4-1000A 1 kW power tetrode tube in a radio transmitter. Directly heated cathodes operate at higher tempe
Glow of a directly heated cathode in an Eimac 4-1000A 1 kW power tetrode tube in a radio transmitter. Directly heated cathodes operate at higher temperatures and produce a brighter glow. The cathode is behind the other tube elements and not directly visible.
SEM Image of G1 Support and G1 Wire, of a heavily used Pentode showing Barium oxide Contamination (green) from the cathode.
SEM Image of G1 Support and G1 Wire, of a heavily used Pentode showing Barium oxide Contamination (green) from the cathode.
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Later thermionic vacuum tubes, mostly miniature style, some with top cap connections for higher voltages
Later thermionic vacuum tubes, mostly miniature style, some with top cap connections for higher voltages
Hot tubes in an audio power amplifier, emitting their distinctive red-orange glow
Hot tubes in an audio power amplifier, emitting their distinctive red-orange glow
Illustration representing a primitive triode vacuum tube and the polarities of the typical DC operating potentials. Not shown are the impedances (resi
Illustration representing a primitive triode vacuum tube and the polarities of the typical DC operating potentials. Not shown are the impedances (resistors or inductors) that would be included in series with the C and B voltage sources.
Radio station signal generator with vacuum tubes
Radio station signal generator with vacuum tubes