833A
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The 833A is a vacuum tube constructed for medium power radio frequency transmitter applications. It is a High-mu power triode intended for use as an RF power amplifier. It can also be used for audio amplification in a valve audio amplifier.[1][2]
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[edit] Specifications
The 833A is a large tube of the type sometimes known as a "cookie jar" tube,[3] with the envelope nominally measuring 116.8 mm (4.60 in.) in diameter and 219.2 mm (8.63 in.) in height. The 833A contains a thoriated tungsten filament designed to operate at 10 Volts and 10 Amps. A single tube could deliver 1000 watts of RF power while operating as a class C amplifier (forced air cooling required). A pair of tubes could be used as a modulator to deliver 2400 watts of AF power. The plate shows a dull red color when operating. [4]
[edit] Internal Construction
The tube is supported solely by its two filament posts. These posts are keyed with the F1 and F2 connection having a diameter of 9.5mm (0.375 in) and 11.1 mm (0.438 in) respectively.
[edit] Characteristics
Amplification factor, 35
Anode to Grid capacitance, 6.3pF
Anode to Filament capacitance, 8.5pF
Filament to Grid capacitance, 12.3pF
Values for two 833s working class B as an audio amplifier or modulator.
Va max, 3Kv
Ia max, 500mA (Averaged over one cycle of signal waveform per 833.)
Pin max, 1.125Kw (Averaged over one cycle of signal waveform per 833. This is the total input power to each 833 at maximum drive.)
Pa max, 300w (Averaged over one cycle of signal waveform per 833. This is the maximum anode dissipation and at this power level the anode reaches a temperature of about 800 degrees centigrade, and glows red hot.)
Vg1 max, -70v
A.F. grid to grid voltage, 400v Pk.
No signal D.C. anode current, 100mA
Max signal D.C. anode current, 750mA
Load resistance, (Per 833), 2.375K Ohms
Effective load resistance, (anode to anode), 9.5K Ohms
Max signal driving power, 20W avg.
Max output power, 1.65Kw avg.
Values per 833 working class B as an R.F. amplifier with a maximum modulation factor of 1.0.
Va max, 3Kv
Ia max, 400mA
Pin max, 450w (This is the total input power to each 833 at maximum drive.)
Pa max, 300w (This is the maximum anode dissipation and at this power level the anode reaches a temperature of about 800 degrees centigrade, and glows red hot.)
Vg1 max, -70v
Peak R.F. grid voltage, 90v.
D.C. anode current, 150mA
D.C. grid current, 2mA
Driving power, 10w appx.
Output power, 150w appx.
Values per 833 working class C as an R.F. amplifier with a maximum modulation factor of 1.0.
Va max, 2.5Kv
Ia max, 400mA
Pin max, 850w (This is the total input power to each 833 at maximum drive.)
Pa max, 200w (This is the maximum anode dissipation.)
Vg1 max, -500v, nom, -300v
Peak R.F. grid voltage, 460v.
D.C. anode current, 335mA
D.C. grid current, 75mA
Driving power, 30w appx.
Output power, 630w appx.
Values per 833 working class C as an R.F. amplifier or oscillator, (C.W. conditions, unmodulated, 50% Duty cycle.)
Va max, 3Kv
Ia max, 500mA
Pin max, 1.25Kw (This is the total input power to each 833 at maximum drive.)
Pa max, 300w (This is the maximum anode dissipation.)
Vg1 max, -500v, nom, -200v
Peak R.F. grid voltage, 360v.
D.C. anode current, 415mA
D.C. grid current, 55mA
Driving power, 20w appx.
Output power, 1Kw appx.
Grid voltages measured with respect to the mid=point of the directly heated cathode.
80% efficiency at A.F., dropping to 60% at 100MHz when used as an amplifier.[5]
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[edit] History
The 833A was preceded by the 833. [6]
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[edit] Applications
The 833A was widely used in small (1kW class) AM broadcast transmitters. Typically, a pair of 833As would be used in the final amplifier, plate modulated by another pair. It was also used in small induction heaters. This tube has also been used by hobbyists to construct a vacuum tube Tesla coil.[7]
[edit] See also
[edit] References
- ^ Frener, Michael. Wavac SH-833 monoblock power amplifier in Stereophile, July 2004.
- ^ Robinson, David. Wavac HE-833 amplifiers - The King of SET! in Positive Feedback Online, Issue 9.
- ^ Rosenberg, Harvey. Pathways to Power.
- ^ RCA Transmitting Tubes, TT5, 1962
- ^ R.C.A. Air-Cooled Transmitting Tubes, Technical Manual TT3, R.C.A. Manufacturing Company, Harrison, New Jersey, 1938
- ^ RCA Transmitting Rubes, TT3, 1938
- ^ Willis, Carl. 833-A Vacuum Tube Tesla Coil.
[edit] External links
- TDP Shortwave Transmitter Tubes. [1].
