FU-33 Vacuum Tube Amplifier 833A 833C DIY
The FU33 electron tube is a direct-heating thorium carbide cathode glass triode, the anode cooling method is natural cooling, the maximum anode dissipation power is 350W, the maximum operating frequency is 30MHz, and the output power is 1000W. It is mainly used for oscillation in industrial high-frequency heating equipment and amplification in radio equipment.
This tube can be used interchangeably with the 833A/C type electron tube produced in the United States.
Vacuum tube FU33 is a high-power triode, usually used in communication equipment, with the characteristics of high voltage resistance. Some data of FU33 are indeed very scary. For example, the maximum anode voltage can reach thousands of volts, the maximum anode dissipation power is about 300W, and the filament current can reach 10A, which is very harsh on power supply. It seems that using FU33 to make power amplifiers is not an easy thing, but why use it? A senior audiophile said, "This vacuum tube has good pressure resistance, good sound, strong three-dimensional sound field, strong dynamic output of Class A, and freely retractable."
The DIY project spent a lots of efforts from at least 6 months ago, and now finally finished.
Here, we attached some data of vacuum tube FU-33 for you information.
Basic Parameters
Filament Voltage ……………………………………………… 10 V
Filament Current ……………………………………………… 9.4---10.6A
Inter electrode Capacitance
Grid Plate …………………………………………………… 5.5--7.1 pF
Grid Cathode ………………………………………………… 10.1—14.5 pF
Cathode Plate ………………………………………………… 6.4—10.6 pF
Amplification factor……………………………………………… 31.5-38.5
Operation Frequency …………………………………… 30MHz
Anode DC Voltage…………………………………………… 3kv
Anode DC Current ……………………………………………… 415Ma
Grid Current ……………………………………………… 40-70mA
Grid Impedance ………………………………………… 3.5/5 kΩ
Output power ……………………………………………… 1000W
Application ……………………………………………… broadcast communicate and High- frequency hearting.
Cooled style …………………………………………… wind cooled
Limit using parameter
Maximum filament voltage: 10.5V
Minimum filament voltage: 9.5V
Maximum anode DC voltage: 3300V
Maximum anode power dissipation: 350W
Maximum grid power dissipation: 20W
Mechanical Parameter
Weight: (approximately) 0.6Kg
Installation method: vertical, anode lead up
Cooling method: natural cooling
The highest temperature of the shell: 225℃
The highest temperature at the sealing joint: 200℃
High temperature at the terminal: 200℃
Use requirements and precautions
1. When using electronic tubes, there should be no more than one limit value parameter. Exceeding the limit value is not allowed even for a very short time.
2. The lead wires connected to the electrode of the electron tube must be in good contact with the electrode, otherwise an arc will be generated, and the electrode will be melted through, causing the tube to leak.
3. The electronic tube should be handled with care during packaging, storage, transportation, and replacement to avoid damage.
4. When the electron tube is working, the ventilation should be good, the surface temperature of the electron tube should not exceed 145 degrees Celsius, otherwise, the glass bulb should be blown to cool.
5. Note: When the anode dissipation power is greater than 300W, the glass bulb is blown and cooled.
Applications
More details for vacuum tube FU33 (813A/813C), please find here.
