Precautions for using electron tubes

(1) The electron tube should be used under the condition of rated filament voltage.
(2) The power loss of each electrode of the electron tube shall not exceed the limit value.
(3) Try to avoid using filament series circuit. If it cannot be avoided, the current characteristics of the filaments should be the same to prevent uneven heating of each cathode.
(4) The electron tube is activated, aged and tested before leaving the factory. Mechanical and electrical aging of the electron tube is not allowed after leaving the factory, but its electrical performance and parameters are allowed to be tested.
(5) When using a side-heated electron tube, the potential difference between the cathode and the filament cannot exceed the specified limit value. For this reason, a special filament transformer is often used for power supply. In order to eliminate the influence of unstable leakage current, a shunt resistor of about several ohms can be connected between the cathode and the filament without hindering the operation of the circuit.
(6) It is very important to correctly select the first grid circuit resistor. This resistor should be as small as possible, especially for high transconductance electron tubes.
Usually, it is better to use self-bias instead of fixed bias circuit. For electron tubes with high transconductance (greater than 10 mA/V), a resistor with a larger resistance than the normal bias can be connected to the cathode circuit. However, it should be noted that the cathode potential is high at this time. In order to ensure the required negative gate bias, a positive voltage lower than the cathode potential must be supplied to the gate so that the gate voltage is negative to the cathode.
(7) Although the electron tube can still work normally when used under extreme parameter conditions, its life will be rapidly shortened. It is not allowed to use the electron tube under extreme parameter conditions.
(8) The receiving amplifier tube is still stable when working in high temperature (+70°), low temperature (-55°), and high humidity (relative humidity up to 98%, temperature 40±2°).
(9) When the ambient temperature rises, the working stability of the electron tube depends on the temperature of the most heated part of the tube shell. The temperature of the tube shell is determined by the heat radiation, heat conduction, convection and heat dissipation area of ​​the electron tube, as well as the temperature of the objects around the electron tube. Therefore, when designing electronic devices, the following should be considered:
① When using a shielding cover, it should be ensured that the tube shell can conduct heat away through the action of air, and the heat reflection on the surface of the shielding cover should be small (for example, a black shielding cover).
② The position arrangement of each component in the device should be conducive to the heat dissipation of the electron tube.
③ To control the tube shell temperature of the electron tube, the allowable temperature of the glass shell of various electron tubes is different. For example, the allowable limit temperature of the power output tube during operation is generally not more than 90°C.
(10) Except for high-reliability electron tubes with special structures that can work under higher acceleration, other receiving and amplifier tubes can only withstand small vibrations for a short time. Therefore, attention should be paid to the shock absorption of the electron tube when using it.
(11) When using small tubes (thumb-type) and other electron tubes without tube bases (but with tube pins), the following conditions must be observed in order to prevent the glass shell from being broken or damaged:
① Use the tube socket specified by the Ministry of Electronics Industry.
② When inserting the electron tube, the normal position of the contact spring in the tube socket hole should be prevented from being damaged.
③ Avoid using the empty pins of the tube socket as connecting solder pieces.
④ When plugging and unplugging the electron tube, the direction should be perpendicular to the plane of the tube socket.