In the late 1970s and early 1980s, due to the limitations of the technical level at that time, most of the final launch tubes of machines above 50W used metal ceramic tubes. In order to ensure its linearity and bandwidth, it is required to make the distance between the grid and cathode of the TV launch tube very small. In this way, the high temperature of the cathode is likely to cause the impact pole to make the electron tube fail. Therefore, the process requirements of metal-ceramic electron tubes are high, the relative cost is large, and the service life is short. The price of each electron tube is several thousand yuan, which is not a small burden for stations using TV transmitters. How to extend the service life of the TV transmitter tube, each station is exploring and has gained a lot of experience. Now the measures taken by Hami TV are introduced as follows. (1) Regular maintenance of metal ceramic tube. First of all, it is necessary to ensure that there is sufficient air volume to cool the pipe, and the air inlet filter of the fan must be cleaned frequently to keep the tank box clean and sealed. The stock tubes must be powered on every six months, preferably by rotation, and the tubes should be refined. When the transmitter is powered on, it is necessary to preheat the electron tube. Generally, the high voltage can be applied after 10 minutes of preheating, but in actual use, the 10 minute time is still short. We use manual power-on, generally warming up for 30 minutes in winter and 25 minutes in summer. When the power is off, the high voltage is applied. After turning off the filament power, the air must be blown for at least another 30 minutes. (2) The temperature of the cathode of the electron tube is mainly determined by the filament voltage. The resistance value of the filament is the thermal resistance value designed according to the cathode temperature during normal operation. The cold filament resistance is generally only about 1/10 of that of the hot filament when it is just turned on. The original machine filament power supply adopts constant voltage power supply, so that there will be greater thermal shock and electrical shock when starting up, which will cause pincushion distortion of the tube-shaped cylindrical filament of the tube, and it is easy to cause the grid and the cathode to collide (working area Only 15mm), damage the tube. Now we have installed a filament voltage control device. The filament voltage of the device gradually rises in a smooth curve at startup, and reaches the rated voltage value in about 2 minutes. Therefore, the device can control the filament voltage of the final tube of the TV transmitter, which is effective To solve the problem of the impact of the filament, it can extend the service life of the tube. (3) The life of the electron tube is determined by the ability of the cathode to emit electrons. The electron emission capability of the cathode of the tube is a function of the cathode heating time t and the thermal temperature T. Under the same heating time t, its life depends on the operating temperature, and the operating temperature is determined by the filament voltage. Therefore, the level of the filament voltage It is the key to determine the service life of the tube. As long as the tube filament is coupled with the rated working voltage to make the cathode heat and emit electrons, the service life of the tube will be consumed. According to calculations, the life of the cathode is shortened by about 50% every time the working temperature of the cathode is increased by 20-25 ° C. Properly reducing the filament voltage and lowering its working temperature is one of the measures to extend the service life of the electron tube. In actual use, the filament voltage of FC-732 can be reduced to 10.3V (107V at the factory) without affecting its transmit power. (4) Strictly control the cathode current of the static working of the electron tube. For a single channel 1kW TV transmitter, the static cathode current of the tube FC-732F is adjusted from the original 0.5A to 0.3A. Since the tube works in Class A and B, it can reach 0.7A when it is dynamic, without any impact on the overall machine index. The board consumption is reduced, and the working temperature of the electron tube is relatively reduced. (5) When the machine is working, the power shall not be cut off at will to ensure the air cooling of the electronic tube. In this way, a set of automatic switching uninterruptible power supply (UPS) needs to be added to the transmitter fan, and the 3kW UPS power supply can meet the requirements. (6) To keep the outside of the tube clean and improve the heat dissipation effect, for the new tube to be installed on the machine, the installer should wear cotton gloves and scrub the tube with absolute ethanol, and carefully put it into the tank. (7) Observe and record the working data of the electronic tube at any time. If it is found that the cathode current increases and the curtain grid current is abnormal, it should be checked immediately. It is strictly forbidden to work the electron tube under self-excitation to prevent machine detuning and high-frequency ignition. (8) Maintain the proper temperature of the transmitter room. When the temperature in summer is particularly high, ensure the reliable operation of the air conditioner. The temperature of the fan room must not exceed 25 # to provide the best air temperature and air volume for the electronic tube. Through the above use of electron tubes, the number of electron tubes used by the six television transmitters of Hami TV in the past two years has been reduced from 4 to 5 per year to 1 to 2 per year, which extends the service life of the tube by 2 to 3 times. , Not only to ensure high-quality and safe broadcast, but also save the maintenance costs for Taili, and achieved good social and economic benefits. Deep Fryer,Deep Fat Fryer,Deep Fryer Machine,Visible Window Deep Fryer Visible Shaoxing Haoda Electrical Appliance Co.,Ltd , https://www.hotplates.nl