The products can provide various specifications of rectifier bridge devices according to customer requirements. The electrical properties, appearance, reliability, safety indicators and environmental protection indicators of the products all meet the relevant standards.
Planar Die Construction Sealed Glass Case Ideally Suited for Automated Insertion - 75V Nominal Zener Voltages
MINI MELF,Smd mini melf,zener mini melf,mini melf package,mini melf resistor,mini melf diode,mini melf resistor datasheet Changzhou Changyuan Electronic Co., Ltd. , https://www.changyuanelectronic.com
The aging of the power tube by the segmented filament power supply treatment method means that its electron emission force is reduced to the minimum requirement of the design. At this time, the required screen flow cannot be obtained by adjusting the bias voltage. Basically, the tube is difficult to Working on the original amplifier, barely using it can only achieve a fading effect. If the tube used is very rare and of great value, a method that is slightly troublesome but can greatly extend the working period of the tube is worth considering. This method is called the segmented filament power supply treatment method.
The segmented filament power supply treatment method is actually to control the temperature of the filament (cathode) so that it can maintain a certain emission power for a long period of time. As shown in Figure 1, when a new set of tubes is equipped with an amplifier, the first 200 hours of operation is to adjust the filament voltage to a specific filament voltage of the tube (100%), for example, kt88 is 6.3v or 300b is 5v. The function is to make the tube have enough temperature, so that the gas ring getter collects the residual gas left in the material during the manufacturing process. After 200 working hours, the tube has basically stabilized, and the filament power supply is adjusted to a value of 95%, that is, from 6.3v to 5.9v or 5v to 4.75v. A lot of actual data proves that the working period of the tube will be increased by 2.2 times at 100% filament voltage, that is, the tube with a life of 100,000 hours will become 220,000 hours. Until the tube cannot provide the minimum required screen flow, the filament power supply is adjusted back to 100%, that is, 6.3v or 5v. The filament voltage is high, the screen flow will rise due to the strong emission power, and the tube can work for another period of time. Then the screen flow drops again. At this time, increase the filament voltage by 0.5%, that is, adjust it to 6.7v or 5.25v to increase the filament temperature, the tube's emission power will increase again for a short period of time before it drops back, and then the tube is successful. Basically, the working life of a tube adopting this method of adjusting the filament voltage in stages will be increased by as much as 3 times that of a tube using the correct filament voltage (6.3v), that is, from 100,000 hours to 300,000 Hours, this is the conclusion drawn after a lot of practical operation experience, many radio stations use this method.
The filament voltage has a great influence on the emission capacity of the direct heating tube. The allowable voltage range of a 6.3v tube is only between 5.8v and 6.7v. When it is working with a 6.7v filament for a long time, it has a life of 100,000 hours. It will be reduced to about 60,000 hours, which is due to the fact that the launching force is too active to accelerate the aging of the cathode. Some people think that Guan Zi's voice is full of strength at this time, although it is worth it at the cost of short life, this is a matter of opinion. Conversely, if the filament supply voltage is too low, it will also cause big problems. For example, when the filament voltage drops to 5.35v, a new tube that can normally work for 100,000 hours will be shortened to only 20,000 hours. The reason is Insufficient temperature in the tube will cause a large amount of residual gas in each structural material in the tube to be released, some of which will attach to the surface of the cathode, and the place where the residual gas adheres on the cathode surface will cause physical changes, and will never emit electrons. In this way, the emission area of ​​the cathode becomes smaller and smaller, which is a famous phenomenon of cathode poisoning. Over time, the launching power of the tube drops dramatically, in other words, it is aging.
Since the temperature of the filament affects the performance of the tube so much, accurate filament voltage supply is very important. As the power supply voltage varies from place to place, as far as the 220v region is concerned, there is a difference between 200v in Hong Kong and 230v in uk. It is common to see a difference of up to 10%. Most of the factory machines are designed for 220v users, so it seems that the filament power supply in the machine can change by as much as ± 10% in different regions. This situation is obviously not beneficial to the durability of the tube. The level of the filament voltage is the owner ’s own responsibility, and the manufacturer ignores it. The amplifier factory is only interested in sound quality. The author has seen a famous manufacturer ’s amplifier whose filament voltage is as high as 7v. In the face of this situation, the owner What if you don't want to change the tubes every year? It seems that you can only adjust the voltage yourself as a remedy.
The author proposes to connect a 500w voltage regulator to the amplifier to adjust the input voltage in order to obtain the required filament voltage. When adjusting, the filament voltage should be measured on the tube base to get the real value, and an additional one must be installed. Hour meter to record the working time of the amplifier (Figure 2). This timer starts counting every time the power is turned on, and the reading is retained when the power is turned off, and the time is added to the original reading when the power is turned on again, so that you can know the total time the amplifier works. When a new set of pipe is put on the machine, you must record its working time, and then adjust the filament voltage of each period according to the above tips. The amplifier should be used with this voltage regulator.
Although this method is somewhat inconvenient, a 500w voltage regulator and timer are very cheap. Compared with some classic power tubes that may not be available in the future, these inconvenient expenses are negligible.
The soft start method of the amplifier's tube filament has a very low impedance when cooled (room temperature) and a high impedance when it is hot. This characteristic makes the current flowing through the filament very large when the filament is turned on for a few seconds. After returning to normal, it is common for some tubes to suddenly turn on when the filament is turned on, and then slowly dim. For a long time, of course, it is not good for the durability of the filament. Generally, the filament is burned out and this situation is related to it. Fortunately, it is not common.
In response to this problem, someone proposed a soft-start method for the amplifier. The principle is to reduce the filament voltage by 20% to 25% at startup, and then return to normal after a few seconds, so that the large current pulse at startup can be avoided and the tube is protected. .
The simplest soft start method is to use a delay relay (delay on TImer) or circuit, with a large wattage resistor, as shown in Figure 3 to connect. The delay time is only 3 to 5 seconds, definitely not too long, the resistance is suitable to reduce 220v to about 175v. Generally, the power consumption of an 80w amplifier is about 1.5a, and the power of the resistor must be 80w to be fully used. The resistance is about 30Ω. There is a resistor with aluminum heat dissipation shell, the volume is only 2 inches long and half an inch in diameter, very small, but it needs to be installed on the radiator to work. It is suitable for this purpose. The soft start method is not the same as the segmented filament power supply method above. Conflict, the two can be used together.
Improve the ventilation of the power tube. The heat generated by the power tube is large, and the temperature during operation is very high. If you want to provide long-term and reliable service, the temperature of the tube should not exceed 200 ℃. Otherwise the structure of the tube will be damaged. Generally, the amplifier uses natural cooling. At this time, the distance between the two power tubes cannot be too close. For example, larger power tubes such as kt88. When two tubes work together, the distance between the two center points of the tube base must be at least 4 inches. This is listed in the manual of the gec tube, but many famous machines that use kt88 or 6550a as the output, the distance between the tube seats is less than 3 inches, and there is no cooling fan in the machine. Some people think that there is no problem because they are different from the law, because this is the work of the master designer. Do n’t you believe it? The factory machine believes this situation is based on several reasons: First, the high temperature of the tube makes the launch force strong and the sound strong. 2. Due to the limitation of the appearance and volume of the amplifier, it is not possible to meet the requirements of the separation distance of the tube factory. Third, the durability of the pipe is not the main concern of the amplifier manufacturers, the most important thing is the sound quality.
In the past when various tube factories were still in mass production, the price of power tubes was very cheap, and there was no shortage of stocks. The longer life of the tubes is not a big problem. Now the vacuum tubes are gradually getting rich and cannot be bought. As a user, it is necessary to do some work to ensure that the tubes are durable. For the amplifiers with insufficient heat dissipation of the power tubes, it seems that they can only install an ultra-quiet small fan for the instrument next to them. . Of course, it can't be drilled and installed on the casing, so as not to damage the value of the whole machine. It is best to move it and set it aside so that the precious pipe can work at its acceptable temperature.
Conclusion The above three tricks are all practical ways to extend the life of the tube, and will not have any impact on the sound of the amplifier, even if only one of them is used. The benefits are immediate, as the so-called investment is small and the results are great. Among them, the segmented filament power supply treatment method is particularly suitable for direct heating power tubes designed in the 30s such as 300b and 2a3, and the effect is very significant. For side-heated pipes such as kt88, it is only beneficial rather than extending the working life by three times.
All three methods are using external independent devices, no need to change the machine, even if you change the machine, you can continue to use it on the new machine. The above-mentioned improvement principles are all derived from the technical data of eimac, gec and other tube factories. Although the implementation method is the author ’s own assumption, it may be lost in roughness, but the general direction is not wrong. It is worthwhile to the majority of enthusiasts. Referral.
= 25°C unless otherwise specified Symbol Pd VF RqJA Tj, TSTG Value to +175 Unit mW V K/W °C
Characteristic Forward Voltage = 200mA Thermal Resistance, Junction to Ambient Air (Note 2) Operating and Storage Temperature Range Notes:
1. Tested with Pulses, 20ms. 2. Valid provided that Electrodes are kept at Ambient Temperature.
1. Tested with pulses = 20 ms. 2. Valid provided that electrodes are kept at ambient temperature.
VZ, ZENER VOLTAGE (V) Fig. 1, Zener Current vs Zener Voltage
25 20 VZ, ZENER VOLTAGE (V) Fig. 8, Zener Current vs Zener Voltage
TA, AMBIENT TEMPERATURE (°C) Fig. 3, Power Dissipation vs Ambient Temperature
15 20 VZ, ZENER VOLTAGE (V) Fig. 4, Differential Zener Impedance
VZ, ZENER VOLTAGE (V) Fig. 5, Junction Capacitance vs Zener Voltage
Three ways to extend the life of the electron tube
The power tubes of famous factories such as we 300b, gec kt88, rca 2a3 and tung? Sol 6550 are very expensive, and except for we 300b, the other ones have been discontinued for more than 20 years, and these are becoming rare. It is really necessary to extend its life. The working period of a tube is directly related to its working environment, such as circuit design, voltage supply, ventilation and heat dissipation. The 100,000-hour working life time proposed by the factory refers to the use of the same tube in normal and good conditions. A poorly designed circuit can quickly age. The durability of the power tube used by the single-ended machine is much worse than that of the class A and B push-pull machines. The following are some of the methods collected by the author about extending the life of the tube, most of which are the data provided by the manufacturer. The electron tube machine is also a good reference.