For many friends, you often need to purchase some tubes. Domestic, imported tubes, new and old, brand different, how to buy a cheaply combined pipe, there are many learned.
Everyone usually has two ways to buy, one is to buy in the market, and the other is online purchase. Generally speaking, buying itself in the market is reliable, the price is also relatively inexpensive. At that time, everyone can measure it with a variety of methods. However, I used to buy tubes here usually not have measurement conditions, and the aim of the bonus is also Feng Fu. So it is often a mess to buy some tubes, so that people 's garbage becomes RMB, let their own renminbi become garbage.
Everyone has the experience of online buy management. I can use a hand online. I can't talk about it. I can't talk about it. Here I am talking about is a problem.
First of all, it is the problem of second hand and new management. It is often seen that some imported second-hand tubes are high, especially small tubes that have been used by some sounds, more than 12AX7 12AT7 12au7 6dj8 and their European models, and say that these tubes I have never used it. But I think that the second-hand pipe is always better than the new pipe. Often to see some old can't sell the old tube is very "reluctant", some beginners, spent a big price, bought these things that couldn't use it, and then use it. I feel very bad. In fact, if you are using it on the instrument, you can easily understand that the parameters of the old pipe is not as good as new products, and no matter how the brand is not. Even if the radio is used, it is also very easy to distinguish. For example, the frequency tube 6SA7, I have experimented that different new and old terms of different manufacturers are used in the same radio, sensitivity, signal-to-noise ratio is absolute and new and old, and there is no difference from the manufacturer. The second-hand 12at7 6SN7 sold by those traitors often cannot continue to be used on the device, but the simple circuit of the electronic tube megaphone is not sensitive to such a pipe, not in the stuffing.
For the brand of the tube, I have always been unpick. Recently summarized the problem of the tube used, and discovered that the different quality of the brand is also high. It is worth pointing out that the quality of the quality is a radio tube manufactured by Japan during World War II. Even the devils acknowledge that the civilian pipe has been very crude. Personally, the quality of RCA is better, measuring some RCA early pipes, UX250 2A7 6D6 71A 80 and later 50L6GT, etc., the parameters are good, and the mechanical performance is also good. However, there is a slight leak of 2A3. I think it is good to say that it should be relatively good. A few days ago, I once said that I showed an EF860 that was off. This proved a problem. This tube used to be seriously hit. It is not broken, and it may be broken. Because the deeper ring is welded on the inner electrode, the manufacturing level of VEB-RFT is definitely not even welded, and this circle can be absorbed, the pipe electrode is completely normal, and it is not easy. This color has made me. In the domestic pipe, the Shanghai 80s 6K4 problem is more, and there is nothing serious. However, the mainstay of the cottage factory in Tianjin is very popular, and advise you still don't have to try.
Listening to "Master" said that the sound use tube is a one to learn, it seems that I can't understand it. However, choose the pipe for the radio, I still dare to say two sentences. The tube in the radio allows us to use a new pipe as possible. The old pipe is easy to cause a variety of problems, often not solved. Especially if you use 6A8 frequency conversion, 6A8 must be good, so you can buy a new Soviet 6A8, some of the early 2A7, 6A7 is best, 6A2, 6SA7 is better because of the characteristics, can be loose. The new 6k4, 6k3p in the middle is very good, the second-hand foreign goods 6k7 is good, it is best not to use, the second-hand 6k4 is not used, absolutely not.
The 6G2P of the detection is better to find new products, with a new 6N9P, 6B8P, 6N2, and old 6SQ7, 6q7, 6g2 caution. This is mainly to ensure that the electrical parameters of the detection section should be guaranteed, especially the starting characteristics of the diode, the forward resistance, and the like are strict. As for power amplifying tube, use old tubes, inexpensive 6p1,6p6p or various 6F6, 6k6, 6v6, if there is no pair of 6L6, 6G6, 6Y6, etc., etc., can change cathode resistance and use appropriate output transformers. In the future, switching, selecting a small working state of the current on the manual. The rectifier tube is not particular, second-hand, as long as there is high voltage output. This part even is not good in quality, there is a problem, and it is also easier to check, and the output voltage is known. Domestic 5Z2P 5Z4P, various 80 5Y3 5W4 5Z4, etc. can be. Without 5V filaments, it is good to use 6Z4 6Z5P 6x5. The transistor is no problem. Not afraid of charge, there is a large current filament 5Z3 5U4G 5V4, etc.
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