Sound visualization on vintage lamps

Hamsters welcome you friends.

Today's post will be about sound visualization. For these purposes, rather interesting radio tubes will be used, which in their design represent miniature cathode ray tubes with a deflecting system, similar to those found in picture tubes of TVs. During the film, we learn how to run such artifacts, what features you need to consider when setting up, consider the main criteria when choosing absolutely any radio tubes and not only indicator ones. At the end, we place the vacuum tube in an elegant case that will delight you every time you listen to your favorite music.



At one time, signal level indicator tubes made a huge revolution, turning household radio receivers into something living and previously unknown to an ordinary resident of those times. In the world of the absence of LEDs and other things familiar to us, flashing lamps began to exist around 1935, and during the development they were divided into three generations. In the course, we will connect each of these samples, but for now let us dwell on the second-generation 6E1P instance .



Execution in such a case was called finger-type. Direct destination: tuning radios with amplitude modulation and indication of the recording level in tape recorders. The passport operating time is 500 hours, after which the emission is probably lost or the phosphor burns out. The filament voltage requires 6.3 volts at a current of 300 mA.



To check the radio tube, you need a socket to which it is convenient to solder the wires. You will see her further. After a little work with sandpaper, we check to see if the passport data matches the actual readings of current consumption. Maybe there was something wrong.



After connecting a filament voltage of 6.3 volts, the current from 600 milliamps began to fall, and stabilized at 320 mA as it warmed up, which is what we need. Part of the work can be considered completed, since at this stage, millions of electronic engineers manage to burn the glow, giving anything to the input. Remember! Have a passport.



Next, you need to find a constant voltage of 250 volts to power the crater anode.Usually TA24 type anode transformers are used for such purposes, but it is too large for our design. I propose another scheme, a conventional diode bridge directly from the 220 V network. At its output, approximately 210 volts are obtained, taking into account the voltage drop across the diodes and ripples of 100 Hz. We do not set a smoothing capacitor, since the voltage in this case will increase to 300 volts. Of course, such a decision is not right in the root and requires galvanic isolation from the network, but I don’t care “I am an artist, I see that”.



Such a simple connection will start the indicator lamp and allow it to be checked for operability.If you touch the first leg, it is the entrance, then the device responds well, opening the petals like a snake at the sight of danger. For proper lamp control, a negative voltage must be applied to its input. It can be formed using a detector stage consisting of two diodes.



This is the simplest control circuit; it connects to the output of a low-frequency amplifier. The minus of this scheme is that blinking here will greatly depend on the volume, you will need to turn the resistor knob each time to select the desired response threshold.



A more advanced version of the circuit consists of three cascades.The first is an emitter follower, consisting of a transistor T1, it has a large input impedance to reduce distortion of the input signal. The second is a transistor, this is an amplifier and a voltage limiter. The third - forms feedback, which helps to expand the working range of the lamp. This cascade can be disabled. Such a circuit is very sensitive, and can work at a low input signal level.



You can assemble it on the circuit board, the size comes out quite compact. Here we see 4 wires. Two of them are power, the rest are signal input and output. In order to avoid interference when listening, you must use a shielded wire, since here all the electrical interference is induced.



Now is the time to put this heap of iron in the case.Its size is small, since only the control board will fit inside. An incandescent transformer is installed on top to give surroundings. The cathode ray tube will emphasize the beauty of the transformer, or the transformer will emphasize the tube, but anyway! We drill mounting holes and carry out preparatory work on the body. The socket for the socket is milled using a bur machine. It is desirable that the part is inserted tightly, since the fasteners on the panel are not provided for by the design.



18 volt step-down transformer to power the control board. It is small in size and fits perfectly inside the case. We solder the diode bridge and the smoothing capacitor to the output, since the amplifier circuit requires a constant voltage.

We hide all connecting wires inside the case, nothing should stick out from the outside.
Ideally, all contacts coming out of the transformer should be isolated from the outside world using heat shrinkage. On the reverse side, we place the power switch. Nowhere without him. We fix the entire filling with the help of Chinese snotle, pour more so that nothing falls off during operation. Solder the remaining parts to the transformer. Here you can see two diode bridges, at the output of one 210 volts, at the output of the second 18. We catch the probe and see how things are with the negative voltage at the output of the amplifier.



Now the voltage switch on the oscilloscope is set to 2 volts cell, but to understand something when touching the wire with your fingers is not easy, the signal is jelly, it jumps back and forth. It becomes more clear with the level of the output voltage, if you connect the morse code from the phone. The entire scale on the screen takes 6 cells, 6 by 2 volts, the cell is - 12 volts. This is the control voltage output at the input of the indicator lamp 6E1P. If, for example, you play music, then the signal will look like this ...



We measure the current of the anode, the multimeter shows 2 mA. We look in the manual, and we see the same figure of 2 mA. The crater anode current is 4 milliamps. The anode of the crater is that piece of iron inside the lamp that is coated with a phosphor.



How to choose the 6E1P indicator tube ?First, look at the markings. Her year of birth is important to us. Here, for example, two samples. One of the 68th, the second of the 72nd year. You ask yes ?! So what? Nothing, except that the craters of these samples are covered with different phosphors. The peculiarity lies in the fact that the older sample does not glow in the ultraviolet spectrum. Consequently, the further operation of the lamps will be very different from each other.



Now let's see the other types of electronic light indicators. Earlier we examined sample 6E1Psecond generation. The indicator 65 with an end window is referred to the first generation. It began to be produced around 1935 by Philips and was marked EM11. Immediately, the union borrowed the idea and created its own analogue. The rapt people called the indicator “magic” or “cat's eye”. It was installed on radios SVD-9, TM-8, 9n-4, Marshal.



For a long time, the 6E5C lamp in our country remained the only one.The desire to diversify the image on the screen of such an indicator led to the development of new switching schemes. In particular, the introduction of an additional resistor into the crater circuit, which made it possible for luminous petals to overlap with a large input signal, increasing the brightness in the overlap zone. This effect in the early years of the development of amateur radio even found its response in the ether jargon: when the operator wanted to emphasize that the correspondent’s radio station is heard very loudly, it was customary to say “I accept you with an overwhelming”.



Further development of this direction led to the appearance of electronic-light indicators with a lateral screen arrangement. They were developed and released an incredibly large number. We have already examined the 6E1P lamp . The indicator is flashing now6E3P . It belongs to the third generation. The luminous pattern is two columns growing towards each other with increasing negative potential at the entrance.



The inclusion scheme for all three varieties of indicators is similar, the only difference is in the numbering of the legs. Thus, they can be easily checked for performance.



Since these lamps are a cathode ray tube with a deflecting system inside, the electron flux can be influenced by an external magnetic field.If you bring for example a permanent magnet, then you can shift the line on the anode of the crater. If you bring the magnet too close, the piece of iron inside will be magnetized and the line in the neutral position will begin to shine somewhere to the side. Work in this case does not look the best way. The same thing happened with TV picture tubes. This situation can be corrected using demagnetization.



By the way, the phosphor in the 6E5C lamp did not shine in the ultraviolet, despite the fact that it is the 62nd year of manufacture. The phosphor is the bottom. With good ambient lighting, you are unlikely to see anything.



The 6E1P indicator is the most successful in my opinion, that's why we will stop on it.Let's see how the signal is visualized in time with the musical accompaniment. Write in the comments if you are familiar with the Morse code, this was the first communication language that spread on the radio. Pretty curious thing, but unfortunately useless nowadays.



Now the morse code has been completely replaced by a matrix, this font at one time turned out to pass the physics exam, in which I was zero, our teacher did not even understand anything, a brilliant invention.



I myself had a chance to be born in a century when the only available electronic game for the people was "wait a moment" on the electronics platform. Sometimes it is amazing what interesting technologies were used long before my existence. I think we are lucky to live in the modern world of the active development of electronics.

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Full project video on YouTube
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