A simple color-musical prefix on thyristors. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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A simple color-musical prefix on thyristors. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Color and music settings

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Figure 1 shows a schematic diagram of a simple color-music prefix on D1-DZ trinistors. It contains three color and one background channel. The set-top box is powered from a 220 V AC mains using a rectifier mounted on D4-D7 diodes in a bridge circuit. The negative wire of the rectifier is connected to the cathodes of all trinistors, and the positive wire is connected to the anodes of the trinistors through incandescent lamps L1, L2, L3. The total power of the lamps included in each channel must not exceed 300 watts. The backlight lamp L4 is connected in parallel to the trinistor D2.

A simple color-musical prefix on thyristors. Schematic diagram of a simple color-music prefix on trinistors

From the output of the ULF receiver (radiola, electrophone) - the voice coil of the dynamic head - the low-frequency signal is fed to the Gn1 connector and the variable resistor R1. From the engine of this resistor, the low-frequency voltage is supplied to the winding I of the transformer Tr1. The secondary winding II of this transformer is connected to the input of the filters of all three channels. Variable resistor R1 serves to correct the signal level at the input of the filters. The need for this resistor is due to the fact that with a large signal, the L1-L3 lamps turn on and off at the same time, in time with the volume change. In this case, changing the tone does not affect the operation of the lamps. This is where the imperfection of the separation filters comes into play. This drawback can be partially overcome with the help of the resistor R1, which allows for more precise switching on and off of the lamps of individual channels.

The step-up transformer Tr1 ensures the reliability of unlocking the SCRs D1-D3. Usually, for this, the input voltage on the secondary winding of the transformer, i.e., at the input of the filters, should be about 2-3 V. At the same time, the voltage on the voice coil of the receiver may be lower than this value. In addition, the transformer decouples the AC network from the receiver with which the CMP works, which is necessary to comply with safety regulations.

The C1R3 filter passes high frequencies while attenuating low and mids. High frequency channel lamp (L1) is colored blue. The R4C2C3 filter passes the mid frequencies, attenuating the lower and higher ones. Finally, the R4R6C4 filter passes the low frequencies while attenuating the highs and mids. In the channels of medium and low frequencies, the lamps L2, L3 are colored green and red, respectively.

The attachment works as follows. In the absence of a signal, all trinistors are closed and the lighting lamps L1, L3 in the high and low frequency channels do not light up. In the medium frequency channel, the lamps L2, L4 will glow at full heat (all the voltage from the rectifier output is divided equally between the green and yellow lamps). When a low-frequency signal appears at the filter output of this channel and its value is sufficient to open the D2 trinistor, the L4 background lamp will go out (it will be shorted by the open trinistor), and the L2 lamp will light up with full heat. Accordingly, the lamps L1 and L3 will glow only when the voltage at the output of the filters of the high and low frequency channels becomes sufficient to open the SCRs D1 and D3.

It should be recalled that the trinistor opens only with a positive half-wave of a low-frequency signal and closes every half-cycle of the AC mains voltage.

In the manufacture of the set-top box, you can use fixed resistors MLT-1 or MLT-0,5 in it, a variable resistor R1-wire, of any type; permanent capacitors MBM or others for an operating voltage of at least 400 V. The Tr1 transformer is made on a Sh 12X12 core. Primary winding I contains 210 turns of PEL-1 0,2 wire, winding II-3200 turns of PEL-1 0,09.

Trinistor KU201K can be replaced by 2U201K, 2U201L, KU201L, 2U201Zh and the like. Diodes (D4-D7) D243A, D245A, D246A can work in the rectifier, which, without additional heat sinks, are able to provide a current in the load of about 5 A.

The design of the attachment can be very diverse. However, the general requirements are reduced to compliance with safety regulations. Reliable isolation of the circuit board with diodes and trinistors must be ensured. The latter should be installed under the nut on an additional heat sink, which can be used strips of brass or duralumin 3-4 mm thick and 50 X 150 mm in size. Mounting of heat sinks with trinistors and other parts is carried out on a board made of getinax or textolite 3-4 mm thick. If the set-top box is assembled from obviously tested and serviceable parts and correctly installed, it immediately starts working.

By setting the handle of the variable resistor R1 to the lowest position according to the diagram, a mains voltage of 220 V is connected and a musical program is fed to the input of the set-top box from the output of the receiver, electrophone or tape recorder. Then, gradually increasing the voltage at the input of low-pass filters with resistor R1, they achieve stable operation of the set-top box and the best combination of colors on the screen. Screens can be of any design.

Some radio amateurs make screens in the form of decorative table lamps or spotlights installed at different ends of the room and the light from them is directed to the middle of the ceiling.

Author: Bastanov V.G.; Publication: cxem.net

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