Toyota 

Constructions of simple complexity. Audio receiver Name in receiver

The receiver is designed to receive audio from MB and UHF television channels. Despite its wide capabilities, it is very simple, both in manufacturing and in the selection of parts. The circuit is based on a VHF-FM radio receiving path on a KS1066XA1 microcircuit (from a radio set purchased in a store) and two selectors SKM-24 and SKD-24 from an old domestic TV. Plus, a pulsed voltage source of +33V for adjusting ranges. Three ranges (MV1, MV2 and UHF) are switched by a mechanical switch, and the tuning is smooth, using a multi-turn variable resistor (tuning resistor from the receiver from the radio set).

Channel selectors SKM-24 and SKD-24 are included according to the TV circuit diagram. Switch S1 selects the range. There is no AGC system, it is replaced by a divider R1/R2 giving 8V at pin 6 of SKM-24 and 4 of SKD-24

The receiver is powered by a voltage of 12V. To obtain the voltage necessary to set the selectors to channels, a pulse source is used on the D1 chip. The multivibrator on D1 produces pulses with a frequency of about 70 kHz. These pulses arrive at the transistor switch at VT1, in the collector of which inductance L1 is turned on. About 50V is “pumped” across the inductance, then this voltage is rectified by diode VD2 and smoothed by filter C10-R6-C8.

Zener diode VD1 stabilizes the voltage at 33V. Such a source allows a load current of up to 5 mA with a stable output voltage. This is more than enough for normal selector settings.
The K155LA3 microcircuit is powered from a 12V source through resistor R8, which dampens excess voltage.
The setting element is a multi-turn variable resistor R5.

The IF voltage from the output of the SKM-24 / SKD-24 selector system is supplied through capacitor C4 to the input of the VHF-FM receiving path made on the At chip. This circuit is based on the receiving path of a VHF-FM receiver from a radio set purchased in a store. The difference between the circuit and the radio dial circuit is that the warcap and tuning resistor are eliminated, and instead of a volumetric local oscillator coil, an IF circuit coil from the 3-USTST TV (from the SMRK-2 submodule) is installed.

This L2 coil in the TV operates at a frequency of 38 MHz, here the circuit frequency on it is reduced to 31.5 MHz by replacing the 82 pF circuit capacitor with a 91 pF capacitor. To install the new coil, four additional holes were drilled in the board from the radio set for the terminals of the coil frame. Installation and fastening - by winding and soldering onto these contacts from the print side.

Additionally, a parametric stabilizer on the VD3 zener diode is introduced into the VHF-FM circuit circuit, which reduces the supply voltage A1 to 5 V. Coil L1 is wound on a ferrite ring with a diameter of 12-15 mm, it contains 250 turns of PEV-0.12 wire

The receiver is operational after the first turn on. The setup consists of adjusting the L2 coil for the best reception quality. During this, you need to remember that adjusting the L2-C17 circuit changes the entire receiver tuning, and therefore, when adjusting L2, you need to hold the tuning to the TV channel by slightly turning the R5 knob.

The receiver is designed to receive audio from television programs. It is made mainly on an accessible element base (channel selectors SKM-24 and SKD-24, fixed settings unit USU-1-15, and VHF-FM receiving path on the TA2003R microcircuit).

The device is based on an all-wave VHF-FM receiver. The difference lies in the use of more accessible and cheaper units from color TVs of the 2-USCT-4 USCT line, high-frequency units SKM-24 and SKD-24 and unit USU-1-15. Functionally, the receiver circuit is divided into five complete units - ready-made blocks SKM-24, SKD-24, USU-1-15 and a home-made IF unit on the TA2003R chip.

The general circuit diagram is shown in Figure 1. No explanation is required. SKM-24, SKD-24 and USU-1-15 are connected according to a scheme similar to the standard one. Transformer power supply on T1. To obtain the tuning voltage, the entire secondary winding T1 is used. A voltage of 12 V is obtained using the integrated stabilizer A1, and a voltage of 4.5 V to power the IF path is obtained by a parametric stabilizer on VD2.

The schematic diagram of the IF path is shown in Figure 2. The intermediate frequency signal of 31.5 MHz from the output of SKM-24 is supplied through C2 to the input of the RF amplifier included in A1. There is no input circuit; the output circuit of SKM-24 acts as such. At the output of the RF amplifier (pin 15), circuit L1 C3 is turned on, tuned to 31.5 MHz. From the output of the RF frequency control unit, the signal is supplied to the frequency converter through the internal circuits of the microcircuit. The local oscillator is also part of A1; its circuit, tuned to 25 MHz, is connected to pin 13 of A1.

The intermediate frequency signal of 6.5 MHz is isolated by a positive piezoceramic filter Q1 at 6.5 MHz from the IF path (SMRK) of a TV type 3-4USCT.
Next comes the frequency detector, it operates the C6 L3 circuit, tuned to an intermediate frequency of 6.5 MHz. Resistor R1 slightly reduces the quality factor of the circuit to reduce distortion during detection.

The IF path is assembled on a printed circuit board made of single-sided foil fiberglass. To wind the coils of the IF path, frames with ferrite boat builders and screens from SMRK-1-4, SMRK-1-6, SMRK-1-2 TV modules of the 3-USCT series are used. Coils L1 and L2 each contain 5 turns, coil L3 contains 16 turns. All are wound with PEV 0.28 wire. Piezoceramic filter FP1P8-62-02 (at a frequency of 6.5 MHz, bandpass, from the PFC path of the 3-4-USCT TV). The rectifier bridge KTs407 can be replaced with KTs405, KTs402 or assembled with diodes.

The transformer uses a ready-made low-power transformer made in China, which has two secondary windings of 12 V each (one winding of 24 V with a tap in the middle). It can be replaced with any other power transformer with a power of up to 10-15 W, producing the same secondary voltages. Or rewind the secondary winding of another transformer of the same power.

Only the IF path needs tuning. If you have an RF generator, you need to tune the circuit to the frequencies indicated on the diagram. If there is no generator, you can use the radio path of a working TV type 3-USTST as one. You need to remove the SKM-24 from the TV, and apply a signal (via a coaxial cable) from the SKM-24 output of this receiver to the input of the IF path of the TV.

Connect an antenna to the receiver and use the USU-1-15 setting to tune in to the signal of any television center. Next, turn off the TV, disconnect the output of the SKM-24 receiver from it, and connect it to the input of the configurable IF path. Now all that remains is to carefully sequentially adjust the circuits L2 C4, L3 C7 and L1 SZ to achieve high-quality sound reception.

It should be noted that this type of setup requires a lot of time and is not always successful, therefore, it is still advisable to work with a generator.

This radio may be useful for people who, due to their work, have to spend a lot of time driving. As a result of long trips, you have to miss interesting TV shows. Of course, you can take with you a small-sized TV powered by a battery, but you still have to listen to it rather than watch it, and the quality of the radio path and sound of such TVs is low, not to mention fragile.

It is much easier to take with you only the radio path of a TV, of a fairly high class, and use the amplifier of a car tape recorder as an ultrasonic sounder. It is even more convenient if such a device has a smooth scale, graduated in the numbers of frequency channels, this will make it easier to change direction when moving from the coverage area of ​​one television center to the area of ​​another.

The schematic diagram of such a radio receiver is shown in the figure. In practice, this is a simplified radio path of a 3USCT type TV. It consists of a meter range channel selector and a radio channel submodule, which contains a signal processing path for the intermediate frequency of image and sound, as well as a sound pre-amplifier. The sound path of USST TVs has incomparably better sound quality compared to small-sized TVs.

Using ready-made modules from a TV allows you to make a set-top box without spending a lot of time searching for individual parts and manufacturing and installing printed circuit boards.

The signal from the antenna is fed to the input of the channel selector SKM 24. The selector has two frequency converters with separate power circuits. The first converter is turned on by applying a 12V voltage to the seventh pin of the selector. In this case, frequency channels from 1 to 5 are received (frequency range 55.25 - 99.75 MHz).

When the supply voltage is switched from the seventh to the third contact of the selector, the second converter is turned on and the sound of channels from 6 to 12 is received (frequencies 181.75 - 229.75 MHz). The voltage of the intermediate frequency of sound and image is removed from output 1 of the selector and is supplied to the 20th output of the SMRK-2 radio channel submodule, in which these intermediate frequencies are amplified and converted, the result of which is the selection of the second intermediate sound frequency of 6.5 MHz.

Which is then amplified and detected, and the low-frequency signal is removed from pin 3 of the SMRK-2 and through a standard five-pin (round, such connectors are used to connect a set-top box tape recorder to an amplifier, and in other cases) the low-frequency connector is supplied to the ultrasonic input of a car tape recorder or radio. Through this same connector, supply voltage is supplied to the circuit, and by shorting pin 3 of this connector to the common wire, you can block the set-top box.

Switching ranges (1-5/6-12) is done by microtoggle switch P2 type MT-1 or MT-3, the same toggle switch turns off the APCG system. In addition to the APCG voltage, SMRK-2 generates the AGC voltage for the selector. Trimmer resistor R3 sets the desired level of the HF signal, which is fed to the tape recorder amplifier.

The tuning voltage for the selector varicaps is supplied through its pin 4. To tune to all channels, you need to adjust this voltage from zero to 30 V. To generate this voltage, a blocking generator is used on transistor T1. The alternating voltage from the secondary winding of the transformer is rectified by a rectifier using diode P2 and capacitor C6. Then this voltage is lowered to the level of 31V by the zener diode D1 and through the setting resistor R5 and R4 it is supplied to the fourth terminal of the selector. The AFC voltage from the SMRK also comes here.

The set-top box is housed in a metal case with dimensions of 150x50x120 mm. A selector is screwed onto the bottom of the housing using a clamp; on the opposite side, a submodule is screwed onto the cover using three M3 screws. Thus they are located parallel one above the other.

The voltage converter on transistor T1 is mounted in bulk and placed in a housing from an electromagnetic relay of type RES-6 and filled with epoxy resin. The relay body acts as a screen. Transformer Tr1 is wound on a ferrite ring K16x10x4. The primary winding contains 4+10 turns of PEV-0.31 wire, the secondary winding contains 56 turns of PEV-0.12. Capacitor C6 should have a voltage of at least 50V.

Instead of SMRK-2, you can use SMRK-1-5 or -1-6. There is a linear adjustment scale at the end of the housing. The tuning knob is connected to the resistor R5 slider using a rope vernier that creates deceleration.

The schematic diagram of channel selectors SK-D-24 and SK-M-24 is shown in the figures below.

Channel selector SK-D-24

UHF channel selector SK-D-24 032.222.016 is designed for selection, amplification and conversion of UHF television radio signals into intermediate frequencies.
Main technical data and characteristics:

  • Frequency range. MHz.... 470 - 790;
  • Noise figure, dB. no more.... 11.5;
  • Gain, dB. no less than.... 7;
  • Rated supply voltage, .... V 12;
  • Voltage limits of the varicap control circuit, .... V 0.6 - 25.2 V;
  • Nominal AGC voltage. AT 8;
  • Current consumption, mA, no more.... 15;
  • Weight, kg, no more.... 0.12;
  • Overall dimensions, mm, no more.... 93 * 61 * 25;
  • Content of precious materials: gold - 0.0234 g; silver - 0.0646 g.

Rice. 1. Schematic diagram of the SK-D-24 channel selector.

Channel selector SK-M-24

The meter range channel selector SK-M-24 0E2.222.015 is designed for selection, amplification and conversion of meter range television radio signals into intermediate frequency.
Main technical data and characteristics:

  • Frequency range, MHz 4.... 8.5 - 230;
  • Noise factor, dB, no more than.... 9.5;
  • Gain, dB, not less.... 15.5;
  • Rated supply voltage, V.... 12;
  • Voltage limits of the varicap control circuit, V.... 0.6 - 25.2;
  • Rated voltage of AGC, V.... 8;
  • AGC control depth, dB, not less.... 24;
  • Current consumption. mA. no more than.... 25;
  • Cash register, kg, no more.... 0.160;
  • Overall dimensions, mm, no more.... 97 * 85.5 * 25;
  • Content of precious materials: gold - 0.0361 g, silver - 0.232 g.

Rice. 2. Schematic diagram of the SK-M-24 channel selector.

Connection diagram for SK-D-24 and SK-M-24 modules

Rice. 3. Connection diagram for channel selectors SK-D-24 and SK-M-24.

Repair and adjustment of high-frequency units of black-and-white TVs

The channel selector (SC) is designed for selection, amplification and conversion of high-frequency signals into intermediate frequency signals. The SC includes a high-frequency amplifier, a mixer and a local oscillator.

According to their design features, channel selectors can be divided into tube television channel switches (PTK); transistor selectors with mechanical channel switching; transistor selectors with electronic adjustment.

The qualitative parameters of the SC are characterized by: voltage gain - the ratio of the voltage at the output load of the channel selector to its input voltage, expressed in decibels; Frequency response determined by the parameters of input circuits and UHF bandpass filters; instability of the local oscillator frequency during warm-up, caused by the deviation of the local oscillator frequency during a certain warm-up time of the SC.

Let's consider the circuit design of the SC. All tube television channel switches (PTS) contain a 12-section drum switch, each sector of which corresponds to 12 television channels.

An SK-D unit can be connected to PTK-11D, which provides reception of TV broadcasts in the decimeter wavelength range (band III), while the PTK mixer is used as an additional intermediate frequency amplification stage. The design of the meter channel selector (SCM) is similar to the design of tube PTCs, but the SCM, used in portable TV modules to reduce size, has a dial switch for television channels (SCM-20). In Fig. 7.3, and shows a schematic diagram of SKM-15, designed for all classes of black-and-white and color televisions, made using transistors.

The antenna is connected to the input circuit L7, L8, C4^C5 through a filter LI, Cl, L2, C2, L3, SZ, L4, which serves to provide the necessary noise immunity via the forward channel. The high-frequency amplifier is assembled on transistor VT1 according to a circuit with a common base. UHF uses specially designed high-frequency transistors GT328, which have a pronounced dependence of the gain on the emitter current. The AGC voltage is supplied to the base circuit of transistor VT1. The local oscillator is made on transistor VT3 according to a capacitive three-point circuit. The transistor mode is set by resistors R8, Rll, R19, R10 and zener diode VD1. The APCG voltage is supplied to the varicap VD2, partially connected to circuit L11 through capacitor 016. Transistor VT3 is connected according to a common base circuit. The SKM mixer is made on transistor VT2 according to a common emitter circuit. The local oscillator and UHF signal is supplied to the base of the transistor; an L6C22 intermediate frequency filter is included in its collector circuit. When receiving in the DCV range, the signal from the ACS through the bandpass filter C27, L5, C26, C25 is supplied to the base of the transistor VT2. The mixer in this case serves as an additional cascade of the UPCH, and the power to the UHF and SCM local oscillator is turned off.

Television channel selectors with electronic adjustment are similar to those described. They use smooth adjustment of circuits with varicaps and switching ranges with diodes. Note that a twofold construction of the SCM is possible. In the first case, amplification and conversion of signals is carried out by a common path in frequency ranges I, II and III (for example, SKM-18, SKM-30, SKV-1), in the second, separate paths are used for ranges I, II and III, the mixer remains common (for example, SKM-23, SKM-24).


Let's consider the construction of SCM 24-2 (Fig. 7.3, b). Signals in bands I and II are amplified by UHF, collected on transistor VT2 according to a common base circuit, signals in band III are amplified by UHF, collected on transistor VT1. Heterodynes of ranges I, II and III are made, respectively, on transistors VT4 and VT5 according to the circuit of three-point capacitors with a common base. For both amplification paths on transistor VT3, the mixer is common. The ranges are turned on by applying voltage to the emitters of the transistors of the corresponding path. The circuits of idle SCM cascades and the mixer inputs are turned off by diodes VD3, VD4, VD9, VD11. UHF of both bands are controlled by AGC voltage. To reduce interference along the forward channel at the intermediate frequency, a filter LI, C1, L3, C2, L4, SZ, L5, L6, C4 is included at the SCM input. The SKD is turned on by the VD10 diode, while the power from the UHF and local oscillators is turned off, and the SKM mixer serves as the first stage of the UPCH.

The SKM SKV-1 and SKM-30 use a common AMP for all ranges, controlled by the AGC voltage. The mixer is designed similarly to the SKM-24 (as is the local oscillator). Switching ranges is carried out by switching selective circuits with diodes. SKM-30 differs from the previous ones in the construction of UHF, which is made according to a cascade circuit OE - OB on two transistors.

UHF channel selectors are designed to amplify and convert TV broadcast signals in the UHF range into intermediate frequency signals and work in conjunction with SCM. In the SKD, the local oscillator is combined with a mixer. The tuning element can be variable capacitors or varicaps. Examples of SKD with mechanical adjustment are SKD-1, SKD-20. Electronic tuning is used in SKV-1, SKD-23, SKD-24, SKD-30. At frequencies in the decimeter range, resonant systems cannot be constructed on conventional circuits, therefore half-wave or quarter-wave long lines are used in ACS units for selective circuits. When using segments of half-wave lines, a tuning element can be connected to one end of the line, and an active element (transistor) can be connected to the second. One end of the quarter-wave segment of a long line is grounded, and the other is loaded with a tuning element and a transistor. Note that quarter-wave lines make it possible to reduce the dimensions of the ACS unit. SKD with half-wave asymmetrical long lines includes SKD-24 (Fig. 7.3, c).


The high-frequency amplifier is made on transistor VT1 according to a circuit with a common base. The AGC voltage is supplied to the base circuit through resistor R3. At the UHF input, a filter L1, C1, L2 is included, which provides filtering of signals from television stations in the meter wavelength range. The UHF output is loaded onto a bandpass filter L6, L10, connected to ground by capacitors CIO, C12. On the other hand, the lines are adjusted by varicaps. The mixer is made combined with a local oscillator based on transistor VT2 with similar adjustment elements. The pairing of the UHF and local oscillator circuits is ensured by selecting the capacitance-voltage characteristics of the varicaps VD2, VD3, VD4. Structurally, all types of SKD are made in a metal case, consisting of five sections, closed with common metal covers.

All wave selectors (SKV-1, SKV-2) combine SKM and SKD in one housing. Their circuit design is similar to that of the described SCM and SKD.

The operation of electronically tuned channel selectors is controlled by electronic program selection and switching devices. Program selectors (PSS) are divided into three types: touch, pseudo-touch and push-button.

Defects in PTC, SCM and SKD manifest themselves in basically the same way. If the unit malfunctions, the image and sound disappear. Sometimes there is no sound when there is a picture and vice versa. The image may be very noisy, there may be no reception on any one channel or band (for SCM with electronic tuning).


A typical malfunction that often occurs in high-frequency units PTK, SKM-15, SKM-20 is that the image and sound appear when the switch knob is pressed or turned. This defect is associated with deterioration of contact in the channel switch and can be eliminated by removing the block, disassembling it, washing (with alcohol, acetone) the drum contacts and the spring petals of the contact strip, followed by assembling the block. Washing the contacts does not always lead to the desired result; in this case, it is recommended to bend the petals of the contact strip and clean the contact groups with a pencil eraser. The troubleshooting algorithm for PTC, SCM and SKD (Fig. 7.4, a) is based on the method of sequential intermediate measurements.

The TV channel selector is adjusted after replacing faulty parts, which usually does not cause a significant detuning of the unit’s characteristics. Changes in the installation design associated with repairs may affect the unit parameters. Regulation of PTC, SCM and SKD is carried out using an frequency response meter, a signal generator and the PNP-3 device (PTK adjustment device). A block diagram of switching on devices for setting TV channel selectors and measuring parameters is shown in Fig. 7.4, b.

The frequency response image is obtained on the oscilloscope screen or IFC screen after detecting the intermediate frequency signal. The IFC includes a detector section, and the PNP-3 device includes a load equivalent and an intermediate frequency signal detector. An equivalent load is required if channel selectors are configured without specialized devices. In general, the equivalent load for tube selectors is high-impedance (Fig.

7.5, a), for transistor selectors - low-resistance (Fig. 7.5, b).

When working with an IFC or sweeping frequency generator, it is necessary to match the high-frequency output of the device and the input of the TV channel selector. When setting up, it is not advisable to connect the generator and the channel selector with a cable, since the observed shape of the frequency response depends on its length and location (the traveling wave mode is not implemented in the cable). The IFC generator must be switched on through a matching device (Fig. 7.6) or an attenuator with an attenuation of 9.5 dB. In this case, the value of the input voltage (Lx = (Len /3.


Setting up and adjusting channel selectors involves a set of works to check and set the required amplitude-frequency characteristics of the block stages and its end-to-end characteristics, setting the nominal frequency of the local oscillator and the selector gain. The setup is carried out in the following sequence: initially, the IF circuit is set up, then the input IF signal suppression circuit is set, the nominal frequency of the local oscillator is set, the input circuits are adjusted and the frequency characteristics are corrected on each TV channel, starting from the highest.

By connecting the channel selector to a power source and assembling a circuit similar to that shown in Fig. 7.10, adjust the output circuit of the inverter until the required characteristic is obtained (Fig. 7.7, a). The signal from the output of the IFC sweep frequency generator is fed to the KT-1 control point (SKM-15, PTK-PD) through a capacitor with a capacity of 5-6 pF, the output is connected through the detector to the IFC input. Tube PTCs are characterized by a double-humped frequency response.

The local oscillator is configured as follows. By simultaneously applying the RF signal from the IFC and the carrier frequency signal of the tuned TV channel from the high-frequency generator to the input of the channel selector, set the voltage on the varicap to 5 V and adjust the local oscillator circuit with the core until the generator frequency conversion mark aligns with the 38 MHz frequency mark on the IFC screen . Having aligned the marks, check the effect of frequency adjustment by changing the voltage on the varicap. The local oscillator frequency should be offset by ± 1 MHz from the carrier. The frequency response of the RF frequency response is observed by connecting the IFC input to the KT-2 (SKM-15) control point (Fig. 7.7, b). If the characteristics do not match, adjust the input circuit or the UHF selector bandpass filter. The selector gain is determined by changing the IFC generator signal by 10 times using an attenuator, and then the resulting frequency response is measured with and without an attenuator:

Where U is the average amplitude of the end-to-end characteristic; Ua is the amplitude of the frequency response with the attenuator turned on.

Adjustment of channel selectors with electronic settings is carried out in the same sequence