New features of the old TV with SDU. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Телевидение

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Additional control of VHF radio, stereo amplifier and lighting

One of our contributors decided to add features to his old TV, which already had an optional remote control system installed. As a result, with the same remote control, he can control not only the TV itself, but also the built-in VHF radio receiver, and the stereo amplifier with a stereo broadcasting decoder, and the lighting in the room. How he did it, and described in the published article. If in the future the TV set is equipped with a demodulator - a NICAM signal decoder, it will be possible to receive stereo sound accompaniment of television programs, which has already been started both in Ukraine and in Russia. Radio amateurs opened up a large field of creativity in this direction.

In recent years, the modernization of third-fourth generation TVs, which still make up a very large part of the fleet of the population, has been and continues to be paid quite a lot of attention, mainly for economic reasons. After all, after installing a remote control system (SDU), an all-wave channel selector and a color block on the latest elements, you can get a completely modern device at relatively low material costs. This path is aimed at realizing the possibilities that modern models already have. However, another option is possible - the introduction of new consumer functions that modern TVs do not have (still or already is another question). Modernization in this direction will be discussed. Although the introduced functions are quite simple, the main thing is to start.

The TV set "Electron - 61TTs450D" with the previously installed SDU with the remote control RC-6 has undergone additional modernization. The lack of AV inputs and outputs in the majority of old TVs prompted the improvement, which is why one of the SDU control outputs turned out to be free. Therefore, the idea arose to use it for switching some more loads. In order to have several of them, in addition, for the purpose of control, the switching voltage of the subbands received by the TV (l-ll - VHF-1, III - VHF-3 and IV-V - UHF) was used. In addition to saving all the functions as a TV, the newly introduced blocks allow you to control the power switches of two loads, the parameters of one of them, as well as the built-in VHF radio receiver.

If load management can be attributed to the new functions of the TV, then combining it with a VHF radio receiver is not yet very forgotten old. Radio reception on VHF was implemented in televisions manufactured in the 50s with separate channels of sound and image "North", "Luch", "Zenith", etc. Later, in models with a combined channel, a second local oscillator was used for this purpose ("Record ", "Znamya", "Rubin") or a separate receiving unit for VHF FM stations ("Temp-3", "Rubin-102", "Start-3"). Then the paths of broadcasting and television diverged. However, in modern portable TVs, reception of broadcasting stations is still provided.

As for the loads, one of them is an emergency lighting with the possibility of remote or manual switching on or off. The second load is an external stereo amplifier with a stereo audio signal decoder. Through it, you can listen to the speaker system as the sound of TV programs, as well as stereo programs of VHF radio stations. There are remote volume control and mute modes. If necessary, you can enter the remote control of bass, treble and balance. Loads can be controlled regardless of the TV operating mode: ready (SB-standby mode), receiving TV programs or VHF broadcasting stations.

When the mains voltage is applied, the loads are set to the off state, and the TV is set to standby mode. In this mode, you can manually (not remotely) turn on or turn off the loads, as well as turn on the device in the television reception mode. This is provided in the event that for some reason it is impossible to control it from the remote control. There will be no VHF reception, which will indicate the need to change the batteries or repair the remote control.

With a working remote control, the transition of the device from the SB mode to the working one is provided in the usual way, as provided for in the SDU. However, the VHF radio reception mode is turned on first. It allows you to manually or remotely select pre-programmed stations and use all the functions of the CDS: automatic tuning to stations with subsequent memorization, muting the sound, using a timer, fine tuning to a station, volume control, etc. You can listen to transmissions both on the internal amplifier 34 and dynamic heads, and through an external stereo amplifier with a stereo decoder and speaker system. When the external amplifier is turned on remotely or manually, the internal amplifier turns off.

Switching to the mode of receiving television programs occurs when you press the AV button on the remote control. After pressing the TV button in this mode, all standard functions provided by the CDS are implemented. The transition to SB mode is provided as usual.

The connection diagram of the device modules is shown in fig. 1. Remote control (RC) and standby (DR) modules are included in the CDS package and used with minor modifications (more on that later).

Control and switching modules, as well as power modules located in electrical sockets, are subject to manufacture. The circuits of the XS4 connector of the control module are connected in parallel to the corresponding circuits of the remote control module SDU. Two other loops of the remote control module are connected to the control and switching modules. All connections are made with flat cables (loops).

The schematic diagram of the control module is shown in fig. 2. Channels for switching loads are made in the same way. Their functioning is as follows. UHF or VHF-3 signals for another channel and AV are input to the element DD1.1 and DD1.2. Therefore, as a result of the operation of these elements, the selection of the desired channel is provided by the UHF or VHF-3 signals, and the switching of the loads is provided by the AV signal. For manual control of loads, elements DD1.3 and DD1.4 are used, respectively. Load operation mode (on/off) is determined by the state of triggers DD3.1 and DD3.2. Their initial installation at power-up occurs through the C5R15 circuit. Through power amplifiers on transistors VT2 and VT3, control signals pass to thyristor optocouplers of power modules.

The switching channel of television or broadcasting reception is assembled on triggers DD2.1 and DD2.2. If the VHF-1 signal is present at the input D of the trigger DD2.1 and the signal AV appears at the input C, a single vibrator is started, made on the trigger DD2.1 with the reset circuit R12C2. The pulse generated by the single vibrator affects the input C of the DD2.2 trigger, which switches the reception modes. Manual switching occurs at the input S of the trigger DD2.1, and the initial installation - at the input R of the trigger DD2.2 by the C6R14 circuit. Moreover, this circuit is connected to the output of the remote control module that controls the turning on of the device, therefore, when turned off, the device switches to radio reception mode and is immediately turned off by the transistor VT1.

In SB mode, the opening voltage comes to the base of the transistor VT1 from the remote control module, so the transistor is open, the Rx circuit of the VHF receiver is closed and it does not work.

Therefore, the operating mode of the device is selected from the remote control by setting the required sub-band UHF, VHF-3 or VHF-1 (i.e., one of the programs of each sub-band), and then press the AV button and switch either the load or the TV with the receiver. The enabled subband is indicated by LEDs HL1-HL3 on the front panel of the module. In SB mode, the HL3 LED lights up "half-heartedly". Structurally, the LEDs also serve as buttons for manually switching modes.

Direct control of the device supply voltages is provided by the switching module, the schematic diagram of which is shown in fig. 3. On the transistor VT1, a key is assembled that controls the network relay located in the DR module.

The appearance of a TV signal triggers the key and connects the TV to the network, resulting in the reception of television programs. In the VHF radio reception mode, the device is powered by the transformer of the DR module. In this case, a constant voltage of about 15 V is supplied to the key, made on transistors VT2 and VT3. If there is a Fix signal to turn on the radio, the key opens and the supply voltage passes to the stabilizer DA1 and the power switch of the amplifier 34 on transistors VT4-VT6. At the same time, the VT3 transistor provides blocking of the UPCHZ of the TV. From the DA1 stabilizer, a voltage of 12 V comes to the remote control module (via the XS1 connector), the control module and the UPCHZ of the TV. The state of the amplifier power switch 34 is determined by the mode of operation of the stereo load amplifier 1. If the load is on, the switch is closed and the TV's internal 3H amplifier is de-energized.

The power supply of the remote control module must be provided both in television and radio reception modes, therefore, combine the power circuits with diodes VD3 and VD4. A similar solution is provided for the tuning circuit with a supply voltage of +31 V (diodes VD5 and VD6). However, the apparatus assumed the possibility of using the all-wave channel selector of the TV as an input device for the VHF receiver, and the latter would then be tuned to the sound IF. So it would be possible to receive not only radio broadcasts, but also the sound accompaniment of all television programs. For this purpose, a tuning voltage of +31 V is required, which is why a voltage multiplier with a stabilizer on the elements C3, C4, R12, VD7-VD11 and the R5R6VD2 AGC circuit were introduced. In the final version, the author refused this possibility, so the listed elements are shown with a dashed line (they are not installed). Those who wish can do this by installing an all-wave channel selector on the TV instead of separate meter and decimeter channels.

The tuning voltage for the radio receiver is supplied through the P1 jumper and the VD6 diode from the DA1 stabilizer and is equal, as indicated, to +12 V. It is quite enough to cover the VHF broadcasting range.

The device uses a standard DR module, modified according to the scheme in Fig. 4. The improvement consists in installing a more powerful transformer T1, a larger filter capacitor C1, a four-pin connector and connecting the circuits according to the diagram. You can use the TVK-110LM transformer from tube TVs.

Power modules are assembled according to the same scheme shown in fig. 5, and have no features. It should only be recalled that triacs TS106-10 produced until the mid-90s have the location of the conclusions on the side of the inscription UE, 2 (A), 1 (K), later - 1 (K), 2 (A), UE.

Changes in the blocks and modules of the TV are as follows.

In the submodule of the radio channel, it is necessary to install pin 9 in the X2 connector (the designations of the connectors are according to the TV diagram). The required changes in the submodule must be made according to the scheme in Fig. 6, a. This is how the power supply of the UPCHZ is provided.

A four-pin connector is placed on the connecting board (except for PS-50), soldering it to the printed conductors going to pins 10 and 11 of the X4 connector. Then the assembly is assembled according to the diagram in Fig. 6,6. The VD4D diode is soldered instead of a jumper connecting pin 4 of connector X2 and pin 3 of connector X6. Contacts 1, 2 of the installed connector are connected to the corresponding circuits of the remote control module. As a result, the CDS is synchronized and the internal amplifier of the 3H TV is powered.

A X2 connector is installed on the cross-board of the radio channel module, if, of course, it is not available. Next, connect pin 9 of the XZ connector with pin 2 of the X4 connector (power supply for the UPCHZ), pin 6 of the HZ connector with pin 9 of the X16 connector (volume control), and pin 1 of the X521 connector - through the KD10A diode (anode to this contact) with pin 2 of the connector XXNUMX (APCG).

Connector X19 "Tape recorder" of block A9, which serves to connect a stereo amplifier, is unsoldered as shown in fig. 6, c. In this case, on pins 1,3,5 there will be a sound signal (KSS), and on pin 4 - the volume control voltage. Accordingly, the input connector of the stereo amplifier must also be soldered. In the author's version, the TDA1524 chip is used in the input stage of the amplifier, and the TA7343 chip is used in the stereo decoder.

You can use brightness, contrast, and saturation control voltages to control timbres and balance.

Structurally, the device is made on two printed circuit boards of one-sided foil fiberglass. The drawing of printed conductors and the arrangement of elements on the board of the control module are shown in fig. 7. Connectors XS4 and XS2, as well as XS1 and XS5 are made in pairs in one block. The XS3 connector is selected with the position of the contacts parallel to the board, so the VHF radio receiver board, when connected to it, is a continuation of the control module board.

A drawing of printed conductors and the placement of parts on the board of the switching module are shown in fig. 8.

An L-shaped plastic panel (dimensions: width - 90, height - 25, depth - 10 mm) is installed on the control module board, on which MP7 microswitches - buttons SB1-SB3 with capacitors C3 (on SB1) and C4 (on SB2). Plastic cubes are put on the leads of the LEDs, and the leads themselves are bent to the sides at a right angle. When each LED is pressed, the cubes act on the microswitch stem. The module is inserted into the front panel of the TV instead of the USU-1-15 tuning unit.

The DR and switching modules are fixed on the side wall inside the TV near the network input.

Power modules are small and are, as mentioned, in square-shaped electrical outlets. They are connected to the device through miniature plugs. Three sockets - two for the load and one network for the TV, are combined into one block.

In the device, instead of transistors KT315G and KT3102V, you can use any low-power silicon transistors. Instead of KT814B transistors, transistors of the KT816 or KT837 series are applicable, preferably with a minimum collector-emitter voltage drop, for example, KT837F.

Connectors use the same as in TVs, they do not represent a shortage.

The device does not need to be adjusted. It is only necessary to equalize the signal levels 34: on the TV with the resistor R11 of the radio channel block, as well as the corresponding controls in the external stereo amplifier and in the VHF radio receiver, so that there are no volume drops when switching modes.

The TV uses SDU on the INA84C641NS-168 processor. The control signal for turning on the device is transmitted from the processor through a microcircuit, at the output of which an open-collector transistor is installed. In SB mode, the transistor is closed. The AV signal has a level of about 5 V, the TV signal is 0. The remote control is RC-6.

Now we need to say about the VHF radio. In the author's version, the simplest receiver for the VHF-2 range (88 ... 108 MHz) was used on the K174XA34 chip, assembled according to a standard scheme. It provides direct tuning, that is, increasing the tuning voltage rebuilds the local oscillator up, towards higher frequencies. The antenna is a piece of wire about 40 cm long, located inside the TV.

All the switching voltages of the sub-bands are output to the connector for connecting the receiver, so the radio receiver can be made multi-band. The purpose of the connector pins is clear from their designation. The power supply of the radio receiver can be 5 or 12 V. Depending on the required supply voltage, connect a jumper (P1 or P2) to one or the other pair of contacts marked on the printed circuit board of the control module.

If the TV has an SDU that allows you to manually tune in and memorize stations, then the APCG output of the remote control module can not be connected. In this case, the AFC of the receiver itself will work.

It should be borne in mind that the tuning voltage in the author's version varies from 0,5 to 10 V. Therefore, it is necessary either with a voltage divider or a capacitor connected in series with the varicap to set the boundaries of the received VHF range.

In addition, in the version of the author, the CDS is made according to the simplest scheme, i.e., without a stop channel, and a constant voltage of +5 V is applied to the IDENT input of the processor. Also, the device does not have the ability to manually tune with memory, so the radio receiver is supplemented with a station capture simulator, assembled according to the diagram in Fig. 9. Resistor R2 sets the best sound quality when capturing a station.

The receiver board is fixed on a piece of a unified circuit board, to which the necessary contacts are soldered for connection with the XS3 connector of the device control module. On the same circuit board, the details of the capture simulator are soldered.

Author: G.Alekhin, Donetsk, Ukraine

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