The TV is turned on and off by the VCR. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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The TV is turned on and off by the VCR. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Телевидение

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There are still many TV sets in operation without remote control systems (RCS). If the owner has a video recorder (VCR) with CDS, it is quite enough to tune his tuner to TV channels received by an antenna or from a cable network, and the TV set to the frequency of the output radio frequency signal of the VCR (or by connecting it via LF), and then it will be possible to switch all programs remotely VM remote control. This is what many owners of VMs with CDS do. But another problem remains: how to remotely turn on and turn off the TV?

This problem can be solved by using the following. When you turn off the VM, the remote control usually closes one of the fairly powerful stabilizers (or electronic switches) in the VM's power supply. Even without a circuit diagram, it is easy to find such a node, remove the turn-off and turn-on voltage from it through a small resistance limiting resistor and apply this voltage to the relay. It is advisable to install a resistor to protect against accidental short circuits. The relay is placed in the TV case by connecting the contacts in parallel to its mains switch. The relay must be used with a relatively high winding resistance so as not to overload the VM power supply. You should also remember to install a diode in parallel with the relay winding (cathode to the plus of the voltage source) to protect the VM from self-induction EMF when it is turned off. As a result, the TV will turn on and off either by its switch or by the relay contacts when the TV is turned on by the button or on its front panel, or on the remote control, as well as by the TV timer.

For example, if the VM "Electronics - VMTs8220" is in use, the REK-34 relay (passport KShch 4.569.009-02, winding resistance is about 470 ohms) can be used, slightly loosening the adjusting spring. The +15 V control voltage must be removed from pin 1 of the CN104 connector located on the cross-board near the "LF Input" socket, and fed through a 27 Ohm resistor with a dissipation power of 0,25 W to a free contact of the SCART connector. The wires going to the relay winding with a diode connected in parallel are connected to it and the common wire contact. Protective diode - KD105B or any similar.

A very long operating time (about 10 years) proved the safety of such a connection for the VM. However, it must be remembered that if you want to record a TV program using the VTR timer, you must remember to unplug the TV from the outlet so that it does not turn on. You can also connect the relay contacts in series with the TV's mains switch, but in this case it will not be possible to use the TV without a VM. In addition, if the TV is connected to the VCR via radio frequency, the first button of the TV program selection block must be set to the frequency of the VTR's output channel, since this button has the priority property when turning on the TV.

Author: A.Ivkin, Istra, Moscow region

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