أعطال أجهزة التحكم عن بعد .. كتاب التلفزيون الملون والعادي

22 - 19 Malfunctions of remote controls:

A - Devices with ultrasound waves: When the ultrasound waves are generated mechanically, the probability of a malfunction in the transmitter is somewhat weak, but if these waves are emitted by a transistor oscillator, the greater possibility is that the battery voltage is weak or lacking, so there is no difficulty for the consumer to replace it. Then the malfunction could be in the circuit of the device.

If the control signal is a modified RF radio signal, it is possible that the defect exists in any part of the circuit after verifying the battery voltages and their safety.

There is a technical way to detect the work of the transmitter circuit and send frequencies. It is in placing an AM radio device on one of the frequency harmonics - next to the transmitting device for control, then pressing the control buttons one after the other. Hearing the sound of the control signal on the radio indicates that the device is working properly, but if one of the control buttons is not working and the rest are working, then this eliminates the possibility of a malfunction in the radio. The transmitter or receiver control device, and it is likely that there is a defect in the circuit elements that do not work.

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ ​But if all compressors do not work, the most likely is the presence of a defect in the transmitter or receiver, and the first step that must be followed is: Examine the source of supply and operating efforts in the same way as usual.

It is possible to track and detect malfunctions of the receiver for control signals that operate on ultrasonic frequencies in the same way as to detect malfunctions of audio amplifiers. Remote control receivers are designed using the tuned radio frequency (TRF) method, and the faults include the RF circuit and the sound generators.

. Infrared devices: We have mentioned that the infrared control system emits distinct modulated pulses for each modulated function with its carrier frequency (42 kHz), and the infrared sensor element captures the signal and then amplifies it through several stages and then applies it to the computer synthesis system.

Faults in the remote control system can occur due to a faulty transmitter or receiver. The oscilloscope is the most useful in detecting faults and locating them. If all the control functions do not work, replace the batteries from the transmitter unit with good and new ones. If it still does not work, an oscilloscope should be connected to the output of the infrared sensor (IC1101) in the diagram. And we press the button (R-9) after the transmitter is about three meters away, and a signal with a voltage of approximately (1) volts from peak to peak (CP-P) appears on the screen and its frequency is (42 kHz) - it is preferable to correct the direction of the transmitter to give the greatest signal on The appearance of this signal makes it possible that the fault is in the receiver control system, and if it does not appear, then the fault is in the transmitter or in the infrared sensor group, or in both sections.

If the fault is in one or more of the control functions, the fault may be in the transmitter.

Transmitter faults:

If all control functions do not work and the battery is good, we proceed to detect the fault as follows:

Connect socket (10) to (1) on the oscilloscope to the infrared transmitter diode anode - set the horizontal speed to (20ms) and the vertical deviation to (50) and press the plunger (R-9). The signal must then be (1) 7 from the peak to the peak of the frequency
(42 kHz) and a full turn (24US). If the carrier frequency and amplitude are correct - switch the oscillator's horizontal position to (10) ms and press the plunger (R-9) several times - modified pulses must be observed when pressing the plunger - then the sensor group circuit The infrared receiver is faulty.

Receiver malfunctions:

When noting reference (17) from top to top
(42 kHz) In the previous test - at the output of the infrared sensor - so move the oscilloscope socket to the anode (D1101) (Fig.) and the horizontal remains in its position 20ms - and the vertical must be set to (0.2V) Place the transmitter about 30 cm away from the sensor Infrared . and press the plunger (R-9), the signal (42 kHz) should be at this point about (6) peak to peak If one or more control functions are not working (not all functions) - connect oscilloscope socket (10) To (1) to the base of transistor 1101 (as in Figure 19-35) - the horizontal position on (10) ms and the vertical on (50mv) - the pulse pattern must appear every time we press the transmitter's button, if the pulse pattern does not appear when pressing One or more staplers - Lift the battery and test for continuity across the contacts of the staplers, if continuity is good when the stapler is depressed. There is a suspicion of (IC1101) or its oscillator components.