Most of the current color TV sets, various types of disc players, home theaters and other audio and video devices and air conditioners are remote control types, and they are all infrared remote control types. It is true that the use of infrared remote control technology is very convenient in terms of operation and use. The small and exquisite remote control is flexible and easy to handle in the hand. On the other hand, the remote control is often prone to various failures due to various "tossing", and of course its own inherent reasons. The following is an analysis of the "remote control failure" that is most likely to occur in the remote control. Once the nature and cause of the fault are recognized, the specific maintenance work will be solved.
Second, "remote control failure" fault definition
The remote control failure fault means that the remote control is not sensitive enough to the controlled device, and it is not reliable. Sometimes the control function is normal, sometimes it can barely realize the control action, and sometimes it has no control effect.
Third, "remote control failure" failure analysis
According to my practical experience in researching remote control technology and repairing remote controllers for more than 20 years, I believe that the unit circuits that may cause remote control failures mainly have the following aspects:
1, keyboard matrix unit circuit failure
Since the remote controller is in use, the switching between the functions must be completed by operating the key switch on the keyboard matrix circuit, so the operation frequency of the keyboard is very high, and the failure rate of the unit circuit is relatively high, especially on the button. The conductive rubber is prone to wear and aging, and the aging effect accounts for the largest proportion of remote control failures. The aging phenomenon is mainly manifested by a large increase in surface resistance and volume resistance, followed by cracking and deformation. The aging phenomenon will cause the key interdigitated disc (ie, the key contact) to be effectively turned on. The coded input port of the integrated circuit keyboard cannot effectively identify the key position information of the operated button, and of course it is impossible to output the corresponding function. Remote command signal. When the button is pressed excessively, there is a possibility that the key contact is turned on, and the aging button is occasionally effective.
Another part of the key matrix circuit that is prone to failure is the key interdigitated disc. The early key interdigitated discs are made together with the copper foil lines on the printed circuit board. Because the copper foil is easy to oxidize and rust, and is not very wear-resistant, it is easy to produce poor key contact and insensitive function of the keys. . In recent years, the carbon film printing process has been gradually adopted, which has greatly improved the electrical reliability of the interdigitated discs, and the performance has been significantly improved. However, the process level and quality of the products of various manufacturers are uneven, and some carbons are available. The film strength is poor, the texture of the original carbon film is relatively brittle. When the remote control is damaged or repaired, the fork plate is improperly handled, which is likely to cause damage to the carbon film interdigitated disk and falling off (partial falling off).
There is also a factor that damages the keyboard matrix circuit, that is, some users violently press the button when operating the remote controller for some reason, which is very likely to cause damage to the button conductive rubber and the carbon film interdigitated disc. Moreover, since a part of the printed circuit board is subjected to a certain degree of deformation after being subjected to strong pressure, the printed carbon film line or the copper foil line thereon is also easily damaged. A common phenomenon is that the line is cracked in the cross direction, thereby causing contact. unpleasant sight.
2, the reference oscillation unit circuit failure
In the reference oscillating unit circuit, the ceramic resonator is a wearing member. Violent mechanical vibration, moisture and its own causes can change its resonant frequency. Once this change exceeds the tolerance requirement of the coding IC for the reference oscillation frequency, remote control failure will occur, which will result when the situation is serious. The remote control is invalid.
In addition, when the capacity of the capacitor of the external oscillating network in the reference oscillating unit circuit is reduced, leakage, open soldering, and resistance failure (common phenomenon is resistance increase and open soldering), it also directly affects the oscillation frequency and is directly related to whether it is normal. Start up.
3, infrared emission unit circuit failure
In terms of remote control failure, the infrared transmitting unit circuit is also a frequent fault location. The typical fault is that the infrared light emitting diode pin is loose (referring that the pin is loose at the solder joint), especially the remote control of the infrared light emitting diode exposed installation structure. When the infrared light-emitting diode is subjected to a collision, it is easy to cause the pin to loosen and form a non-connected state. When the remote control receives a large mechanical force (such as beating, heavy pressure or impact), the infrared light-emitting diode will be faulty such as desoldering or cracking of the pad. In addition to the above, the infrared light-emitting diode and the current limiting resistor also cause internal contact failure, and the change of the on and off states is irregular, which will cause the remote control to malfunction.
4, power unit circuit failure
The situation that the remote control unit generates a remote control failure due to the failure of the power unit circuit is common, mainly occurs on the battery circlip. First, the battery circlip has a bad contact with the battery due to rust. Second, the battery circlip The solder joints are loose, and the time is broken. Most of them are caused by mechanical damage to the remote control. Third, the battery leaks, seeps, or a small amount of electrolyte is deposited, resulting in oxides on the positive and negative ends of the battery. It hinders the normal circulation of the current; in addition, it is caused by excessive mechanical force on the battery circlip when the battery is removed and installed. There is also a case where the capacity of the electrolytic capacitor that is responsible for the decoupling of the power supply is excessively reduced, and may even be completely lost, thereby losing its decoupling effect, causing the remote control circuit to generate self-oscillation or critical self-oscillation, which is serious. Remote failures can also occur.
