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Fixing a Hand Remote Control that doesn’t work!

December 4th, 2011 Leave a comment Go to comments
    It is hard to imagine a television or a multimedia system without remote control now a days. Broken remote control units is an eternal problem. Thanks to China for dumping remote control units, which makes the cost of them affordable between 60-75Rs for television units. But, finding a replacement for multimedia systems is still a problem as no vendor is holding such stocks for its lower sales.
     I have been hit for the same problem when my Altec Lansing 5.1 multimedia system’s remote control broke. In the sense, the remote was functional intermittently. And some time, the key pad mapping got goofed up with + working as – and so on. When I visited my local electronics stores guy, he said the general problem for intermittent remote operation is a conked up crystal that is found inside the remote control unit. 

    Remote control units work with Infrared light communication between the hand-unit and the multimedia system’s base unit.  Commands from the keypad are converted to IR signals, which are received and decoded by the base unit to perform appropriate function.  Since IR light is not visible to human eye, one should use a Camera eye to see the IR light.  The easiest way is to observe the LED mounted in the front of the hand unit through a mobile camera or any camera that’s in working condition.  The cameras bandwidth covers IR and UV apart from the visible spectrum.  You will find that the IR led blinks (carrier frequency is 22khz), when you press any button on the remote control unit.  If you observe that for some keys the IR led is not flashing or intermittently flashing, you may associate the problem to a faulty crystal in the remote control PCB.

    When the remote is opened, you will see a PCB like the one in the picture.  The PCB could be plucked out from the casing by hand.  You will also see a rubber like buttons which are the actual buttons that you press.  The rubber button is placed on the PCB, where the button presses are converted to switching action.  Remember, the buttons will have a conducting coating under it, which indeed closes the circuit when the button touches the PCB. 

    The crystal that comes as a part of the circuitry is shown in the picture.  It is otherwise called a ceramic resonator, which is the crucial component of an oscillator circuitry.  Crystals are typically used against LC, RC tank circuits for its very high stability feature against temperature and humidity. My remote uses a 455Khz crystal named CRB455E (http://dalincom.ru/datasheet/CRB455E.pdf). The cost of this crystal as on today is Rs 2 in Chennai/India.  After replacing the crystal, my remote is working perfectly so far.

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