REPAIR OF IMPORTED CDS

REPAIR IMPORTED CDSIf you find that the remote control system (CDS) import the TV starts to fail, the first thing I usually replace a power supply in the remote. However, it is unlikely that the performance of the system was then restored fully and permanently. Often TVs continue to “act up”: require precise aiming of the remote, not controlled from great distances, do not work with the first button push…

 
Nervous, of course, not worth it. As in other everyday situations, it is necessary to perform fault and right to choose the method of their elimination.
 
Thus, the panel [SDU]. It has to be checked by measuring the voltage when any button is pressed (but without removing the batteries from the compartment!). You should also make sure that the voltmeter does not jump at any of the switches on the remote.
 
Further, if the batteries working, the next test an infrared diode of the remote. In most cases it is enough to look at it through the viewfinder included camera, as it captures the infrared radiation. Naturally, this is done whenever the button is pressed on the remote.
 
In the absence of video camera working infrared emitter you can find out by measuring the voltage on the diode tester or a voltmeter in a scale with a measuring range up to 5 V. However, for this you will have to disassemble the remote.
 
If the signals at terminals infrared diode no, you should not suspect a faulty microprocessor controller. As practice shows, it is unlikely that the unit can fail from voltage to 3 volts. But on the quartz resonator, which are designated 20 and located in the yellow rectangular case next to the diode, it is necessary to pay close attention. Particularly the serviceability of its conclusions and the quality of installation.
 
According to the experts, repair shops, a quartz crystal resonator most often fails from mechanical vibrations. So we must be prepared, if necessary, replace with a known good suspicious ZQ. And contrary to popular belief remember: all attempts to find such responsible radioelement replacement of those capacitors are doomed to failure.
 
To the word as possible it is necessary to thoroughly clean an alcohol based solution of the contact pad and corresponding surface of the remote control buttons. Sometimes this is enough to restore his health.
 
However, after such repairs, it may be that the TV is still unwieldy. In this case, as they say, is for specialists.
 
But if the viewer, deciding to further independent search and rectification of defects, preparing to remove the back cover imported TV, then appropriate, perhaps, to remind one very sophisticated device, adapted to repair in primitive conditions. This warning is useful not only because of the complexity of the circuitry used by foreign firms-manufacturers of electronic equipment, or for reasons of electrical safety (in this sense, the imported TV no trickier any domestic), but also because in today’s complex and rather thin PCB network conductors are often side by side near the microprocessor. So, with a careless swipe of possible damage to the equipment even professionals.
 
And last warning to those who still intend to explore the e-maze of imported TV with SDU: not to be trusted off condition of the TV and be sure to unplug the plug from the socket. And later inattention and haste is not necessary, because you should all thoroughly understand, to emancipate the wiring harness and deploy fee to have access to an IR receiving diode.
 
REPAIR IMPORTED CDS
 
Take, for example, AKA TV with built in VCR and combined control, which over time decreases the sensitivity. Next to foster the IR diode it easy to find the most likely to fail elements of the circuit: the transistor in the base circuit which is receiving the IR-diode, the collector load in the form of a resistor Rx with the signal output by the microprocessor.
 
Once we agree that transistor to replace won’t — he, as a rule, good, and Patriotic KT315 in its place will not work. However check, if the base of the transistor taken from the control signal. It is possible to detect even a simple tester. For greater clarity, to use the device better, not in the mode of the voltmeter and in the “х1к” provided for the measurement of resistances up to 1 kOhm.
 
And what do we see? The collector of the transistor the signal is much larger than expected from the tracking circuit to the microprocessor. What’s the matter?
 
Think about the signal levels in digital microelectronics. Even the log.0 is not strictly equal to zero, and varies in the range of values from 0 to 0.4 V. a Similar story with the log.1, it is also its limits.
 
In our case, the level of the pulse signal is not always “up” to the value of the log.1, because the change may bring only a minor positive effect.
 
The illustration of the above can serve as the graphs of the variation of the voltage at the collector of the transistor in the receiving node IR control TV (Fig. 2A). Here Ek is the DC voltage level at the collector of transistor IC — voltage pulse signal. The problem has a simple solution: reducing the resistance of the resistor RX in the collector circuit, raise the voltage EC, and the background voltage of the pulse signal IP is much higher (Fig. 2B). This will allow to overcome the lower threshold value log.1 and to raise the reliability of the circuit operation is already regardless of the direction of the remote on the TV, the distance between them and the charge of the batteries.
 
For the implementation of said solder-in resistor Rдоп a 1 kω resistor in parallel with the side mounting load RX (Fig. 1), without going into the interpretation of nominal value R’s (he applied color labels). And that’s all. Check the operation of the CDS, switch off the equipment from the network and carefully collect the TV.
 
It is useful to notice that the TV could not be included in the network, if familiar with the methodology used by maintenance professionals. Its essence is applying to the transistor node receiving the infrared control “tuning” of 5 V from external source of electricity. Of course, with the correct polarity and temporary watering of the corresponding output resistor RX from the circuit. But this is when you need to measure the signal level. In the simple case, it is sufficient to solder Rдоп without any prior inclusions and checks requiring the filing of utility power.
 
Vladimir SILCHENKO, Tyumen region.

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