(a) the identification of good and bad remote receiver
if the anti-theft system, remote control too close or remote control does not work, you should consider remote control receiver circuit is faulty. determine the remote receiver is working properly, the commonly used methods are as follows.
① the spectrum analyzer receiving antenna close to the receiver, to the anti-theft system (or the remote control receiver) power at 200 ~ 400mhz band should be observed wavy (tuning capacitors) or inverted gaseous (inductance regulation) spectral waveform. if the spectrum analyzer without any response on the screen, indicating that the receiver circuitry is faulty.
② with the remote control transmit signal with an oscilloscope output of the receiver (out), the input of the decoding circuit outputs a pulse signal should be. by sending different data signal, the waveform of the burst width different combinations, such as normal or undetectable waveform waveforms and describe the remote receiver is faulty.
③ remote control receiver with an oscilloscope signal output, with metal objects touch the remote receiver antenna input terminal, an oscilloscope should react more strongly clutter, or explain the receiver is faulty.
④ with the remote transmitter signal with a multimeter measuring dc voltage blocking the signal voltage at the output, when you press the remote control button, its output voltage should change, if no response, indicating that the receiver circuitry is faulty.
(2) remote control receiver to determine the fault location
once the remote control receiver circuit is not working properly, you can press the following methods to distinguish faults from which part of the circuit, that is, from high-level, super and then upgrade the circuit or amplification, shaping circuits.
① check the amplification, shaping circuit, the signal input / output point is to find the key points of failure. the specific method is to use the remote control transmitter signal with an oscilloscope amplification, shaping circuit without a signal input (eg lm385f of ⑤ feet), if the signal waveform, indicating that high-amp circuit, super up another circuit is normal, the fault in the amplification, shaping circuit; such as undetectable signal, then the fault in the ultra up another circuit before: for amplification, shaping circuit checks lm358 pin voltage can be measured, and the normal control, if not normal, mostly ic itself is damaged.
② the super up another circuit maintenance, can check the dc voltage of the transistor, if not normal, check the dc bias circuit or the transistor itself. dc bias voltage is normal, then check the ac feedback circuit for chip capacitors best check with the substitution.
③ high-frequency amplifier circuit maintenance, but also to take the first screening of high discharge tube after checking the dc operating point coupling element, usually is not difficult to find the faulty component.
the highest failure rate is receiving frequency offset, mostly because of water or moisture to make ultra up another circuit board circuit stops oscillating due. car alarm system with receiver, whether it is a sense of style or tone tuning capacitors, but also whether it is discrete chip devices or direct plug-in or hybrid approach between them almost completely interchangeable, just find gnd (ground), + v (power positive), out (output) side of the correspondence relationship and re-adjust the reception frequency to the receiver.