The Determination Of The Fault Location Of The Remote Receiver
Once the remote control receiver circuit is not working properly, the following methods can be used to distinguish which part of the fault from the circuit, that is, from the high-level, ultra-upgrading circuit or amplification, shaping circuit.
① Check the amplification, shaping circuit, the signal of the sender/output point is the key point to find the fault. The specific method is to transmit signals with the remote control, the oscilloscope to observe the amplification, the shaping circuit has no signal input (such as LM385F's feet), such as signal waveform, indicating high-frequency circuit, ultra-liter circuit is basically normal, failure in amplification, shaping circuit; If the signal is not measured, the fault is before the ultra-liter circuit: the amplification, the plastic circuit inspection, can measure the LM358 pin voltage, and the normal control, if abnormal, many for the IC itself damage.
② to the ultra-liter circuit overhaul, can first check the transistor DC voltage, if abnormal, check the DC bias circuit or transistor itself. After the DC bias voltage is normal, then check the AC feedback circuit, and the patch capacitance is best checked by substitution method.
The overhaul of high-frequency amplifier circuits, also take the first check the DC work point of the high-level tube after the coupling element method, generally not difficult to find fault components.
Remote control receiver because T is in low voltage, small current situation, generally does not appear burned circuit board failures, transistors and IC damage rate is not small. The highest failure rate is the receiving frequency offset, mostly because the water or circuit board damp causes the ultra-liter circuit to stop oscillation. To do more cleaning, flooding work, multi-measuring voltage (waveform), as little as possible to dismantle components. The receiver of the automotive anti-theft system, whether it is the modulation or the adjustable capacity, whether it is a discrete direct plug-in or SMD device or a mixture (blocking components with patches, transistors, integrated circuits, electrolytic capacitors with direct plug-ins, they are almost entirely interchangeable, as long as the GND (grounding), +V (Power), out (signal output) of the correspondence between the end of the receiver and adjust the receiver frequency can be.