PCB proofing nine small a few common sense you know?
Specific include the following common sense, specific and PCB proofing manufacturers (
Rocket PCB circuit)
1, test PCB should pay attention to the electric insulation performance doesn't allow charged using the iron welding, to confirm the soldering iron does not charged, the best iron enclosure grounding, the MOS circuits should be more careful, can use 6 ~ 8 v low voltage circuit of iron is more safe.
12 blind buried layer PCB circuit board
2, detecting before to understand the working principle of integrated circuit and its related circuit inspection and repair of integrated circuit, first to be familiar with the function of the integrated circuit used, internal circuit, main electrical parameters, and function of each pin pin the normal voltage and waveform and peripheral components of the working principle of the circuit.
If meet above conditions, the analysis and inspection will be easier.
3, it is strictly prohibited in the case of no isolation transformer, use the ground test equipment to reach the bottom of live TV, audio, video and other equipment to detect PCB it is forbidden to use the shell has grounded equipment without the power of the isolation transformer test directly TV, audio, video and other equipment.
Although generally the recorder has power transformer, when exposed to a special especially or larger output power of the nature of the power supply do not know much about TV or stereo equipment, first make clear the machine chassis is charged, otherwise extremely easy and floor live TV, audio and other equipment power supply circuit, spread to the integrated circuit, further breakdowns.
4, test PCB test instrument internal resistance to measure dc voltage IC pin, should choose header Ω resistance is greater than 20 k/V multimeter, or for some pin voltage will have larger error of measurement.
5, to pay attention to the heat dissipation of power integrated circuit test PCB power integrated circuit should be good heat dissipation, not allow to work with the radiator and is in a state of high power.
6, checking PCB board to ensure the welding quality of welding is welded, the accumulation of solder, stomatal cause virtual welding.
Welding time is generally not more than 3 seconds, the iron internal heating type around 25 w power applications.
Has good integrated circuit to take a closer look at welding, had better use ohmmeter measuring ever short circuit between the pin and confirm no solder adhesion phenomenon switched on again.
7, test PCB lead to reasonable for peripheral components added instead of the integrated circuit inside damaged part, should choose small components, and reasonable wiring to so as not to cause unnecessary intercoupling, especially to handle audio power amplifier IC, and between the preamplifier circuit earthing terminal.
8 don't easily conclude that integrated circuit, detecting PCB damage don't judge the integrated circuit has damaged easily.
Because the vast majority of integrated circuits for direct coupling, once a circuit is not normal, may cause many voltage changes, and these changes are not necessarily IC damage caused by, and in some cases measure each pin voltage consistent with normal or close to, also not necessarily can explain integrated circuit is good.
Because some soft fault will not cause the change of dc voltage.
9, testing the PCB don't cause a short circuit between pins voltage measurements or use the oscilloscope probe test waveforms, pens and not caused by sliding or probe integrated circuit short circuit between pins, best in the periphery of the connected directly with pins printing circuit measurements.
Any instantaneous short circuit is easy to damage the integrated circuit, the CMOS integrated circuit in testing flat packaging be doubly careful.
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