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How To Repair PCB Circuit Board?

Analysis of PCB failure phenomena

  • Incomplete statistics of the fault parts of the circuit board: The chip is damaged by 30%; the discrete element is damaged by 30%; the connection (PCB plate copper wire) breaks 30%; the program destroys or loses 10% (there is an upward trend).
  • It is known from the above that when there is a problem in connecting the circuit boards and programs, there will be no good boards, also not familiar with its connection. There is not much possibility of repairing PCB board.

Crystal oscillator

  • Usually only the oscilloscope (crystal oscillator need electricity) or frequency meter test, the multimeter can not be measured, otherwise the substitution method can only be adopted.
  • The common faults of crystal oscillator are internal leakage, internal opening, metamorphic frequency deviation, and peripheral capacitance leakage. The leakage phenomenon here is measured by the VI curve of the < tester >.
  • When the whole PCB board is testing, two kinds of methods can be used: in the vicinity of the crystal oscillator, the related chips are not passed, and other fault points are not found except the crystal vibration.
  • There are two kinds of common crystal: two pins,four pins which the second feet is power, attention can not be short

Function and parameter test

  • The detection of the device can only reflect the cut-off area, the amplification area and the saturation area, but can not measure the working frequency and the specific speed.
  • Similarly, for TTL digital chips, only can know the output changes of high and low levels, and the speed of its rising and falling edges can not be detected.

Reset circuit

  • When there is a large scale integrated circuit on the circuit board need to be repaired, the problem of reset should be paid attention .
  • Before testing, it is best to install it back on the equipment, try the machine again and again, and press several reset keys.

Chip with program

  • EPROM chip is generally not damaged, because it need UV to remove chip program, so the program will not damage in the test, but the data said that due to the production of chip materials, with the passage of time (year long) it’s also possible damaged even without use (mainly refers to the program) ,so try to backup the data
  • EEPROM, SPROM, and RAM chips with batteries are very easy to destroy. Whether or not this type of chip has broken the program after the use of the “test instrument >” for VI curve scanning, has not been decided yet. In spite of this, friends are still very careful when they meet this situation.
  • On a circuit board with a battery – based chip, do not easily remove it from the board.

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