Repairing a Printed circuit board or PCB requires board level diagnostics as well as component replacement skills. Without thorough knowledge of its components, diagnosing a problem with a circuit board can be a daunting task. In complicated circuits, one may need a good oscilloscope to probe signals at different points to find problems with circuit components. Once the problem component has been identified, it has to be replaced. In fact, the term "board-level repair" essentially means replacing malfunctioning components with good ones.
1 Identify the malfunctioning component and procure its replacement. In most passive and some active components, such as a voltage regulator, a similar component can be used. However, for an active component with a very specific functionality, such as a high bandwidth audio amplifier chip, the replacement should be the exact same component.
2 Place the circuit board on a flat surface. Tape it to the surface from the sides so that it does not move while you are working on it.
3 Turn the hot air gun on and hold it about 6 inches above the component you want to replace.
4 Pull the component from the board using tweezers; the component should have been loosened by pressure from the air gun.
5 Turn the soldering iron on and set its temperature to 450 degrees Celsius.
6 Put the copper braid on the pads from where the component has been taken out and heat it using the tip of the soldering iron. The excess solder on the pads will be absorbed by the copper braid.
7 Clean the pads and surrounding areas with the alcohol swab.
8 Align the leads of the new component with the pads on board. Make sure that the component orientation is correct.
9 Join all the component leads with the corresponding pads on the board by using the soldering iron and solder.