Why do PCB's fail?
Functional failure of components, Improper operation, variation of power, environmental conditions, component ageing, and damage to PCB tracks are some of the common reasons of PCB failure.
Survey indicates that normally most of the new systems breakdown within the first ten years.
What are normal faults encountered in a PCB repair environment?
Functional IC failures, loaded power supply, input/output pins shorted to VCC or ground, multiplier shorts, faulty de coupling capacitors, Bus faults, Fan out faults, Open/Short of passive devices, Track shorts/opens are some of the most common problems encountered in a PCB.
The trouble with doing something right the first time is that nobody appreciates how difficult it was. -- from "Fortunes"
Conventional methods and its limitations.
Service engineer uses various methods and tools of testing which include conventional equipment's like Oscilloscopes, Multi meter and logic analyzers. General testing Out-circuit testing is performed which may either require the PCB to be connected to the original circuit / equipment so as to get the necessary input signals. This way the whole / entire equipment is required for the testing and may become cumbersome.
Another conventional method needs to remove the PCB and test the components separately. This may cause some major damage as removing and re-soldering has to be done and even the PCB tracks as well as components may get damaged.
How we at HS Electronics are different?
In order to avoid all the above-mentioned problems we in our labs try using new methods. Our methods are the in-circuit testing ones, which do not require removing any components from the PCB. Moreover we at our labs use an intelligent in-circuit tester that tests the PCB at component level. It stimulates appropriate inputs to a device, measures its output response and declares whether it is functionally good or bad. Even complex natured LSI and MSI IC's are tested and the process is less time consuming with good results. Here we can repair the PCB's even with out circuit diagrams | 
