This is just an additional idea to some of effective ideas given by famous administrator of this website like Sir Jestine Yong. I have not yet read this kind of technique. But I had been practicing this for a long time and found to be fast and effective.
I am not really an expert repairer but I repair lots of board with shorted SMD components like cellphones, laptops, testers, portable tv with dVD players, and other electronics equipment and boards which are using SMD components. The SMD components boards are now common in the markets, because most technicians, designers and inventor believed that “SMALL IS POWERFUL”. But what if these equipment have intermittent problems? After the repairer had replace some components and reinstalled the software, he will just return the device and advice the owner to replace with a new one if the problem still exist and suspected that the main board is defective.
I have received cell phones with the same cases, restart problems and a little short or leakage. Most of them came from the hands of technicians. Following the protocol of cellphone repairing techniques, problem still exist due to a little short. Now, it’s time to apply our knowledge here in electronics.
To find for shorted component, clip the red test probe of the analog meter to the ground of the board while the black test probe to the B+ or positive. This is more applicable to Battery operated devices.
Here you can see a reading with little short. Most likely about 200 ohms or above. This was cause of water damage, over charging or an overused device. Pulling out all the suspected IC will give a risk to the repairer because some IC’s are sealed and it needs to reprogram again and IMEI (International Mobile Equipment Identity) or serial nos. maybe lost.
Of course, the first step is to clean the SMD components using soft brush and with cleaning solution if necessary. Then Suspect all the diodes parallel to the battery connector near the power IC, Audio IC, Charging IC and even the CPU IC. To check if the diodes are short, gently pull out each diode using A hot air while analog meter is still attached to + and – terminals. This will only possible if more than two diodes have shorted reading on board which are parallel to battery connector.
Return directly the diodes if there are no changes with the reading to avoid the interchange, this only after checking them individually. Next suspects all parallel capacitors surrounding the power IC, Audio IC, Charging IC, Power amplifier IC, RF IC and even the CPU IC. Without any signs of burned capacitors, it is necessary to do what we did to the diodes. After pulling out each capacitor, using the hot air, glance at the analog meter. If the reading changes to infinity, then that capacitor has leakage and defective. Before returning a capacitor if reading have no changes it should be check individually out of the circuit with ESR METER if necessary, to ensure that defective or another capacitor with leakage may not be returned.
Likewise, if all capacitor are ok then this is the time to decide that board maybe defective after replacing all concerned IC’s and components and of course, including the checking of coils and resistors with the use of BLUE RING TESTER.
With this kind of technique I recommend this is fast and effective rather than checking them on board or with voltage test, because most of the SMD Capacitors have no printed or readable value on it and are parallel in connection. They don’t have even the same capacitance value and have high risk for interchange due to their sizes. This will then result in referring to the unit’s diagram if somebody call our attention and don’t remember their position in which again stolen our precious time.
An expensive cell phones, laptops or portable devices can be repaired through this technique without any expensive repairing equipment.
Without any leakage in the capacitors, it could be still possible to check the defective capacitors but this time it’s the use of ESR Meter. It is the responsibility of the repairer for the accurate ESR reading and computations according to the manufacturer’s guidelines. ESR reading may change every pulling out a capacitor, and is maybe possible to those who will self-study on this.