Hunting for Electrical faults
Contents
Background information
Electrical faults can be a result of many factors within a PCB or the device as a whole, but typically failures happen for the following reasons
There are three key steps to initial troubleshooting or triaging a problem
- Does the circuit receive power? - Check, Batteries, fuses,buttions/switches are in the correct order
- Does the circuit power on briefly? - Check Lose/bad connections, missing components, capacitors, transistors, diodes, IC pins are placed corrected, power supply issues
- Does the issue only appear in one area? - Any area overheating, burning smell, smoke
- Multimeter
- Scrapper
- Thermal camera (with screen)
- Device with internet that is able to view schematics
- microscope
Visual damage
Look for any visually broken traces (internal wire), solder connecting two pins together, burn marks, white salt deposits, rust
Water and dirt/dust
If a device as been exposed to the elements, especially for a long period of time build up of minerals and or salt from water can cause shorting of pins, alongside the rust and corrosion that
forms over pads, pins and springs which prevents a stable connection from being made and typically devices being come unrecognized or appearing not to work at all.
In most cases simple removing the build up either through
Shorts or loose connections
These issues may not be immediately visible to the naked eye and may require further inspection under a magnifier such as a microscope, to find small cuts or joints in pins, wiring and or solder joints
In order to locate shorts, you can measure two points either side of the issue (start with the charging port and work your way backwards)see Reading schematics using the device schematic (if available) to find where
the traces lead or simply follow them on the board if possible. Once you have your two points then use a multimeter with a fine tip set to continuity mode to see if the trace is damaged, if there is a beep then there is
continuity(A connection between the two points),
If it does not beep, that means there is a gap in the trace, in order to locate the break, either visually search for damage, or move the non-ground pin of a multimeter along the trace from until it stops beeping, at which point
you have found the break, this requires a bypass using a wire soldered to either side of the break (bridging) to allow for the current to reach the other side, to ensure it works retest with multimeter.
If it now beeps your good to go.
Thermal issues
use of thermal camera to look for "hot spots" that are likely on resistors that have shorted due to the excess current flowing through which creates a build up of heat highlighting it against the thermal background of the rest
of the board
The typical fix for this is to replace the part see use of a hot air gun
Damaged components
Components can be damaged for any number of reasons, including simple failure due to overuse. While annoying and occasionally expensive, damaged components are often the most straight forward fixes,
as, it is often just a matter of replacing the component to restore the device's functionality.
Human error or incorrect schematic/literature
Sometimes things just made incorrectly, either due to poor solder joints that don't make proper contact, or a reversed engineered schematic simply being wrong.
Some issues simply do not have an initial cause, This is an important factor to consider in order to avoid wasting time troubleshooting off an incorrect document
instead of applying your own skills and knowledge to locating the issue yourself.
What tools you will need
Items are not listed in any particular orderRequired
Optional but useful
Step-by-step guide with images
Insert step-by-step walkthrough with images and summary text here
Flow chart of order of operations
Troubleshooting/tips and tricks
Fixes to any common issues that were encountered or could be easily encountered
Related Topics
Topics such as desoldering to chip off or firmware dumping for disk PCB repairs
Further reading
External references in wiki references can just be cited through the keyword link