Saelig Company Inc. 71 Perinton Pkwy Fairport NY 14450 USA
PCB Fault-finding
Visual inspection is a vital first tool in PCB debug. This is where the SAE106S will become a valuable tool.
Searching for missing or charred components, bad solder joints, and solder bridges is the first order of business
when a bad board comes in for repair. Look for solder whiskers between pads or solder joints. Look for solder
bridges, especially between the pins of fine-pitch SMD chips (but note that adjacent ground pins will often be
bridged by design). If the problem is a short, there may even be burned spots on the printed circuit board. They
can be quite small but will be dramatically discolored brown instead of the normal green solder mask. If there are
multiple boards with the same issue, a common burned PCB can help narrow down the specific location. Using a
benchtop power supply with current limiting can be used power a PCB with a short without doing further
damage. Using freezer spray can identify a joint that is heating up due to a short circuit. Before connecting the
power supply to your circuit, set the supply's voltage to what your circuit requires, and set the current to be a bit
more than the design spec. The power supply will drop the voltage to keep the current at the set value.