As the title suggests. I removed the power managment chip already but 3V3 is still shorted to ground.Since the schemtacis arent complete i cant find all caps to test first.Can there be another issue to check first?
2 Answers
There is a device called "positional current probe" This can measure current in a PCB trace without damaging the trace in anyway,it measures the surrounding magnetic field. It is good for upto about 20 amps. Here is a link: https://www.power-mag.com/pdf/feature_pdf/1327592496_TTI_Layout_1.pdf
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Good bit of kit, but blisteringly expensive unless you're a professional HW dev doing this kind of specific thing day in, day out. I do a lot of hw, and have a wide range of other customer scope probes, but still can't justify the investment in this particular part. See my suggestion below for a way to achieve a very similar effect, but just using a sensitive voltmeter.– colintdFeb 2 at 12:17
I've traced powerplane manufacturing faults on new PCBs, by applying a decent current between the planes in questions (say 5A), then using a sensitive volt meter (mV or uV settings) to plot the voltage drop profile between the -ve wire of the PSU, and various places on the plane (use a pin to make contact through the solder mask). You can normally see the voltage drop as you move from the supply to the position of the fault, and once you go past that it is stable. A bit of probing can normally locate the fault fairly closely.
Alternatively, an IR camera can also often show up a hot-spot at the point of shorting.
