In this episode Shahriar examines the failure of a Siglent SHS810 100MHz 1GS/s portable oscilloscope and multimeter. The instrument’s multimeter inputs are functional, however the neither of the oscilloscope inputs display the correct waveform. The displayed signal varied largely as soon as a coax cable is connected and the instrument is powered from an external signal source. This hints to a grounding problem. Further examination of the probes also shows large damage to the ground pads from a possible high-voltage short circuits through the shared ground between the scope inputs.
The disassembly of the unit reveals heavy damage to the ground PCB traces of the input channels. After thorough cleanup of the PCB, the ground traces are repaired using copper tape. The new ground plane corrects the problem and the scope can now be used to measure RF signals correctly.