Troubleshooting a dead interconnect — best tool choice An output gate drives four input gates on different ICs. Power is present; the source gate shows a valid pulsing signal on the oscilloscope, but the interconnecting node shows no signal. Which instrument best helps isolate the open/short location along the PCB trace?

Introduction / Context:
When a driven node fails to show the expected waveform, the cause is often a physical interconnect issue (open trace, short to a rail, or a loading fault from one of the receiving ICs). Selecting the correct diagnostic instrument reduces time-to-fix dramatically in hardware debug.

Given Data / Assumptions:

• Power rails are verified OK with a DMM.
• Source gate output pin shows a pulsing signal on the scope.
• The shared node that fans out to four ICs shows no signal.
• Loads are on different IC packages (possible single-IC fault).

Concept / Approach:
A current tracer is used with an injected stimulus to follow current along a PCB trace, revealing where the signal is being sunk, shorted, or interrupted. It excels at locating physical faults like opens or shorts that a logic probe or analyzer cannot spatially localize. An oscilloscope confirms waveforms but does not pinpoint where a trace breaks under conformal coating or inside vias.

Step-by-Step Solution:

Verification / Alternative check:
Temporarily lifting individual load pins can corroborate a single-IC loading fault, but the current tracer provides the fastest physical localization.

Why Other Options Are Wrong:

• Logic probe: indicates logic levels at a node but cannot localize faults along a trace.
• Oscilloscope: already used; it confirms the absence of signal at the node but not the location of the break.
• Logic analyzer: captures bus timing, not physical fault location.

Common Pitfalls:
Assuming a chip failure without verifying interconnect integrity; overlooking hairline cracks or solder bridges between boards and connectors.

Final Answer:
Current tracer