Logic probe and pulser diagnosis: A probe on a gate's output shows a dim (weak) indication, and exercising each input with a logic pulser does not change the output indication. What fault does this most strongly suggest?

Introduction / Context:
Logic probes typically display HIGH, LOW, or pulsing states, and some indicate a “weak” or indeterminate level with a dim LED. When a logic pulser applied to inputs fails to elicit any deterministic response at the output, a high-impedance or floating node is suspected.

Given Data / Assumptions:

• Probe indicates a dim/weak output level.
• Inputs are individually driven with a logic pulser.
• No output state change occurs.
• Board power and ground are otherwise present.

Concept / Approach:
An “open” output (internally damaged transistor pair or disconnected pin) leaves the node floating. The probe senses neither a firm HIGH nor a firm LOW, resulting in a dim indication. Because the output stage is not actively driving, changing inputs does not propagate to the output node. A genuine tri-state could also float, but it is usually controlled by an enable pin and would be documented; here, the symptom is consistent with an internal open.

Step-by-Step Solution:
Confirm probe ground and supply are good (quick sanity check).Pulse each input; observe no change at output → logic not coupling to node.Interpret dim/floating output as high-Z with no active drive.Conclude: output stage is open; replace the IC.

Verification / Alternative check:
Scope the output; a floating node may show noise pickup. Ohmmeter to ground/VCC with power off may show abnormally high resistance compared to a known-good gate.

Why Other Options Are Wrong:
Low supply would affect many nodes, not just one output, and the pulser would still move levels.

A bad probe ground gives erratic readings everywhere, not reproducible behavior on one gate.

Tri-state requires a disabled enable pin; check OE first, but the symptom here points to damage.

Probe bandwidth limits produce missed pulses, not a constant dim DC indication.

Common Pitfalls:
Forgetting to verify output-enable pins on bus drivers; confirm OE is asserted before condemning the IC.

Final Answer:
The output of the gate appears to be open.