Troubleshooting a suspected bad RAM: address and data inputs show pulses; control pins are inactive (held HIGH); outputs probed show Q0, Q2, Q3 dim (floating) and Q1 solid HIGH. What is the most likely fault?

Introduction / Context:
When a static RAM is not enabled (chip-select or output-enable held inactive HIGH), its data outputs enter a high-impedance state. A logic probe often shows a dim or indeterminate indication for Hi-Z lines. A single output that reads a strong logic HIGH under these conditions indicates a fault. This question tests your understanding of tri-stated outputs and failure signatures.

Given Data / Assumptions:

• All address lines and data inputs are active, showing pulses.
• An active-low enable line (for example, OE or CE) is HIGH, so outputs should be disabled (Hi-Z).
• Probe readings: Q0, Q2, Q3 dim; Q1 solid HIGH.

Concept / Approach:
With outputs disabled, every data output should float. A logic probe typically shows a weak or dim indication on a floating node due to leakage or capacitive pickup. A single pin stuck at a solid HIGH while disabled suggests a short or internal latch-up to Vcc on that specific output driver.

Step-by-Step Solution:
Outputs should be Hi-Z when the active-low control is HIGH.Dim indications on Q0, Q2, Q3 are consistent with Hi-Z.Q1 showing a solid HIGH contradicts Hi-Z behavior.Therefore, Q1 is likely shorted to Vcc internally; the chip should be replaced.

Verification / Alternative check:
Power down, measure resistance from Q1 to Vcc. If abnormally low, the pin or driver is shorted. Also confirm behavior persists with the IC removed from the circuit to rule out board-level shorts.

Why Other Options Are Wrong:
Option A and D: Multiple open outputs would not present as a solid HIGH on Q1.Option C: Only partly explains dim outputs, not the strong HIGH on Q1.Option E: Observation does not match a ground short.

Common Pitfalls:
Misreading logic probe brightness and forgetting that disabled outputs are tri-stated, not driven. A single driven level while disabled is a strong indicator of a fault on that pin.

Final Answer:
Q1 output is shorted to Vcc; replace the chip