Troubleshooting and Diagnostics Flashcards
7 cards from real CET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Troubleshooting and Diagnostics flashcards as text
A technician observes 60 Hz hum on an audio amplifier output with no input connected. The most probable cause is:
Answer: Power supply filtering capacitor failure or ground loop
60 Hz hum typically originates from inadequate power supply filtering or a ground loop coupling AC line frequency into the circuit.
When an IC chip becomes unusually hot during operation, the first diagnostic step should be:
Answer: Check for correct supply voltage and verify no output is shorted
Verifying supply voltage and checking for output shorts identifies whether the IC is being forced to dissipate excessive power.
A MOSFET gate-to-source resistance measures near-zero ohms. This indicates:
Answer: The gate oxide has broken down, creating a short
The gate-to-source path should be very high resistance; a near-zero reading indicates gate oxide breakdown.
In troubleshooting, the term 'sneak path' refers to:
Answer: An unintended current path caused by component failure or design error
A sneak path is an unintended circuit path that allows current to flow in unexpected ways, often causing erratic behavior.
After replacing a faulty component, best practice before applying power is to:
Answer: Verify the replacement part orientation, check for solder bridges, and confirm polarity
Visual inspection for correct orientation, polarity, and solder quality prevents repeat failures caused by installation errors.
A crystal oscillator circuit fails to start oscillating. After confirming the crystal is good, the next most likely suspect is:
Answer: The feedback network capacitors (C1 and C2 in Pierce oscillator)
The Pierce oscillator requires correct feedback capacitor values to sustain oscillation; wrong or failed caps prevent startup.
A technician reads 12V at the input of a 5V linear regulator but only 3.8V at the output under load. The most likely fault is:
Answer: The regulator IC is failing or overheating into thermal shutdown
A linear regulator producing below-nominal output under load is typically failing internally or entering thermal shutdown due to overheating.