Semiconductor Troubleshooting MCQ Quiz — Part 5 of 5

A. A short circuit downstream, such as a shorted rectifier diode or shorted output, drawing excessive current ✓ Correct answer

B. The mains supply voltage is slightly lower than nominal

C. The load connected to the supply is drawing too little current

D. The fuse rating installed is higher than the circuit needs

A. Whether every capacitor on the board should be replaced immediately

B. Whether the output connector's plastic housing is the correct color

C. Whether the correct AC input (mains) voltage is actually reaching the input terminals of the supply ✓ Correct answer

D. Whether the transformer needs to be rewound without any testing

A. The capacitor's capacitance value has increased and improved filtering performance

B. The capacitor has failed or is failing internally, likely from overvoltage, excess ripple current, or age, and should be replaced ✓ Correct answer

C. It is safe to continue using the capacitor indefinitely since bulging is only cosmetic

D. This is a normal appearance that indicates the capacitor is performing exceptionally well

A. An oversized transformer supplying more voltage than needed

B. Too many pull-up resistors installed on digital input pins

C. A fuse rated correctly for the circuit's current draw

D. A dried-out or degraded filter/smoothing capacitor with increased ESR that can no longer filter effectively ✓ Correct answer

A. Shiny and perfectly smooth, identical to a properly soldered joint

B. Dull, grainy, or cracked in appearance rather than the shiny, smooth, cone-shaped finish of a good joint ✓ Correct answer

C. Completely black and charred over the entire joint

D. Simply an oversized blob of solder with no other visible difference

A. Replace the entire PCB immediately without further investigation

B. Increase the supply voltage substantially to force the fault to appear

C. Ignore the intermittent fault since it will likely resolve itself over time

D. Gently flex or lightly tap the board near the suspect area while monitoring the circuit's behavior to try to reproduce the fault ✓ Correct answer

A. Touch the highest-voltage point in the circuit before touching the component

B. Work while standing on a thick wool carpet for extra comfort

C. Use plastic-handled tools exclusively with no grounding required at all

D. Wear a grounded antistatic wrist strap and work on a grounded antistatic mat ✓ Correct answer

A. A large visibly charred hole through the component body

B. A completely melted plastic casing

C. A loud audible pop at the moment of failure, every time

D. Usually no visible external damage at all; the device instead fails intermittently or completely without any outward sign ✓ Correct answer

A. Checking whether a complete, low-resistance conductive path exists, such as verifying a PCB track or fuse is not broken ✓ Correct answer

B. Precisely measuring an AC voltage waveform's frequency

C. Measuring the exact gain (hFE) of a transistor

D. Precisely measuring a capacitor's exact capacitance value

A. Deliberately short the mains input terminals together before opening the case

B. Immediately touch all exposed points with bare hands since the supply is switched off

C. Allow adequate time or actively verify/discharge the high-voltage filter capacitors, since they can retain a dangerous charge well after power is removed ✓ Correct answer

D. Assume all capacitors are automatically safe as soon as the mains plug is removed

A. Only the output connector housing needs to be checked, nothing internal

B. The transformer must always need to be completely rewound

C. The mains fuse must always be blown whenever this symptom occurs

D. The regulator IC itself may be faulty, or its output may be shorted by a downstream fault, causing it to shut down or fail to regulate ✓ Correct answer

A. Replace every diode in the circuit as a precaution without ever testing any of them

B. Assume resistance readings on an installed diode mean nothing useful and skip testing entirely

C. Always trust the in-circuit reading fully with the circuit still powered on, since polarity does not matter

D. Measure with the circuit powered off, and be aware that you may need to lift or desolder one leg since parallel components can distort the reading ✓ Correct answer

A. This symptom always indicates the incoming supply voltage is too low

B. Excessive load current being drawn, or the heatsink not being properly attached or lacking sufficient thermal compound ✓ Correct answer

C. A series diode should always be added to fix this specific symptom

D. This symptom always means the fuse installed has too low a current rating

A. It intentionally increases thermal resistance to slow down heat transfer

B. It provides complete electrical insulation on its own, fully replacing the need for a mica or silicone insulating washer

C. It fills microscopic air gaps between the two mating surfaces, improving heat transfer from the component into the heatsink ✓ Correct answer

D. It is applied purely for cosmetic appearance and has no functional purpose

A. Gradual overheating of internal components, potentially leading to thermal shutdown or premature component failure ✓ Correct answer

B. Noticeably improved performance due to reduced acoustic vibration

C. An immediate explosive failure of the equipment the moment the fan stops

D. No measurable effect on the equipment's operation whatsoever

A. The supply voltage to the coil being perfectly stable and exactly at the rated value

B. An unstable or fluctuating coil drive voltage, or a marginal/noisy control signal driving the relay coil ✓ Correct answer

C. The relay coil's DC resistance being too high for the circuit

D. The relay's contacts being permanently welded shut in the closed position

A. Increase the supply voltage progressively until the LED eventually lights up

B. Replace the entire PCB assembly without doing any localized testing

C. Assume the LED itself is bad and replace it immediately without checking anything else first

D. Verify supply voltage actually reaches the LED's circuit, check the LED's polarity, and check that the current-limiting resistor and the LED itself are not open ✓ Correct answer

A. Measure its resistance out of circuit, ideally after desoldering at least one leg, since parallel paths in the live circuit could give a misleading reading ✓ Correct answer

B. Rely on visual inspection alone and never bother measuring its resistance

C. Assume the resistor's value is still correct as long as it is not completely blackened

D. Measure it in-circuit with full power still applied to the board for the most realistic reading

A. This can only ever be caused by using the wrong color wire for the motor connection

B. Nothing further needs investigation; the same replacement part should just be reordered repeatedly

C. Possible causes such as inadequate heatsinking, incorrect or noisy gate drive, unsuppressed motor back-EMF, or the motor drawing excessive current ✓ Correct answer

D. This can only ever be a firmware or software bug and never a hardware issue

A. This is a completely normal and expected power-on inrush current surge

B. The replacement fuse itself must have been defective, and this fully explains the failure

C. An underlying short-circuit or overcurrent fault is still present in the circuit and must be located and repaired before re-fusing again ✓ Correct answer

D. This always indicates the wrong color-coded fuse body was used

A. Use a fuse with exactly the same current and voltage rating and the same type, such as fast-blow or slow-blow, as originally specified for that circuit ✓ Correct answer

B. Use a bare piece of wire or a metal strip bridged in place of the fuse

C. Use a fuse rated for a lower current than the load requires, regardless of its type

D. Use a fuse rated for a higher current so that it stops blowing so often

A. To view the shape and amplitude of the ripple waveform riding on the DC output, revealing filtering or regulation problems ✓ Correct answer

B. To check simple continuity of a PCB track, similar to a multimeter's continuity mode

C. To measure the exact resistance value of a component in ohms

D. To measure a capacitor's exact capacitance value directly

A. It permanently changes the DC voltage level the probe reports

B. It increases the maximum voltage rating the probe can safely measure

C. It disables the probe's ground clip connection for safety

D. It ensures the probe's capacitance is properly matched to the scope's input, so waveforms are displayed accurately without overshoot or rounding distortion ✓ Correct answer

A. Only check the very last stage of the circuit and ignore everything before it

B. Immediately replace every component on the board without any measurement

C. Randomly probe test points on the board with no particular order or logic

D. Check supply voltages and key signals stage by stage from input toward output, such as using a half-split method, to isolate which stage is faulty ✓ Correct answer

A. Always begin testing at the very first component in the entire chain, regardless of chain length

B. Test at the midpoint of the signal chain first, then use the result to narrow the search toward either the input half or the output half where the fault lies ✓ Correct answer

C. Test components in a completely random order with no logical structure

D. Only check the power supply rails and skip checking any signal stages

A. Measure the winding's DC resistance in ohms with the transformer unpowered; an open (infinite/OL) reading indicates a broken winding ✓ Correct answer

B. Measure the winding using the AC voltage function while the transformer is fully powered and energized

C. Transformers cannot be usefully tested with a standard multimeter at all

D. Always apply full mains voltage directly across the winding while probing it with the meter

A. This is completely normal behavior for any healthy transformer under any load condition

B. The transformer's output voltage is definitely too high above its rated value in this scenario

C. Shorted turns within one of its windings, causing excessive circulating current and heating even without much load current being drawn externally ✓ Correct answer

D. There is no meaningful relationship between winding faults and transformer temperature

A. Only check the output ripple with an oscilloscope and never test the individual diodes themselves

B. Apply full mains voltage directly across the module while probing it with bare, ungloved hands for a realistic test

C. Test each of the four diodes individually in the multimeter's diode mode after isolating them from the circuit, desoldering as needed to avoid parallel-path errors ✓ Correct answer

D. Replace the entire bridge rectifier module preventively without ever testing it

A. The capacitor can overheat, vent gas, or even rupture explosively, and reversed polarity must always be avoided ✓ Correct answer

B. The capacitor's rated capacitance value simply doubles when installed backwards

C. The circuit will work perfectly and actually filter ripple more effectively

D. There is no consequence at all, since all electrolytic capacitors are non-polarized by design

A. Clean the contacts with an appropriate contact cleaner and, if necessary, gently re-seat or re-tin the connection before retesting ✓ Correct answer

B. Replace the entire circuit board immediately without attempting any cleaning

C. Apply excessive mechanical force to permanently bend the connector out of shape

D. Ignore the corrosion since it is expected to clear up on its own over time

A. A dry or cracked solder joint, or a marginal/loose connector contact, that changes electrical continuity under mechanical or thermal stress ✓ Correct answer

B. A firmware or software bug is always the explanation for this specific behavior pattern

C. An incorrect component value was definitely installed during original assembly

D. A fundamental design error in the original schematic is always the explanation

A. Power down the circuit and, where applicable, discharge it first, and use proper ESD precautions before handling the static-sensitive component ✓ Correct answer

B. Continue working with the mains connected throughout, for the sake of testing efficiency

C. Hold the IC firmly by its pins without any grounding precautions at all

D. Skip powering down entirely, since it only wastes valuable troubleshooting time

A. This creates a near short-circuit path through the meter, which can blow the meter's internal fuse or potentially damage the circuit being tested ✓ Correct answer

B. Nothing happens because the meter automatically detects and switches its own mode

C. This still gives a correct and safe voltage reading on the display

D. The meter safely displays zero with no other effect whatsoever

A. Check only the external output connector and disregard everything internal to the supply

B. Immediately replace the entire circuit board without checking any individual component

C. Check the rectifier diodes for an open-circuit failure and check the filter capacitor for being open or dried out ✓ Correct answer

D. Always assume the transformer itself must be rewound without further testing

A. The component is definitely internally short-circuited

B. The multimeter itself must be defective and needs recalibration

C. The component, or the connection leading to it, is likely open, and the meter's high input impedance is displaying close to the full source voltage across that open path ✓ Correct answer

D. The component is functioning in a perfectly normal and healthy manner

A. It completely replaces the need to ever measure capacitance at all, for any purpose

B. It is designed only for measuring fixed resistors, not capacitors

C. It can reveal a capacitor that has dried out or aged and shows abnormally high ESR, even though its measured capacitance may still appear close to its nominal rated value ✓ Correct answer

D. It measures the exact voltage rating printed on the capacitor's casing

A. Power off the board and investigate the underlying overcurrent cause before considering reapplying power ✓ Correct answer

B. Immediately reapply full power to see whether the board still functions despite the visible damage

C. Simply replace only the fuse and continue operating the equipment as before

D. Ignore the scorching entirely as long as the board still appears to power on normally

A. Resistance can technically only ever be measured while a circuit is fully powered on

B. It is purely a safety formality with absolutely no effect on measurement accuracy

C. Isolating power actually changes the true underlying resistance value of the component itself

D. Powering off prevents parallel current paths elsewhere in the circuit, and any charge stored in capacitors, from producing a false or misleading resistance reading ✓ Correct answer

A. Only a firmware or software issue should ever be suspected in this exact scenario

B. Components located closest to the mains input, such as the rectifier diodes, a metal-oxide varistor (MOV), or the input fuse ✓ Correct answer

C. Only the final output connector should ever be suspected in this exact scenario

D. Only the display module should ever be suspected in this exact scenario

A. It provides the main DC filtering function for the rectified output

B. It amplifies the incoming AC input signal before rectification

C. It clamps and absorbs transient voltage spikes on the mains input, protecting the downstream circuitry from damage ✓ Correct answer

D. It precisely regulates the output voltage to a fixed value

A. Use any ungrounded iron, since heat from soldering carries no static electricity risk at all

B. Deliberately avoid grounding the iron tip so that static charge builds up for a cleaner-looking joint

C. Use a soldering iron with a properly grounded tip, suitable for ESD-sensitive electronics work ✓ Correct answer

D. Always use the maximum available iron temperature to complete the work more quickly

A. The output voltage will read perfectly clean with essentially zero ripple

B. Increased output ripple and noise, and possibly reduced stability, despite the capacitance reading appearing normal ✓ Correct answer

C. There will be no observable symptom at the load whatsoever

D. The output voltage will roughly double from its rated value

A. Immediately disassemble every stage of the unit and desolder all of its ICs

B. Assume without any testing that the main processor IC has failed

C. Confirm that the unit is actually receiving mains power and that its internal fuse is intact ✓ Correct answer

D. Replace the power switch immediately without performing any testing at all

A. To avoid a serious electric shock hazard, since many SMPS primary-side circuits are directly connected to mains voltage without any isolation transformer ✓ Correct answer

B. So that the equipment's cooling fan does not stop spinning during the test

C. There is no real hazard, since the SMPS primary side is always fully isolated and safe to touch directly

D. So that the meter's continuity-testing function is not accidentally damaged

A. Solder a second capacitor in parallel with the faulty one without removing it

B. Replace it with a new capacitor of equal or better voltage and capacitance rating, observing the correct polarity ✓ Correct answer

C. Reuse the same capacitor since the bulging is understood to be purely cosmetic

D. Increase the circuit's operating voltage to compensate for its reduced effective capacitance

A. Visual inspection of leads is unnecessary as long as the circuit powers on at least once

B. Cracked leads are cosmetic only and can never cause any electrical fault

C. Hairline cracks in a lead always indicate the component's internal circuitry has failed, not the solder joint itself

D. Mechanical stress or repeated thermal cycling can crack a solder joint in a way that is not always obvious, causing an intermittent open connection ✓ Correct answer

A. Measure the joint's capacitance value using the multimeter's capacitance range

B. Apply full mains voltage directly across the joint and observe whether it survives

C. Disconnect the multimeter entirely and rely only on a visual inspection of the joint

D. Measure continuity or resistance directly across the joint while gently applying probe pressure on each side of the joint to see if the reading changes ✓ Correct answer

A. The fuse itself must actually be internally short-circuited despite testing as intact

B. The load connected after the fuse must be short-circuited

C. The supply feeding that point in the circuit is not present, for example due to a preceding open circuit or a missing upstream supply ✓ Correct answer

D. The multimeter's own internal fuse must have failed

A. A resistor and a bare screwdriver have exactly the same electrical effect in this situation

B. Using a resistor recharges the capacitor faster than a direct short would

C. A resistor limits the discharge current, avoiding a dangerous spark or arc while still safely bleeding away the stored charge over a short time ✓ Correct answer

D. Using a screwdriver would actually charge the capacitor to an even higher voltage

A. Supply voltage has no real effect on how digital or analog ICs actually operate

B. All ICs behave identically no matter what supply voltage is actually applied to them

C. Checking Vcc is only ever relevant for dedicated power-regulator ICs, never for logic or op-amp ICs

D. Many apparent faults are actually just a missing or incorrect supply voltage reaching an IC, which mimics a 'faulty IC' symptom without the IC itself being defective ✓ Correct answer

It is for ITI, diploma and B.Tech students, apprentices and working technicians who want to test fault-finding knowledge. The explanations are written to teach the reason, not just the answer.

Attempt the quiz first without looking. Then open the answer key, read the explanation for every question you missed, and retake the part after a day to see whether the explanation stuck.

No, but the parts build on one another: fundamentals first, then components, then circuits and real-world scenarios. Part 5 is the best test of whether you can apply the earlier parts to a live fault.