CPI Troubleshooting & Fault Diagnosis 2 — Questions and Answers
Question 1: A newly installed HDMI display shows a 'No Signal' error but the source device is powered on. What is the FIRST step to diagnose?
- Replace the HDMI cable immediately
- Verify the display input source matches the connected port (Correct answer)
- Update the firmware on the display
- Check the ambient lighting in the room
Correct answer: Verify the display input source matches the connected port
Mismatched input source selection is the most common cause of 'No Signal' errors before any hardware is replaced.
Question 2: An amplifier produces a loud 60 Hz hum only when audio cables are connected. What is the most likely cause?
- Blown output transistors
- A ground loop between components (Correct answer)
- Incorrect speaker impedance
- Defective volume potentiometer
Correct answer: A ground loop between components
A 60 Hz hum introduced when connecting audio cables is the classic symptom of a ground loop caused by differing ground potentials between components.
Question 3: A touchscreen panel is unresponsive in one corner only. After a reboot the issue persists. What should be checked next?
- Replace the entire display panel
- Inspect the touchscreen ribbon cable for damage or loose connection (Correct answer)
- Disable the on-screen keyboard
- Reduce screen brightness
Correct answer: Inspect the touchscreen ribbon cable for damage or loose connection
Localized touch failure that survives a reboot typically points to a physical ribbon cable fault rather than a software issue.
Question 4: A motorized projection screen stops halfway during extension. The motor runs briefly then stops. What is the most probable fault?
- Incorrect screen gain rating
- Thermal overload protection tripping due to mechanical binding (Correct answer)
- Wrong aspect ratio setting
- RF interference from nearby devices
Correct answer: Thermal overload protection tripping due to mechanical binding
Thermal cutoff triggering mid-travel indicates the motor is drawing excess current due to mechanical binding or obstruction.
Question 5: After running Cat6 cable through conduit, a network switch port shows an amber link light instead of green. What does this indicate?
- The port is operating at 10/100 Mbps instead of Gigabit (Correct answer)
- The cable has correct continuity
- PoE power is being delivered
- The VLAN is configured correctly
Correct answer: The port is operating at 10/100 Mbps instead of Gigabit
On most managed switches, amber link light signals a 10/100 Mbps connection, meaning the cable or NIC cannot negotiate Gigabit speed.
Question 6: A control system sends commands to a projector via RS-232 but the projector does not respond. The cable tests pass. What should be verified?
- The projector's lamp hours
- Baud rate, data bits, stop bits, and parity settings match on both ends (Correct answer)
- The HDMI resolution setting
- The projector's keystone correction
Correct answer: Baud rate, data bits, stop bits, and parity settings match on both ends
RS-232 communication requires identical serial parameters (baud rate, data bits, stop bits, parity) on both the controller and the controlled device.
Question 7: A rack-mounted UPS beeps continuously and displays a battery fault LED. The UPS is only 6 months old. What is the most likely cause?
- Overloaded AC circuits in the building
- A failed or deeply discharged internal battery (Correct answer)
- Incorrect rack mounting orientation
- Exceeding the UPS runtime calculation
Correct answer: A failed or deeply discharged internal battery
Continuous beeping with a battery fault indicator typically means the internal battery has failed or discharged below the UPS's acceptable threshold.
CPI Troubleshooting & Fault Diagnosis 2
A newly installed HDMI display shows a 'No Signal' error but the source device is powered on.
What is the FIRST step to diagnose?