CST Maintenance and Troubleshooting 3 — Questions and Answers
Question 1: A camera shows a strong horizontal rolling bar across the image. This artifact is most commonly caused by:
- Ground loop interference (Correct answer)
- Incorrect white balance
- Overexposed iris setting
- Packet loss on the network
Correct answer: Ground loop interference
Ground loops create a potential difference between equipment grounds, inducing 60 Hz hum that appears as a rolling horizontal bar on analog video.
Question 2: When troubleshooting an IP camera that intermittently drops from the network, what is the correct first diagnostic step?
- Replace the camera immediately
- Check PoE switch port utilization and power budget (Correct answer)
- Reconfigure the NVR's recording schedule
- Update the camera firmware
Correct answer: Check PoE switch port utilization and power budget
Intermittent dropouts on PoE cameras often result from insufficient power budget or switch port overload, which should be verified before other steps.
Question 3: A technician is cleaning camera domes on a quarterly maintenance visit. Which cleaning agent should be avoided?
- Distilled water
- Isopropyl alcohol (70%)
- Ammonia-based glass cleaner (Correct answer)
- Microfiber cloth only
Correct answer: Ammonia-based glass cleaner
Ammonia-based cleaners can cloud polycarbonate dome covers over time, permanently degrading optical clarity.
Question 4: An NVR shows 'HDD Not Detected' after a fan failure event. What is the most likely explanation?
- The NVR's firmware corrupted the partition table
- Overheating from the failed fan caused the HDD to shut down or fail (Correct answer)
- The video codec changed automatically
- A camera's IP address conflicted with the NVR
Correct answer: Overheating from the failed fan caused the HDD to shut down or fail
Fan failure leads to thermal overload, which can cause hard drives to power down or suffer permanent damage from excessive heat.
Question 5: What does a 'video loss' alarm on a DVR typically indicate in an analog camera system?
- The DVR's hard drive is full
- The camera has lost power or the coax connection is broken (Correct answer)
- The camera's night vision IR has failed
- The DVR firmware needs updating
Correct answer: The camera has lost power or the coax connection is broken
A video loss alarm triggers when the DVR detects no sync signal on an input, most commonly due to camera power loss or a severed coaxial cable.
Question 6: Which of the following best describes the purpose of a surge protector on outdoor camera installations?
- To boost signal strength over long cable runs
- To protect equipment from voltage spikes caused by lightning or power surges (Correct answer)
- To convert AC power to DC for the camera
- To filter RF interference from nearby radio transmitters
Correct answer: To protect equipment from voltage spikes caused by lightning or power surges
Surge protectors clamp transient voltage spikes, preventing damage to camera electronics from lightning strikes or power line surges.
Question 7: A camera's image is sharp in the center but blurry toward the edges. This defect is called:
- Barrel distortion
- Field curvature or vignetting (Correct answer)
- Chromatic aberration
- Pincushion distortion
Correct answer: Field curvature or vignetting
Field curvature causes the focal plane to be curved rather than flat, resulting in sharp center focus but blurred edges on a flat sensor.
CST Maintenance and Troubleshooting 3
A camera shows a strong horizontal rolling bar across the image.
This artifact is most commonly caused by: