CTS AV System Troubleshooting and Maintenance 4 — Questions and Answers
Question 1: A projector displays a green tint across the entire image. After confirming the source signal is correct, what is the most likely cause?
- Faulty HDMI cable with damaged pin 7
- Incorrect white balance or color matrix setting on the projector (Correct answer)
- Lamp nearing end of life causing phosphor shift
- Overheating of the DLP color wheel
Correct answer: Incorrect white balance or color matrix setting on the projector
An incorrect color matrix or white balance setting on the projector is the most common cause of a full-screen color tint when the source signal checks out.
Question 2: During a presentation, audio from a wireless microphone cuts out intermittently. The battery is new and signal strength appears strong. What should be checked next?
- Replace the microphone capsule
- Check for RF interference from nearby Wi-Fi or other wireless systems on the same frequency band (Correct answer)
- Increase the gain on the mixing console
- Switch to a dynamic microphone
Correct answer: Check for RF interference from nearby Wi-Fi or other wireless systems on the same frequency band
RF interference from co-located wireless systems or Wi-Fi networks operating in the same frequency band is a primary cause of dropouts even when signal strength appears adequate.
Question 3: A touch panel control system is unresponsive after a power outage. The panel shows a solid amber LED. What is the recommended first step?
- Replace the touch panel immediately
- Perform a factory reset via the rear pinhole button
- Power cycle the control processor and allow it to fully reboot (Correct answer)
- Re-flash the firmware from the manufacturer's website
Correct answer: Power cycle the control processor and allow it to fully reboot
A solid amber LED on many control panels indicates the processor is offline or initializing; power cycling the control processor is the appropriate first recovery step.
Question 4: An AV technician notices that a ceiling-mounted speaker produces distorted audio only at higher volume levels. The amplifier clip indicator does not light. What is the most probable cause?
- Loose or damaged speaker cone (Correct answer)
- Impedance mismatch between amplifier and speaker load
- Insufficient amplifier headroom
- Incorrect polarity wiring on the speaker
Correct answer: Loose or damaged speaker cone
Distortion that occurs only at higher SPL without amplifier clipping typically indicates a mechanical issue such as a loose or damaged speaker cone or surround.
Question 5: A video conferencing system shows the far-end participants with a noticeable lip-sync issue where audio leads video by about 200 ms. What adjustment corrects this?
- Increase the jitter buffer on the network switch
- Apply audio delay of 200 ms within the AV system's signal processing (Correct answer)
- Reduce the video resolution to lower encoding latency
- Replace the codec with a higher-performance model
Correct answer: Apply audio delay of 200 ms within the AV system's signal processing
When audio leads video, adding an equivalent audio delay through the DSP or AV processor realigns the two streams to correct lip-sync.
Question 6: A laser projector in a large venue suddenly shuts off mid-presentation and displays an error code indicating a thermal fault. What is the most appropriate immediate action?
- Restart the projector immediately to resume the presentation
- Check and clear any obstructions to the projector's intake and exhaust vents, then allow it to cool (Correct answer)
- Replace the laser light engine on-site
- Reduce the brightness setting and restart
Correct answer: Check and clear any obstructions to the projector's intake and exhaust vents, then allow it to cool
A thermal fault shutdown is caused by overheating, most often due to blocked ventilation; clearing obstructions and allowing the unit to cool before restart is the correct first response.
Question 7: After installing a new DSP, all audio signals passing through the unit have a consistent 60 Hz hum. What is the most likely cause?
- Incorrect sample rate setting on the DSP
- A ground loop introduced by the DSP's power connection (Correct answer)
- Clipping in the DSP's input stage
- Phantom power enabled on a non-condenser microphone input
Correct answer: A ground loop introduced by the DSP's power connection
A consistent 60 Hz hum appearing after adding a new piece of equipment is the classic symptom of a ground loop created by differing ground potentials between devices.
CTS AV System Troubleshooting and Maintenance 4
A projector displays a green tint across the entire image.
After confirming the source signal is correct, what is the most likely cause?