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Electronic Theatre Controls Inc

Sensor Dimmer Rack Flickering Due to Airflow Issues


Seeing flickering in a rack. Could this be due to an airflow problem?


Yes it can. The rack can get caught between system ok and airflow error. This can cause flicker.  If all of the dimmers that are active in the rack always flicker out together, airflow could be a factor.  If they change at different rates or times, airflow is not a likely culprit.

A few things that can be done to fix the problem:

  • Verify that there is nothing obstructing the fan(s) (on the top of installation racks; on the back of portable packs; on the bottom of touring racks) or blocking outgoing airflow.
  • Open the front door and remove the black filter.  Ensure that it is clean and fairly dust free.  If it is not, clean it.  If water is used during cleaning, do not reinstall into the rack unless completely dry.
  • If on a CEM Classic: 
    • At the CEM press and hold the clear button for 5 seconds.  This will clear the error. 
  • If on a CEM+: 
    1. At the CEM+ press [-] until you see "Press Enter to view rack errors" displayed on the LCD.
    2. Press [checkmark] to enter.
    3. When the errors are displayed, press [checkmark] to clear each one.
    4. Repeat until all errors are cleared.
  • Check back later and see if the error has returned.
  • If the issue returns, try blowing out the control module using canned compressed air by the following instructions:
    1. Turn off power to the rack. This is most commonly accomplished by finding a labeled electrical disconnect nearby and pulling the handle to the off position.
    2. Remove the control module from the rack:
      • On a CEM Classic, slide out the center tab. Grasp with the thumbs and forefingers of both hands and wiggle the module out toward the front of the rack.
      • On a CEM+, gently push on the latch at the bottom of the rack where the triangle indicates. Hook a finger into the handle once it extends from the rack and wiggle the module out toward the front of the rack.
    3. While wearing safety glasses and following all safety procedures detailed by the canned air manufacturer, use canned compressed air (like that often used for computer maintenance) to blow dust off of the circuit boards and out of the module. Pay specific attention to the front right side since the airflow sensor is located in that area.
    4. Reinstall the control module into the rack with firm pressure.
    5. Re-power the rack.
    6. Clear out any errors as detailed above for your appropriate control module.

If these things do not seem to correct the problem, contact ETC Technical Services.

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