Cleaning dirty gain controls

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Gain controls, which utilize a variable resistor called a potentiometer (pot) to control the level of the input signal, can collect dust and other particles inside of them. A common symptom of dirty gain controls is an crackling, static, or intermittent sound when adjusting the gain control. This problem can sometimes be remedied by spraying an electronic contact cleaner spray on the body of the potentiometer to enhance electrical contact of the sliding wiper inside the housing of the potentiometer.


Confirm the potentiometer is causing crackling/static/intermittent sound

  1. Hook up the amplifier to produce sound through speakers. See the diagram in Figure 1.
  2. Rotate the active channel’s gain knob back and forth. Listen for crackling, static, or intermittent sounds as the gain control is moved back and forth.



Clean the potentiometers with an electronic contact cleaner spray

  1. Unplug the amp from AC mains power. Remove the amplifier cover. shock.PNG
  2. Locate the potentiometers that control the gain on the amplifier. On RMX amplifiers these parts are located on the front-right of the amplifier. 
  3. Liberally spray the electronic contact cleaner on the body of the potentiometer. QSC recommends DeoxIT® D5 as a contact cleaner.
  4. Move the gain knobs back and forth continuously, at least 20 times. This will ensure lubrication of the internal wiper’s contacts.
  5. Reinstall the amplifier’s cover.
  6. Test the amplifier again for the crackling, static or intermittent sounds.

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Important note: If this procedure does not fix the issue, check all upstream audio devices in the audio system. If all other audio devices check okay, the gain potentiometers may have to be replaced with brand new ones. Please contact a QSC Authorized Service Center for repair options.