PanelDue 7i- Buzzing noise when brightness is dimmed

  • Hi there 😉
    Yesterday, I received my new Duet Wifi and PanelDue 7i. Today, I uploaded the latest Firmware files to both, the Board and the LCD. As the LCD uses the "Auto-Dimm" function I noticed a strange behavior. As soon as the Panel dimms, there is a really strange buzzing noise. If you switch the brightness to 100% the noise is off. The sound also changes depending on the brightness level… Is there any way to solve this problem or is my panel broken?

    Another question I asked myself as I am testing the panel: Are there any problems with "burning in- screens"? As the panel is always on showing the same screen like for a 10 hours print, isn't this a problem?

    As I am no nativ english speaker, I hope, you got what I meant 🙂

    greetings from gemany


  • administrators

    1. Can you tell whether the buzzing sound is coming from the backlight inverter components at the back of the board (close the the "L2" legend), or from the piezo sounder on the front?

    2. I don't think there should be a problem with constant patterns burning in the screen. We only introduced the dimming facility in the most recent firmware release candidates, and nobody has reported any burn-in. I have been using PanelDue since mid 2014 and I don't see any burn-in, although perhaps I don't have my printers turned on a much of the time as some users do.

    mfg David

  • It seems that the sound comes from the back of the board and is loudest around the LA2- "building" soldered on the back. If I tap my finger onto the piezo sounder the sound doesn't change so I think this is not the reason of the sound. The buzzing noise also occurs if I manually change the brightness to darker than 100%…

  • Now tried a different types of setups:

    • Powering only the Panel over USB
    • Powering Panel and DuetWifi over USB
    • Powering Panel and DuetWifi over 24V

    always the same problem. As my board and panel is brand new, do I have to send it back because it is broken or is this a problem that often occurs?

  • administrators

    I'll check my 7i out tomorrow to see whether I can hear any buzzing. The buzzing sound is caused by the PWM used to modulate the brightness, but it's normally inaudible.

  • administrators

    My own 7i makes a very faint buzzing noise when dimmed, which I can only hear if I put my ear right up to the board or right up to the screen. If your board makes a buzzing noise that you can hear at some distance from it, then it may be faulty. My board is a prototype, so I will ask another member of our team to check out a production board.

    Meanwhile, please can you examine the soldering of UA1 to check that there are no solder bridges between adjacent pins.

  • For me, it looks like UA1 is soldered right… No Pins are bridged... I was running the Panel in my quiet room. As I left and came back, I was wondering that weird sound I heard. At first, I thought the monitor of my pc is broken, but then I realised it was the Panel which was dimmed. As I wrote, the problem also occures if I dimm the panel manually. (Loudest 1 Step below 100% brightness)

  • Already got any solutions on this problem?

  • administrators

    A faint buzzing sound is normal, but it should not be loud enough to be troublesome. If your TFT panel buzzes loudly, ask for it to be replaced.

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