Possible causes of dim Microwave Oven display

Discussion in 'General Electronics Chat' started by Gdrumm, Jun 13, 2013.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    36
    I've seen some Microwave ovens that will not display a backlight anymore. They still work, but the display is so dim, you have to be inches away to read it.

    In my mind, (from one personal experience) it seems to be related to bad weather, lightning in our area. Does that make sense?

    The display LEDs checked out okay, until I fried them just now with a 9v battery.

    Does anyone have any experience to know likely causes?
    (Of the display issue, I know the cause of my frying the LEDs.
    It's called OMS or DA)
    Thanks,
    Gary
     
  2. Meixner

    Member

    Sep 26, 2011
    116
    21
    Maybe you are discribing VF (vacuum flourescent) displays, they are frequently used in microwave ovens and they get dim with age.
     
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    36
    Would they have LEDs mounted to the display?
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,999
    745
    Think yours is an LCD with led back lites.
     
  5. sheldons

    Well-Known Member

    Oct 26, 2011
    616
    101
    depends on the microwave-if its an lcd display type that requires a backlight before you see anything displayed-hi brightness leds are used here and they may be special types used depending on model and manufacturer-if its a vf display sometimes its a low supply/missing supply on the filament or a faulty display itself
     
  6. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I found a leaking cap nearby.
    Anyway, thanks for the feedback.
    Gary
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Yes it is a VFD, and no they don't really get that dim with age, they can be at excellent brightness even after 30 years constant use.

    However they have a very common fault that makes them get very dim, this is because the caps in the 50v inverter circuit get old and reduce the 50v supply.

    Generally they are very easy to return to full brightness. Just get to the PCB and replace any electro caps near the VFD. The inverter caps are usually 63v rated and are near to an inductor of some type (to form a boost inverter).
     
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