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Thread: LCD troubleshooting question

  1. #1
    Newbie
    Join Date
    Oct 1999
    Posts
    9

    LCD troubleshooting question

    I have an Optrex 40x4 that I wired up last night. After I hooked it up, most of the character locations went solid black then slowly faded out. Then when I turned the POT controlling the LCD power (Vlc), it created different block patterns of solid characters. Also, all of the chips on the board got VERY hot, and a paper sticker on one of the chips started to singe brown in the middle. The LED backlighting side of the system works OK, although the lighting looks patchy.
    Does this sound like a problem that any of you have had? I THINK I wired it correctly, but one can never be sure. Did I smoke this piece?? Should I chalk this one up to a learning experience and get a new LCD??

    Please help if you can.
    Thanks,
    -cyalume

  2. #2
    Low Bitrate
    Join Date
    Oct 1999
    Location
    N Ireland
    Posts
    108
    I think that you should chalk this one up to experience :-(

    The LCD power should be fixed at 5V and the pot should be connected to the contrast control pin to set the contrast level. The solid blocks fading out was probably the controller chips burning out . These things generally take very small amounts of power and if they get hot or warm then something is wrong. If the backlight looks patchy then you have probably applied too high a voltage and damaged it.

  3. #3
    Newbie
    Join Date
    Oct 1999
    Posts
    9
    Well, I hooked power directly to a free drive power adapter from the power supply. I am fairly certain I went to the +5V side of it. Could this have been too much power?!?! The LCD's specs show max power around +7v.



  4. #4
    Low Bitrate
    Join Date
    Oct 1999
    Location
    N Ireland
    Posts
    108
    On the disk drive power connectors
    Red is +5V
    Black is Ground
    Yellow is +12V

    If you went between yellow and black thus supplying 12V to the lcd then that would damage it. Or if you connected in reverse or to the wrong pins then that too would fry it

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